C D B A 012/T/001/2000 29.2.2000 15:37:53 E 2000 by Bossard T D C A B E 012/T/001/2000 29.2.2000 15:37:53 E E E Page: Terms and definitions Materials Screws (property classes 3.6 to 12.9) Terminology 2–3 – Mechanical properties 4 – Minimum ultimate tensile loads 5 – Steels for metric screws 6 – Materials, heat treatment, chemical composition 7 – Characteristics at elevated temperatures 7 Nuts (property classes 04 to 12) – Mechanical properties 8 – Minimum bolt stress for nuts ≥ 0,5 d and < 0,8 d 8 – Nut materials 9 – Chemical composition 9 Screws and nuts – Marking 10–11 – Pairing screws and nuts 11 Screws and nuts for high and low temperatures – Table of materials for high and low temperatures 12 – Pairing materials 12 – Reference information for the stat. elasticity module 13 and on the coefficient of thermal expansion – Ductility, yield strenght and tensile strength of 14 steels at high and low temperatures – Elastic elongation, yield strength ReL or R p0,2 15 min. elongation Stainless steel fasteners – Designation of property class acc. to ISO 3506 16 – Chemical composition 16–17 – Distinctive properties A1 / A2 / A4 / A5 17 – Mechanical properties 18 – Minimum breaking torques 18 – Elongation limit (Rp0,2 ) of higher temperatures 19 – Marking of screws and nuts 19 – Corrosion resistance, technical arguments 20 Fasteners made from various materials – Non-ferrous materials 21 – Special materials 22 – Thermoplastics 24–25 Plating and surface treatments – Electrolytic processes 26 – Hydrogen embrittlement, alternatives 26 – Coating thicknesses for parts with external thread 27 – Further galvanic coating processes 28 – Further surface treatments 28 Page: Design Estimation of screw diameters 29 Fatigue resistance – Strength under dynamic load 30 Surface pressure – Surface pressure limits of various materials 30 – Hex cap screws and hexagon nuts 31 – Socket head cap screws 31 Friction coefficient – For bolted joints and µtotal of stainless steel screws 32 Tightening method, tightening factor αA 33 Preload and tightening torques – How to use the torque chart? 34 – Metric coarse thread 35 – Metric fine threads 36 – Screws made from polyamide 36 – Screws made from austenitic steel A1 / A2 / A4 37 – Fasteners with hexagon socket and flat heads 37 – Locking screws and nuts, flange screws and nuts 38 – High–strength structural steel bolts (HV sets) 39 Locking methods – Constructive measures 40 – Locking elements 41 Shear loads for pins – Single and double – lap joints 42 Design recommendations – Thread forming screws for metals 43 – Thread forming screws for thermoplastics 44–45 – Self tapping screws for sheet metals 46 – Sheet metal joints 47 – Threaded inserts Ensat 48–49 – Internal drives for screws 50–51 Metric ISO threads – Basic concept, clearance fit, tolerance fields 52 – Limits for metric (standard) coarse threads 53 – Limits for metric fine threads 54 – Preference classes, drill size 55 – Nominal dimensions 56 Tables / tolerances / standards – ISO-Tolerances 57–58 – Basic tolerances and tolerance fields 59 – SI units system and conversion tables 60–61 – Conversion tables: metric – USA, USA – metric 62–63 – Table of hardness comparisons 64 – National standards 65 Table of Contents T T
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Page:
Terms and definitionsMaterials
Screws (property classes 3.6 to 12.9)Terminology 2–3– Mechanical properties 4– Minimum ultimate tensile loads 5– Steels for metric screws 6– Materials, heat treatment, chemical composition 7– Characteristics at elevated temperatures 7
Nuts (property classes 04 to 12)– Mechanical properties 8– Minimum bolt stress for nuts ≥ 0,5 d and < 0,8 d 8– Nut materials 9– Chemical composition 9
Screws and nuts– Marking 10–11– Pairing screws and nuts 11
Screws and nuts for high and low temperatures– Table of materials for high and low temperatures 12– Pairing materials 12– Reference information for the stat. elasticity module 13 and on the coefficient of thermal expansion– Ductility, yield strenght and tensile strength of 14 steels at high and low temperatures– Elastic elongation, yield strength ReL or Rp0,2 15 min. elongation
Stainless steel fasteners– Designation of property class acc. to ISO 3506 16– Chemical composition 16–17– Distinctive properties A1 / A2 / A4 / A5 17– Mechanical properties 18– Minimum breaking torques 18– Elongation limit (Rp0,2) of higher temperatures 19– Marking of screws and nuts 19– Corrosion resistance, technical arguments 20
Fasteners made from various materials– Non-ferrous materials 21– Special materials 22– Thermoplastics 24–25
Plating and surface treatments
– Electrolytic processes 26– Hydrogen embrittlement, alternatives 26– Coating thicknesses for parts with external thread 27– Further galvanic coating processes 28– Further surface treatments 28
Page:
Design
Estimation of screw diameters 29
Fatigue resistance– Strength under dynamic load 30
Surface pressure– Surface pressure limits of various materials 30– Hex cap screws and hexagon nuts 31– Socket head cap screws 31
Friction coefficient– For bolted joints and µtotal of stainless steel screws 32
Tightening method, tightening factor αA 33
Preload and tightening torques– How to use the torque chart? 34– Metric coarse thread 35– Metric fine threads 36– Screws made from polyamide 36– Screws made from austenitic steel A1 / A2 / A4 37– Fasteners with hexagon socket and flat heads 37– Locking screws and nuts, flange screws and nuts 38– High–strength structural steel bolts (HV sets) 39
Locking methods– Constructive measures 40– Locking elements 41
Shear loads for pins– Single and double – lap joints 42
Design recommendations– Thread forming screws for metals 43– Thread forming screws for thermoplastics 44–45– Self tapping screws for sheet metals 46– Sheet metal joints 47– Threaded inserts Ensat 48–49– Internal drives for screws 50–51
Metric ISO threads
– Basic concept, clearance fit, tolerance fields 52– Limits for metric (standard) coarse threads 53– Limits for metric fine threads 54– Preference classes, drill size 55– Nominal dimensions 56
Tables / tolerances / standards
– ISO-Tolerances 57–58– Basic tolerances and tolerance fields 59– SI units system and conversion tables 60–61– Conversion tables: metric – USA, USA – metric 62–63– Table of hardness comparisons 64– National standards 65
Table of Contents
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Terminology
Tensile strength Rm [N/mm2]The minimum tensile strength of a screw is the tensile stressfrom which there could be a rupture in the shank or the thread(not in the head/shank joint). If full size screws are tested, the yield strength can only beapproximately established. Under ISO 898 Part 1, the exactyield strength and elongation after fracture can only bedetermined using machined samples. Exceptions are stain-less steel screws A1–A4 (ISO 3506).
Tensile strength at rupture in thread:
max. tensile force F Nstress area As mm2
(Stress area As [mm2] of thread, see T.031)
Tensile strength at rupture in cylindrical shank:
max. tensile force F Ncylindrical starting cross–section mm2
Yield strength Rel [N/mm2]The yield strength is the tensile stress from which elongationbegins to increase disproportionately with increasing tensileforce. A plastic elongation remains after relief.
R m =
R m =
0,2 limit Rp0,2 [N/mm2]The yield strength of harder material is difficult to determine.The 0,2 limit is defined as the tensile stress from which aplastic elongation of exactly 0,2% remains after relief.
In practice, screws may be stressed by tightening and underworking load no more than up to the yield strength or the 0,2limit.
Elongation at fracture A5 [%]This occurs on loading up to the rupture point of the screw. Ina defined shank area, the remaining plastic elongation isdetermined using machined screws. Exceptions: screws A1–A4, where this is measured on fullsize screws (ISO 3506).
do
measuring length
Lo = 5 x do
0.2
limit
Rp
0,2
tens
ile fo
rce
max
. ten
sile
forc
e
elongation
F
Tensile test on fullsize screw
Tensile test on machined screw
max
. ten
sile
fo
rce
yiel
d po
int
elongation
tens
ile fo
rce
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Wedge tensile strengthThe tensile strength on whole screws is established and thehead strength simultaneously tested on an angular load. Therupture must not occur in the head/shank joint.
Terminology
Hardness Generally speaking hardness is the resistance which thematerial offers to the penetration of a test body under adefined load (see ISO 898, Part 1).Hardness comparison tables, see T.064.
Vickers hardness HV: ISO 6507 Test body: Pyramid (encompasses the complete hardness
range usual for screws).
Brinell hardness HB: ISO 6506 Test body: BallRockwell hardness HRC: ISO 6508 Test body: Cone
Impact strength (Joule) ISO 83is the impact work used in the notched bar impact bendingtest. A notched sample is taken from near the surface of thescrew. This sample is broken with a single blow in apendulum ram impact testing machine, yielding information onthe microstructure, melting behaviour, inclusion content, etc..The measured value cannot be included in design calcula-tions.
Surface defects are slag inclusions, material overlaps and grooves stemmingfrom the raw material.Cracks, on the other hand, are crystalline ruptures without in-clusions. For details, see DIN 267 Part 20, ISO 6157.
Decarburization of the surfaceis generally a reduction in the carbon content of the surface ofthe thread of heat treated screws, see ISO 898 Part 1.
F
Head soundness The head of the screw must withstand several hammer blows.After being bent to a specified angle, the shank head filletshall not show any signs of cracking. For details see ISO 898,part 1.
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ScrewsProperty classes3.6 to 12.9
Property class Sub-clause Mechanical and physical property 3.6 4.6 4.8 5.6 5.8 6.8 8.81) 9.82) 10.9 12.9
number d ≤ 163) d > 163)
mm mm5.1 and Tensile strength nominal value 300 400 500 600 800 800 900 1000 12005.2 Rm
4),5) in, N/mm2 min. 330 400 420 500 520 600 800 830 900 1040 12205.3 Vickers hardness HV min. 95 120 130 155 160 190 250 255 290 320 385
F ≥ 98 N max. 220 6) 250 320 335 360 380 4355.4 Brinell hardness HB min. 90 114 124 147 152 181 238 242 276 304 366
N/mm2 180 225 310 280 380 440 580 600 650 830 9705.10 Breaking torque, MB Nm min. — See ISO 898-75.11 Percent elongation after fracturemin. 25 22 — 20 — — 12 12 10 9 8
A in %5.12 Reduction area after fracture, Z % min. — 52 48 48 445.13 Strength under wedge The values for full size bolts and screws (not studs) shall not be
loading5) smaller than the minimum values for tensile strength shown in 5.25.14 Impact strength, KU min. J — 25 — 30 30 25 20 15
in J5.15 Head soundness no fracture5.16 Minimum height of non-decarburized — 1/2 H1
2/3 H13/4 H1
thread zone, EMaximum depth of mm — 0,015complete decarburization, G
5.17 Hardness after retempering — Reduction of hardness 20 HV maximum5.18 Surface integrity In accordance with ISO 6157-1 or ISO 6157-3 as appropriate
1) For bolts of porperty class 8.8 in diameters d ≤ 16 mm, there is an increased risk of nut stripping in the case of inadvertent over-tightening inducing a load in excess of proofing load. Reference to ISO 898-2 is recommended.
2) Applies only to nominal thread diameters d ≤ 16 mm.3) For structural bolting the limit is 12 mm. 4) Minimum tensile properties apply to products of nominal length I ≥ 2,5 d. Minimum hardness applies to products of length l <2,5 d and other
products which cannot be tensile-tested (e.g. due to head configuration).5) When testing full-size bolts, screws and studs, the tensile loads, which are to be applied for the calculation of Rm shall meet the values given
on page T.005.6) A hardness reading taken at the end of bolts, screws and studs shall be 250 HV, 238 HB or 99,5 HRB maximum.7) Surface hardness shall not be more than 30 Vickers points above the measured core hardness on the product when readings of both surface and core
carried out at HV 0,3. For property class 10.9, any increase in hardness at the surface which indicates that the surface hardness exceeds 390 HV is not acceptable.
8) In cases where the lower yield stress Rel cannot be determined, it is permissiblr to measure the stress at 0,2 % non-proportional elongation Rp 0,2. For the property classes 4.8, 5.8 and 6.8 the values for Rel are given for calculation purposes only, they are not test values.
9) The yield stress ratio according to the designation of the property class and the minimum stress at 0,2 % non-proportional elongation Rp 0,2 apply tomachined test specimens. These values if received from tests of full size bolts and screws will vary because of processing method and size effects.
min.
max.
The mechanical properties are given for tests at room temperature.
Mechanical and physical properties ofbolts, screws and studsaccording to ISO 898 – part 1
4.8 QSt 36–2 = 1.0203 ÷ 9 S 20 = 1.0711 commonly to none ÷ noneQSt 38–2 = 1.0204 to M16
5.6 Cq 22 = 1.1152 St 50–2 = 1.0533 ÷ to M39 annealed ÷ 5.8 Cq 22 = 1.1152 ÷ 9 SMn 28 = 1.0715 to M39 none ÷ none or
Cq 35 = 1.1172 10 S 20 = 1.0721 tempered 6.8 Cq 35 = 1.1172 C 45 = 1.0503 10 S 20 = 1.0721 to M39 none or quenched and none or
35 B 2 = 1.5511 46 Cr 2 = 1.7006 quenched and tempered quenched andCq 45 = 1.1192 tempered tempered
8.8 22 B 2 = 1.5508 not common to M1228 B 2 = 1.5510
8.8 35 B 2 = 1.5511 C 45 = 1.0503 to M22Cq 35 = 1.1172 46 Cr 1 = 1.7002Cq 45 = 1.119234 Cr 4 = 1.7033 46 Cr 2 = 1.7006 from M2437 Cr 4 = 1.7034 to M39
10.9 35 B 2 = 1.5511 to M6Cq 35 = 1.117234 Cr 4 = 1.7033 not or from M8 quenched and tempered
41 Cr 4 = 1.7035 not very common to M1841 Cr 4 = 1.7035 to M3934 CrMo 4 = 1.722042 CrMo 4 = 1.7225
12.9 34 CrMo 4 = 1.7220 to M1837 Cr 4 = 1.703441 Cr 4 = 1.703542 CrMo 4 = 1.7225 to M2434 CrNiMo 6 = 1.6582 to M39
ISO 898 Part 1 only applies for screws with nominal diameters up to M39. Screws with larger diameters can be manufactured fromthe same steels indicated for use up to M39, but the mechanical properties must meet the requirements of ISO 898 – part 1.
Steels for metric screwsaccording to manufacturers' specifications
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ScrewsProperty classes3.6 to 12.9
Chemical composition limits TemperingProperty Material and heat treatment (check analysis) % temperatureclass C P S B1) °C
8.83) Carbon steel with additives (e.g. Boron, Mn or Cr)quenched and tempered 0,154) 0,40 0,035 0,035 0,003or 425cabon steel, quenched and tempered 0,25 0,55 0,035 0,035
9.8 Carbon steel with additives (e.g. Boron, Mn, or Cr),quenched and tempered 0,154) 0,35 0,035 0,035 0,003or 425carbon steel, quenched and tempered 0,25 0,55 0,035 0,035
10.95), 6) Carbon steel with additives(e.g. Boron, Mn or Cr), quenched and tempered 0,154) 0,35 0,035 0,035 0,003 340
10.96) Carbon steel, quenched and tempered 0,25 0,55 0,035 0,035 0,003orcarbon steel with additives(e.g. Boron, Mn or Cr), quenched and tempered, 0,204) 0,55 0,035 0,035 425oralloyed steel, quenched and tempered 7) 0,20 0,55 0,035 0,035
12.96),8),9) Alloyed steel, quenched and tempered 7) 0,28 0,50 0,035 0,035 0,003 3801) Boron content can reach 0,005 % provided that non-effective boron is controlled by addition of titanium and/or aluminium.2) Free cutting steel is allowed for these property classes with the following maximum sulfur, phosphorus and lead contents:
sulfur 0,34%, phosphorus 0,11%, lead 0,35% 3) For nominal diameters above 20 mm the steels specified for property class 10.9 may be necessary in order to achieve
sufficient hardenability. 4) In case of plain carbon boron alloyed steel with a carbon content below 0,25% (ladle analysis), the minimum manganese content shall be 0,6%
for property class 8.8 and 0,7% for 9.8 and 10.95) Products shall be additionally identified by underlining the symbol of the property class (see page T.010).6) For the materials of these property classes, it is intended that there should be a sufficient hardenabiltity to ensure a structure consisting of
approximately 90% martensite in the core of the threaded sections for the fasteners in the «as-hardened» condition before tempering.7) This alloy steel shall contain at least one of the following elements in the minimum quantity given: chromium 0,30 %, nickel 0,30 %, molybdenum
0,20 %, vanadium 0,10 %. Where elements are specified in combinations of two, three or four and have alloy contents less than those given above,the limit value to be applied for class determination is 70 % of the sum of the individual limit values shown above for the two, three or four elementsconcerned.
8) A metallographically detectable white phosphorous enriched layer is not permitted for property class 12.9 on surfaces subjected to tensile stress. 9) The chemical composition and tempering temperature are under investigation.
Carbon steel
Materials, heat treatment, chemical compositionsaccording to ISO 898 – part 1
Characteristics at elevated temperaturesaccording to ISO 898 – part 1
TemperatureProperty class +20 °C +100 °C +200 °C + 250 °C + 300 °C
Continuous operating at elevated service temperature may result in significant stress relaxation. Typically 100 h service at 300 °C willresult in a permanent reduction in excess of 25 % of the initial clamping load in the bolt due to decrease in yield stress.
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NutsProperty classes04 to 12
Mechanical properties of nuts with coarse (standard) threads according to ISO 898 – part 2
The standard values for strip resistance relate to the given bolt classes.The exterior thread may be expected to strip if the nuts are paired with screws of lover property classes, while the thread of the nutwill strip if it is paired with screws of higher property classes.
2951)
Property class Proof Minimum stress in the core of bolt when stripping occursof nut load stress for bolts with property class
of the nut N/mm2
For bolts with property classN/mm2 6.8 8.8 10.9 12.9
04 380 260 300 330 35005 500 290 370 410 480
3531) 2722) 3532)
2) Nuts style 2 (ISO 4033)
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Property class Chemical composition (check analysis) %C Mn P Smax. min. max. max.
1) Nuts of these property classes may be manufactured from free-cutting steel unless otherwise agreedbetween the purchaser and the manufacturer. In such cases, the following maximum sulfur, phospho-rus and lead contents are permissible:
sulfur 0,34%phosphorus 0,11%lead 0,35%
2) Alloying elements may be added, if necessary, to develop the mechanical properties of the nuts.
NutsProperty classes04 to 12
Nut materials according to manufacturers' specifications
Chemical compositions of nutsaccording to ISO 898 – part 2
Property Raw materials for fabrication by Nut Final condition of nut class diameter
cold–forming hot–forging machining formed machinedUQSt 36–2 UST 36–2 St 34–2 no subsequent no subsequent1.0204 1.0203 1.0151 treatment treatment
St 37–2 4, 5, 6 1.0161
35S 20 k1.07269S 20 k1.0711
UQSt 36–2 C 22 1.0402 35 S 20 k ≤ M 16 8 Cq 22 C 35 1.0501 1.0726
Cq 35 45 S 20 k > M 16 quenched and1.0727 tempered
10, 12 Cq 35 C 35 1.0501 C 35 1.0501 quenched andCq 45 C 45 1.0503 C 45 1.0503 tempered
Nuts of property classes 05, 8 (style 1 > M 16), 10 and 12 must be hardened and tempered.
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ScrewsBoltsNuts
Marking of screws and boltsaccording to ISO 898 – part 1
1) The full-stop in the marking symbol may be omitted.2) When low carbon martensitic steels are used for property class 10.9 (see table on page T.007),
the symbol 10.9 shall be underlined: 10.9
Identification with the manufacturer's mark and the property class is mandatory for hexagon screws 3.6 to 12.9 and sockethead cap screws 8.8 to 12.9 with thread diameter d ≥ 5 mm, where the shape of the screw always allows it – preferably onthe head.
Marking of studsaccording to ISO 898 – part 1
Identification with the manufacturer is mark and property class is mandatory for hexagon nuts with thread diameter d ≥ 5 mm. Thehexagon nuts must be marked with an indentation on the bearing surface or on the side or by embossing on the chamfer. Embossedmarkings must not protrude beyond the bearing surface of the nut.
Example of marking with the designation symbol. Example of marking with the code symbol (clock-face sy-stem).
Example of marking with the property class designation symbol.
Example of marking with the code symbol (clock-face system)
Property class 5.6 8.8 9.8 10.9 12.9
Marking symbol
Marking is obligatory for property classes of or higher than 8.8 and is preferably to be made on the threaded part by an indentation.For adjustment bolts with locking, the marking must be on the side of the nut.Marking is required for bolts of nominal diameter of or greater than 5 mm.
The symbols shown in the table on the right are also authorised as a method of identification.
8.8
AB
8
8AB
ABAB
Marking of nuts according to ISO 898 – part 2
Examples of marking on hexagon screws. Examples of marking on socket head cap screws and hexalobularhead bolts and screws.
ABCD
8.8
ABCD 8.8
ABCD
12.9
ABCD 12.9
8.8
XY
Z
XYZ
8.8
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ScrewsBoltsNuts
Marking of nuts according to DIN 267 – part 4
For hexagon nuts with nominal thread diameter d ≥ 5 mm acc. to DIN 934 and DIN 935 made from free-cutting steel, the markingmust also include a groove on one chamfer of the nut (up to property class 6).
Hexagon nuts with nominal thread diameter d ≥ 5 mm must be marked with the property class on the bearing surface or on the side.Embossed markings must not protrude beyond the bearing surface of the nut.
Groove
|8|
|8|
Pairing screws and nuts ≥ 0,8daccording to ISO 898 – part 2
Assignment of possible property classes of screws and nuts
Property class Mating bolts Nutsof nut Type 1 Type 2
Property class Diameter range Diameter range 4 3.6 4.6 4.8 > M16 > M16 — 5 3.6 4.6 4.8 ≤ M16
Remark: In general, nuts of a higher property class are preferable to nuts of a lower property class. This is advisable for a bolt / nut assembly stressed higher than the yield stress or the stress under proof load.
≤ M39 —
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Screws and nuts forhigh and low temperatures
Table of materials for high temperaturesaccording to DIN 267, part 13
Pairing materials for screws and nutsaccording to DIN 267, part 13
Material Material number Marking Utilisationabbreviation temperatur limits
C 35 N ou C 35 V 1.0501 Y +350 °CCk 35 1.1181 YK +350 °C35 B 2 1.5511 YB +350 °C24 CrMo 5 1.7258 G +400 °C21 CrMoV 5 7 1.7709 GA +540 °C40 CrMoV 4 7 1.7711 GB +500 °CX 22 CrMoV 12 1 1.4923 V, VH +580 °CX 19 CrMoVNbN 11 1 1.4913 VW +580 °CX 8 CrNiMoBNb 16 16 1.4986 S +650 °CX 5 NiCrTi 26 15 1.4980 SD +650 °CNiCr20 TiAl 2.4952 SB +700 °C
MaterialScrew Nut
Ck 35 C 35 N, C 35 V, Ck 35, 35 B 235 B 224 CrMo 5 Ck35, 35 B 2, 24 CrMo 521 CrMoV 5 7 24 CrMo 5
21 CrMoV 5 740 CrMoV 4 7 21 CrMoV 5 7X 22 CrMoV 12 1 X 22 CrMoV 12 1X 19 CrMoVNbN 11 1X 8 CrNiMoBNb 16 16 X 8 CrNiMoBNb 16 16X 5 NiCrTi 26 15 X 5 NiCrTi 26 15NiCr 20 TiAl NiCr 20 TiAl
Table of materials for low temperaturesfrom –200 °C to –10 °Caccording to DIN 267, part 13
Material Material number Marking Utilisationabbreviation temperatur limits
1) The steels of these material groups are shown with their material number.
Material Material Density Coefficient of heat expansion between 20 °C andabbreviation number at 20 °C 100 °C 200 °C 300 °C 400 °C 500 °C 600 °C 700 °C 800 °C
Stainless steelfastenersDesignation of property classes
according to ISO 3506
Composition groups
FiIdentification of steelgrades
Screws, nuts style 1
Ferritic
45 60
020 030
MartensiticAustenitic
80
040
C3
50 70
035
110
055
7050
025
C4C1A4A31)A2A1 A51)
80
040
70
035
50
025Flat nuts
Property classes
soft work-hardened
heavilywork-hardened
soft hardended +tempered
soft hardened +tempered
hardended +tempered
soft work-hardened
035 025
Descriptions using a letter/figure combination mean the following:
A2 – 70
Abbreviation of composition group:A = austenitic chromium-nickel steel
Abbreviation of chemical composition:1 = free-cutting steel with sulphur additive2 = cold-heading steel alloyed with chromium and nickel3 = cold-heading steel alloyed with chromium and nickel,
stabilised with Ti, Nb, Ta4 = cold-heading steel alloyed with chromium, nickel and
molybdenum5 = cold-heading steel alloyed with chromium, nickel and
molybdenum, stabilised with Ti, Nb, Ta
Abbreviation of property class:50 = 1/10 of tensile strength of screw/proofstress for nuts (min. 500 N/mm2)70 = 1/10 of tensile strength of screw/proofstress for nuts (min. 700 N/mm2)80 = 1/10 of tensile strength of screw/proofstress for nuts (min. 800 N/mm2)
Flat nuts:025 = proof stress for nuts (min. 250 N/mm2)035 = proof stress for nuts (min. 350 N/mm2)040 = proof stress for nuts (min. 400 N/mm2)
Chemical composition of austenitic stainless steels according to ISO 3506More than 97% of all fasteners made from stainless steels are produced from this steel composition group. They are characterised byimpressive corrosion resistance and excellent mechanical properties.Austenitic stainless steels are divided into 5 main groups whose chemical compositions are as follows:
Steel Chemical composition in % (maximum values, unless otherwise indicated, rest iron (Fe))group C Si Mn P S Cr Mo Ni CuA1 0,12 1,0 6,5 0,200 0,15–0,35 16–19 0,7 5–10 1,75–2,25A2 0,10 1,0 2,0 0,050 0,03 15–20 — 8–19 4A31) 0,08 1,0 2,0 0,045 0,03 17–19 — 9–12 1A4 0,08 1,0 2,0 0,045 0,03 16–18,5 2–3 10–15 1A51) 0,08 1,0 2,0 0,045 0,03 16–18,5 2–3 10,5–14 1
1) stabilised against intergranular corrosion through addition of titanium, possibly niobium, tantalum.
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Stainless steelfastenersChemical composition
Steel Comparable C Si Mn P S Cr Mo Nigroup steels under
DIN 17440Number % % % % % % % %
Ferritic steelsF1 1.40061) 0,10 1,0 1,0 0,040 0,030 16,0 up to 18,0 — ≤ 0,50F1 — 4) 0,10 1,0 1,0 0,040 0,030 16,0 up to 18,0 — ≤ 0,50F1 — 0,10 1,0 1,0 0,040 0,030 16,0 up to 18,0 0,90 up to 1,30 —
Martensitic steelsC1 1.40061) 0,09 up to 0,15 1,0 1,0 0,040 0,030 11,5 up to 14,0 — ≤ 1,0C4 — 2) 0,08 up to 0,15 1,0 1,5 0,060 0,150 up to 0,350 12,0 up to 14,0 0,60 max. ≤ 1,0C1 1.4021 0,16 up to 0,25 1,0 1,0 0,040 0,030 12,0 up to 14,0 — ≤ 1,0C3 — 0,10 up to 0,20 1,0 1,0 0,040 0,030 15,0 up to 18,0 — 1,5 bis 3,0C3 1.40571) 0,17 up to 0,25 1,0 1,0 0,040 0,030 16,0 up to 18,0 — 1,5 bis 2,5C1 1.40283) 0,26 up to 0,35 1,0 1,0 0,040 0,030 12,0 up to 14,0 — ≤ 1,0C1 1.4034 0,36 up to 0,45 1,0 1,0 0,040 0,030 12,5 up to 14,5 — ≤ 1,0C1 — 0,42 up to 0,50 1,0 1,0 0,040 0,030 12,5 up to 14,5 — ≤ 1,0
Austenitic steelsA2 1.4306 0,030 1,0 2,0 0,045 0,030 17,0 up to 19,0 — 9,0 up to 12,0A2 1.4301 0,070 1,0 2,0 0,045 0,030 17,0 up to 19,0 — 8,0 up to 11,0A1 1.43051) 0,120 1,0 2,0 0,045 0,150 up to 0,350 17,0 up to 19,0 0,60 max. 8,0 up to 10,0A2 1.43031) 0,100 1,0 2,0 0,045 0,030 17,0 up to 19,0 — 11,0 up to 13,0A3 1.45411), 4) 0,080 1,0 2,0 0,045 0,030 17,0 up to 19,0 — 9,0 up to 12,0A3 1.4550 5) 0,080 1,0 2,0 0,045 0,030 17,0 up to 19,0 — 9,0 up to 12,0A4 1.4404 0,030 1,0 2,0 0,045 0,030 16,0 up to 18,5 2,0 up to 2,5 11,0 up to 14,0A4 1.44011) 0,070 1,0 2,0 0,045 0,030 16,0 up to 18,5 2,0 up to 2,5 10,5 up to 14,0A5 1.45711), 4) 0,080 1,0 2,0 0,045 0,030 16,0 up to 18,5 2,0 up to 2,5 10,5 up to 14,0A5 1.4580 5) 0,080 1,0 2,0 0,045 0,030 16,0 up to 18,5 2,0 up to 2,5 10,5 up to 14,0A4 1.4435 0,030 1,0 2,0 0,045 0,030 16,0 up to 18,5 2,5 up to 3,0 11,5 up to 14,5A4 1.4436 0,070 1,0 2,0 0,045 0,030 16,0 up to 18,5 2,5 up to 3,0 11,0 up to 14,51) Mainly used in Europe. 2) In Europe free-cutting steel 13 CrMoS 17 (material number 1.4104) is preferred.3) According to: «Stahl-Eisen-Werkstoffblatt 400».4) With addition of Ti: 5x% C ≤ Ti ≤ 0,805) With addition of Nb: 10x% C ≤ Nb ≤ 1,0
A1: for machining, conditionally rust- and acid-resistantA2: standard qualityA4: highest corrosion resistance (with molybdenum additive)
– spring parts made from martensitic chrome steel C1, C2, C3have lower corrosion resistance than A2, A4
A3, A5: as for A2, A4, however stabilised against intergranular corrosion after welding or annealing
see also page T.020
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Stainless steelfasteners
Mechanical properties for fasteners made from austenitic stainless steel according to ISO 3506- part 1 bolts, screws and studs/- part 2 nuts
ScrewsThread Tensile Stress at 0,2% Elongation after
Group Grade Property diameter strength R m1) permanent strain fracture
class of range N / mm 2 R p 0,21) A2)
screw d min. min. min.N / mm 2 mm
A1, A2 50 ≤ M 39 500 210 0,6 dAustenitic A3, A4 70 ≤ M 203) 700 450 0,4 d
A5 80 ≤ M 203) 800 600 0,3 d
Property class 70 – commercial:
The values of property classes 70 and 80 apply only for cold formed fasteners with diameters conforming to the above table andlengths up to 8xd, such as hexagon, hexagon socket, slotted, recessed and locking screws.
Property class 70 is commercial and usually also the most economic.
Screws of property class 80 are only advised if the components are also manufactured from high-strength stainless steel which isnot often so. The component is machined, the work-hardened surface zone is usually removed and the screw head then contacts thesoft core material.
For manufacturing reasons, fasteners of A2, A4 over M20 or with lengths greater than 8xd usually have lower strengths in the class50 range. If higher strengths are needed, this must be made clear when ordering.
For additional information, see Technical Information 3: Stainless steel fasteners. Please ask for a copy!
Minimum breaking torques for screws M1,6 to M16(coarse thread) according to ISO 3506 - part 1
NutsProperty class Thread Stress under proof load Sp
of nuts diameter N / mm2
Group Grade range min.nut thin nuts d nuts thin nuts
style 1 style 1m ≥ 0,8d 0,5 d ≤ m < 0,8 d [mm] m ≥ 0,8d 0,5 d ≤ m < 0,8 d
1) The tensile stress is calculated on the stress area.2) To be determined according to the actual screw length and not on a prepared test piece; d is the nominal thread diameter.3) For fasteners with nominal thread diameters d > 24 mm the mechanical properties shall be agreed upon between user and manu-
facturer and marked with grade and property class according to this table.
Elongation limit (Rp0,2) at elevated temperatures as % of the values at room temperature according to ISO 3506
Rel and Rp 0,2 in %
Steel grade +100 °C +200 °C +300 °C +400 °C
A2, A4 85% 80% 75% 70% applies for property classes 70 and 80
Marking of screws and nuts according to ISO 3506
RequirementScrews and nuts made from stainless austenitic steels mustbe marked.
ScrewsHexagon and hexagon socket screws from nominal diameterM5 must be marked. The marking must show the steel group,the property class and the manufacturer's mark.
Locking screwsmust be marked on the shaft or screw end.
BoltsBolts from nominal diameter M5 must be marked on theshank or the end of the thread with the steel group, the pro-perty class and the manufacturer's mark.
Hexagon screws manufacturer'smark
steel group propertyclass
Socketheadcap screw
Nuts
Alternativegroove marking
NutsNuts from minimal diameter M5 must be marked with the steelgroup, the property class and the manufacturer's mark.
XYZ
A2-70
XYZ A2-70
XYZ
A2-70
XYZ
A2–50
A2
∅ >
s
A4
Caution!Only those fasteners marked to standard will have the desired properties. Products not marked to standard will often only correspond to property classes A2–50 or A4–50
XYZ
A2–50
For applicability at low temperatures, see T.012.
Studs8.8
A2-
70
XY
Z
A4
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Stainless steelfastenersCorrosion resistance
according to manufacturer's information
Austenitic stainless steels have an invisible self-protecti-ve oxide film; if damaged, this film will restore itself as long asthere is oxygen in the vicinity. However, if the access of oxygenis hampered by unfavorable designs or contamination, stainlesssteels will corrode.
Avoid: slits, gaps, humidity concentration bad ventilation and dirt deposits
Rule of thumb: A2 above water, continental climateA4 under water, coastal climateA1 has a small amount of sulphur added,
to improve machinabiltiy. Corrosion resistance less than A2.This also applies to steels C1-C4.
Coatings and black oxidizing (no access to oxygen) aswell as roughening of the surface, reduce corrosion resistance.Under certain conditions, chlorine bearing mediums may causeintergranular corrosion, which may result in a sudden failure ofcomponents.
Standard ISO 3506 specifies steels resistant to corrosionand acids, indicates the corresponding mechanical characteri-stics also the chemical compositions together with some recom-mendations for the appropriate choice of a steel, also in the ca-se of utilisation at low or high temperatures.
The reference data with respect to corrosionresistance should preferably be the results of laboratorytests or practical experience! We gladly provide you withspecimens in order to carry out such tests.
Avantages Prevents the following problems
Bright surface, good appearance Rusting screws give a poor impression. The customer loses confidence in the product.
Safety Corrosion reduces the stability and functionality of the fastening elements. They become weak points.
No red rust Some plastic or textile elements can become unusable due to contact with red rust.
No health risk Blood poisoning can result from injuries from rusty elements.
Utilisation for foodstuffs Galvanised elements must never come into contact with foodstuffs.
No risk from sucking Small children must not suck galvanised or cadmium plated elements.
Easy to clean, hygienic Corrosive products which are difficult to eliminate form on bright or galvanised parts.
Nickel-chrome steel has low Magnetic fastening elements can upset measuring instruments. Magnetic parts attract metallic dust. Othermagnetism corrosion problems occur.
High resistance to elevated The chromating of galvanised, chromated fastening elements deteriorates after 80 °C. Corrosion resistancetemperatures falls considerably.
The screws and nuts are bright and If the thickness of the coating of galvanised screws is excessive, the elements can jam on assembly.always easy to assemble
No problems during maintenance Rusting screws and nuts are difficult to loosen. It is sometimes necessary to damage them, which is generallywork problematic. Elements of the construction are often damaged.
More information is contained in our Technical information Subject B2: Corrosion resistant assemblies. Send for it!
Technical arguments for the utilisation of elements of nickel-chromeaustenitic steel resistant to corrosion A1, A2, A4.
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Fasteners ofvarious materials
Non-ferrous materials according to ISO 8839
Material Nominal thread diameter Tensile Stress at Elongationd strength permanent set limit after fracture
Rm Rp 0,2 ADIN No. Symbol Abbreviation Designation min. min. min.
NiMo 301) ≤ ≤ 26 ≤ 4Hastelloy 2.4810 L 320 750–1000 35 70 residue 2,5 1 to 0,05 0,5 to 1
B 30 6NiMo 16Cr 15 W1) ≤ 14,5 15 3 ≤ 4,5Hastelloy 2.4819 L 310 700– 950 35 85 residue 2,5 to to to 0,01 0,05 to 1
C-276 16,5 17 4,5 7
Fasteners ofvarious materialsSpecial materials
according to manufacturers‘ information
Material Utilisation and particularly noteworthy characteristics.designationMonel 400 Optimal corrosion resistance and strength characteristics.K Monel Also suitable for pressed and forged parts.Inconel 600 Good strength characteristics, low thermal conductivity, excellent corrosion resistance and impressive oxidation resistance at hig
temperatures up to approx. 1100 °C, also in atmospheres with low sulphur content, i.e up to 0,5 gr sulphur per m3.Corronel 220 Impressive corrosion resistance, economically viable in areas where parts come into contact
with hydrochloric acid, but also with sulphuric acid and phosphoric acid.Nimonic 80 A Good long term meat resistance up to 850 °C and very good oxidation resistance at variable elevated temperatures.
Nimonic 90 For high mechanical stress at temperatures up to approx. 900 °C.Nimonic 105 For high mechanical stress at temperatures up to approx. 1000 °C.Incoloy alloy 825 Very good corrosion resistance, even for example
sulphuric acid, phosphoric acid, nitric acid, dilated acids and many others.Nicrofer 4221 See Incoloy alloy 825 above.X 10 Ni Cr Mo Cu 4221Inconel alloy X 750 See Nimonic 80 A above.Pyrotherm- Heat-resisting steel, up to 1200 °C, good corrosion resistance. This steel can be used in25/45/SW atmospheres with up to 1 g sulphur / m3.Resistin-Bronze Seawater-resistant, tough, good thermal strength characteristics up to 450 °C, good cold-toughness.Silverin See Monel 400
or ASTM B 164 Cl.A.Titan Suitable for constructions with high stress, weight savings and good mechanical and chemical resistance.
Hastelloy B Highly corrosion-resistant, used in chemical engineering resistant to deoxydants. Largely resistant to hydrochloric acid, sulphuric acid and phosphoric acid also hydrochloric gas and alkaline solutions. Adequately resistant to oxidising and reducing gases up to 800 °C. Hastelloy B is not recommended for strongly oxidising agents, ferric salt and cupric salts. Hastelloy C quality is more suitable for such stress.
Hastelloy C A nickel/molybdenum/chromium/tungsten alloy, one of the most corrosion-resistant alloys ever developed; it is particularly resistant to bleach solutions which contain free chlorine, chlorites, hypochlorites, sulphuric acid, phosphoric acid and organicacids such as acetic acid, formic acid, solutions of nitrates, sulphates and sulphites, chlorine and chlorates, chromatesand cyanogen compounds etc.
Reference values of physical characteristics according to manufacturer's data
Spe
cific
res
ista
nce
Ω c
m
DIN
534
82
Sur
face
res
ista
nce
Ω DIN
534
82
Mat
eria
l
abb
revi
atio
n
DIN
772
8
Mat
eria
l
abb
revi
atio
n
DIN
772
8
Abbreviation/significancePE-HD High density polyethylenePE-LD Low density polyethylenePP PolypropylenePOM Polymethylene, polyacetatePA 6 PolyamidePA 66 Polyamide
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Fasteners ofvarious materials
Thermoplastics
Waterabsorption, %ASTM D 570
PE-HD 0 0 0 0 1 7 0 0 0 1 0 7 < 0,01
PE-LD 0 0 7 1 7 0 0 0 1 0 1 < 0,01
PP 0 0 0 7 1 7 0 0 0 7 0 1 0,01 à 0,03
POM 0 0 7 1 1 1 0 0 0 1 0 0 0,22 à 0,25
PA 6 0 7 1 1 1 1 0 7 0 1 0 7 1,3 à 1,9
Wat
er, c
old
Wat
er, h
ot
Aci
ds, d
ilute
Aci
ds, s
tron
g
Aci
ds, o
xidi
sed
Aci
d, h
ydro
fluor
ic
Det
erge
nts,
wea
k
Det
erge
nts,
str
ong
Sal
ine
solu
tions
Hal
ogen
, dry
EC
alip
hatic
EC
chl
orin
ated
0 resistant 7 resistant with reservation 1 inconstant
Mat
eria
l
abb
revi
atio
n
Waterabsorption, %ASTM D 570
PE-HD 0 0 0 7 7 0 0 7 7 0 0 1 1 < 0,01
PE-LD 7 7 7 1 0 1 1 7 7 1 1 < 0,01
PP 0 7 7 1 0 0 7 7 7 0 0 1 1 0,01 à 0,03
POM 0 1 7 0 7 7 0 7 0 0 0 0 7 0,22 à 0,25
PA 6 0 0 0 0 7 0 7 0 0 0 1 7 7 1,3 à 1,9
Alc
ohol
Eth
er-s
alic
ylic
Cet
one
Eth
er
Ald
ehyd
es
Am
ines
Org
anic
aci
ds
EC
aro
mat
ic
Fue
ls
Min
eral
oils
Gre
ases
, oils
EC
chl
orin
ated
, non
-sat
urat
ed
Tur
pent
ine
Mat
eria
l
abb
revi
atio
n
Chemical resistance
Abbreviation/significancePE-HD High density polyethylenePE-LD Low density polyethylenePP PolypropylenePOM Polymethylene, polyacetatePA 6 Polyamide
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Plating andsurface treatments
Electrolytic processes
Relevant standards:– ISO 4042, Fasteners - Electroplated coatings
Zinc-plating – chromatingZinc-plating with subsequent chromating has proven to be veryeffective for fasteners with regard both to corrosion resistanceand appearance. We can offer you a comprehensive and well-stocked range. Our galvanised parts are shown in the catalogueshaded in grey/green.
Chromating (passivation) is carried out immediately afterzinc plating by a brief immersion in chromic acid solutions. Thechromating process improves corrosion resistance and preventsthe tarnishing or discolouring of the zinc layer. The protectiveeffect of the chromate layer varies according to process group(see table!).
Finish processes for chromating of electro zinc-platings
olive chromatizing olive green to olive brown (rare)
black chromatizing blackish brownto black (decorative)
1) «bluish» is not a clearly defined colour – it may differ.
2) Mass-produced parts can be black chromated, but only at great expense. Because of the barrel process, the black chromate layerwill almost always rub off on the edges, cross recessed edges etc. and may expose the bright zinc layer underneath.
Code system for electroplated coatings see ISO 4042.
Hours 200
150
100
50
03 5 8 12
Coating thickness (µm)
Time before appearance of red rust withchromating:
yellow oliveblue black
colourless
Corrosion resistance(salt spray test according to DIN 50021 SS)
Hydrogen embrittlement – alternatives (ISO 4042)
In cases of parts
– with high strength or surface hardness– which have absorbed hydrogen and– are under tensile stress, bending stress
there is the risk of failure due to hydrogen embrittlement. Sinceabsorption of hydrogen is typical for electroplating a baking pro-cess after the coating process may be necessary.
Threaded fasteners made from steel, heat-treated to propertyclass 10.9 (hardness 320 HV and above), casehardened faste-ners and fasteners with captive washers made from hardenedsteel over 400 HV (e.g. washers) shall be baked after electro-plating, but before any chromating treatment.
Parts shall be baked as soon as possible, but at least within 4hours after electroplating.
However, complete elimination of hydrogen em-brittlement cannnot be guaranteed. If completefreedom from embrittlement is required, than adifferent coating method shall be used.
For parts affecting safety, therefore, alternative corrosionprotection or coating processes should be selected, e.g.inorganic zinc coating, mechanical zinc coating or the use ofstainless steels.
Fasteners of classes ≥ 10.9 (≥ HV320) are supplied from ourstock with an inorganic zinc coating or are mechanically zinccoated where technically possible.
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Plating andsurface treatmentsCoating thicknesses for parts with
external thread ISO 4042
If no particular plating thickness is specified, the minimum pla-ting thickness is applied. This is also considered the standardplating thickness.
In the case of parts with very long thread or small dimensions (≤ M4), an irregular coating thickness may occur due to the pro-cessing. This can cause assembly problems. Possible solution: Use of a chemical nickel plating or stainlesssteel screws A2 or A4.
External threads are normally fabricated intolerance zone 6g.
e and f tolerance are not common and require specialmethods of screw manufacture. Minimum quantities, longerdelivery periods and higher prices may make theseeconomically unviable. An alternative is to use parts madefrom stainless steel A2.
Internal threads have a thinner coating due to technical rea-sons. However, this has no significance in practical use be-cause when assembled these are protected by the coatingof the external thread of the screw.
Measuring points for plating thickness
Measuring point Measuring point Measuring point Measuring point Measuring point Measuring point
Tolerance position g Tolerance position f Tolerance position eNominal Funda- Nominal coating thickness Funda- Nominal coating thickness Funda- Nominal coating thickness
Process DetailsNickel-plating Nickel-plating is decorative and provides effective corrosion protection. A hard coating, used in the electrical appliance and
telecommunications industries. No coating abrasion occurs, especially with screws. Improves protection against impregnation -see table below.
Veralisation A special method of hard nickel-plating.Chromium-plating Usually following nickel-plating. Coating thickness about 0,4 µm. Chromium is decorative,
enhances resistance to tarnishing and improves corrosion protection. Bright chromium-plated: high brightness finish.Matt chromium-plated: matt lustre (silk finish)Polished chromium-plated: grinding, brushing and polishing of the surfaceprior to coating electrolytically (done by hand).Drum chromium plating not possible.
Brass-plating Brass plating is mainly applied for decorative purposes. In addition, steel components arebrass-plated in order to improve the adhesion of rubber to steel.
Copper-plating Used when necessary as intermediate coating prior to nickel-plating-chromium-plating andsilver-plating. Used for decorative purposes.
Silver-plating Silver-plating is employed for decorative and technical applications.Tin-plating Tin-plating is carried out mainly to permit or improve soldering (soft-solder). Simultaneously
serves as corrosion protection. Subsequent heat treatment not possible.Anodizing When aluminum is anodized (electrolytic oxidation), a coating which provides corrosion
protection is produced – also prevents tarnishing. Practically any color can be produced fordecorative purposes.
Process DetailsHot-dip Immersion in molten zinc with a temp. of about 440 °C to 470 °C. Thickness of coating not less thangalvanising 40 µm. Finish dull and rough. Colour change possible after a certain time.
Very good corrosion protection. Can be used for thread parts from M8. Ensure good screwing nation by appropriate measures(by removal of chips before or after)
Phosphating Only slight corrosion protection. Good undercoat for painting. Grey to grey-black appearance.(bonderizing, Better corrosion protection oiled.parkerizing, atramentizingBlack Chemical process, bath temperature about 140 °C. For decorative purposes; merely slight oxidizing corrosion proteciton.Colouring According to sample.Blacking Chemical process. Corrosion resistance from A1-A4 may be low. For decorative purposes.Stainless steelBaking Following electrolytic or pickling treatment, high tensile strength steel parts (from 1000 N/mm2) can become brittle due to
hydrogen absorption (hydrogen embrittlement) This embrittlement increases for components with small cross sections.Part of the hydrogen can be eliminated by baking between 180 °C and 230 °C (below tempering temperature).Experience indicates that this is not guaranteed 100 %. Thermal treatment must be carried out immediately after plating andbefore chromating.
Dacromet An excellent process for zinc plating with a high percentage zinc coating (silver-grey colour) for parts with tensile strength(non-electroltytic) Rm ≥ 1000 N/mm2 (strength class ≥ 10.9, hardness ≥ 300 HV.
This process practically rules out hydrogen embrittlement. Temperatures resistant up to ca. 300 °C.Can be used for diameters ≥ M4
Mechanical plating Mechanical /chemical process. The degreased parts are placed in a drum with powdered zinc and glass pellets. The pelletsserve to transfer the zinc powder to the surface to be treated.
Impregnation Particularly with nickel-plated parts, subsequent treatement in dewatering fluid with the addition of wax may seal the micropores with wax. Significantly improves the corrosion resistance. The wax film is dry and invisible.
Further surface treatments
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Selection of fasteners
Estimation of screw diametersaccording to VDI guideline 22301)
FA
FA
FA
FA
FA
FA
FA
FA
FQ
FQ
1) Association of German Engineers
1 2 3 4Force Nominal diameterin N in mm
Strength class12.9 10.9 8.8
250400630
1 0001 600 M 3 M 3 M 32 500 M 3 M 3 M 44 000 M 4 M 4 M 56 300 M 4 M 5 M 5
10 000 M 5 M 6 M 816 000 M 6 M 8 M 825 000 M 8 M 10 M 1040 000 M 10 M 12 M 1463 000 M 12 M 14 M 16
100 000 M 16 M 16 M 20160 000 M 20 M 20 M 30250 000 M 24 M 27 M 36400 000 M 30 M 36630 000 M 36
or
1 step for either dynamic and centrical or static and eccentricforce
A Select in column 1 the next higher force to the work force FA
acting on the bolted joint.B The required minimum preload FMminis found by proceeding
from this number.4 steps for static or dynamic transverse (shear) force (seeexample)
Example:A joint is loaded dynamically and eccentrically by the axial forceFA = 8500N2). The screw of strength class 12.9 will be assem-bled with a manual torque wrench.
A 10'000 N is the next higher force to FA in column 1.
B 2 steps for «eccentric and dynamic axial force» lead to Fmin = 25'000 N.
C 1 step for «tightening» with manual torque wrench leads to FMmax = 40'000 N.
D for FMmax = 40'000 N thread size M10 is found in column 2.(Strength class 12.9.)
It is recommended to double check the result afterwardsby either calculating or testing the joint.
In order to assure a safely fastened joint, a number of parame-ters must be considered. For instance:
– Operating force (Direction of force, static or dynamic force)– Material being clamped (Surface pressure limit)– Operating temperature– Corrosion– Amount of friction 1)
– Inaccuracy of tightening methodetc.
The following procedure enables an estimation of screw diame-ters, taking the most important parameters into account. For theestimation an operating temperature of 20°C (68°F) is assu-med.
or
2 steps for dynamic, eccentric axial force
C The required maximum preload force FMmax is found by pro-ceeding from this force FM min by
2 steps for tightening the screw with a motorized/pneumaticscrewdriver which is set for a certain tightening torqueor
1 step for tightening with a torque wrench/or precision moto-rized screw-driver, which is set and checked by means of dy-namic torque measurement or elongation measurement ofthe screwor
0 step for «turn of the nut» method or yield point controlledmethod.
D Once the preload (force) has been estimated, the correctscrew size is found next to it in column 2 to 4 underneath theappropriate strength class.
or
0 step for static, centrical axial force.
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Fatigue resistanceStrength under dynamic loadaccording to VDI 2230
Because of their thread, screws are notched components.Under variable loads screws may be subject to fatigue fracture,which in 90% of cases this occurs in the first supporting threadat the entry of the female thread.In such cases the design of the screw must take into accountthe fatigue resistance ± σA ; this being only ±50 to 70 N/mm2 forscrews of property classes 8.8, 10.9 and 12.9, regardless of their sta-tic tensile strength which is much higher.
Fatigue fractures may occur under varying axial, bending ortorsion stresses. The design and controlled tightening must pre-vent or minimize these types of stress by using: elastic faste-ners rather than rigid ones, long screws rather than short ones,screws with reduced shanks, pins or shoulder screws to acco-modate lateral forces, and sufficient and specially controlledtightened screws. With bolts with reduced shanks the nut threadshould overlap the screw thread:
Constructions which are too weak must bestiffened. If the load allows, 8.8 screwsshould be used instead of 12.9 screws.
In the event of damage, the rupture pictureof the screws in relation to the machinebody must be analysed closely, i.e. brokenscrews must not be removed until after aprecise analysis!
Surface pressureReference values for Surface pressure limit for commonly used materialsaccording to VDI 2230
Material of Tensile Max. surfaceparts being clamped strength pressure limit3)
Surface pressure underneath head ofsocket head cap screws DIN 912 (ISO 4762)
1) The values for surface pressure which are shown in the tables are obtained with 90% utilization of the screw yield point Rp 0,2.
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Friction andcoefficientsof friction
The friction values µtotal, µG, and µK show great variation because they depend on many factors, such as the material pairing, thesurface quality (peak-to-valley heights); the surface treatment (bright. phosphated, blackened, electroplated, Dacromet-coated etc.)and the type of lubrication (with or without oil, molybdenum, di-sulphide, "Molykote" paste etc.)! The following tables show coefficientsof friction for threads and contact surfaces.
Coefficients of friction for standard finish of bolted joints
Coefficients of friction µ total of stainless steelscrews according to VDI 2230
The dispersion of the coefficients of friction remains high even when lubricants are used!
Smooth, rolled threads have less tendency to seize than do rough, cut threads. The frictioncoefficients µtotal assume an equivalent friction value in the thread and the head of the screwand under the nut.
1) For tightening with impact or mechanical screwdriver. µtotal, must be 0,125. For the other surface and lubricating conditions, areduction of µtotal at high assembly speed is probable, though not yet proven.
Surface condition µtotal for lubrication conditionScrew Nut oiled Mo S2-paste
– no subsequent treatment – no subsequent treatment– phosphated– electroplated approx. 8 µm – no subsequent treatment
(1)* ±5 to ±12 Yield Point controlled The fluctuation of the preload is primarily motorized tightening governed by the fluctuation of the yield load in the
(1)* ±5 to ±12 Angle of rotation (turn-of- Experimental determina– screw to be assembled. In this case, the screws are nut) controlled motorized tion of the snug torque designed for min. preload; thus, the tightening factor αA or manual tightening (pre tightening) and is omitted for this tightening method.
rotation angle (steps)1,2 – 1,6 ± 9 to ± 23 Hydraulic Tightening Setting is established by Low values for the long screws
measuring length High values for the short screwselongation or appliedpressure, respectively
1,4 – 1,6 ±17 to ±23 Torque control tightening Experimental determina- Lower values for:with manual torque tion of the nominal tighte- a large number of torquing testswrench or precision ning torque required on (e.g. 20) Lower values for:screwdriver with dynamic original screw, e.g. by Minimal fluctuations of the – small turning angles that is,torque control. elongation measurements output torque. relatively stiff joints
of screw. Electronically controlled torque – joint members with smoothduring assembly using precision surfaces (threads & bearingdrivers surfaces)
1,6 – 1,8 ±23 to ±28 Determination of required – surfaces that do not tend totorque by estimating the Lower values for: gall i.e. phospatedfriction coefficient. precision torque wrenches(surface and lubricating (e.g. with dial indicator) Higher values for:conditions) – consistent tightening – large turning angles that is,
– precision screwdrivers relatively flexible joints asHigher values for: well as fine threadstorque wrenches with acoustic – joint members with rough/signaling or release mechanism. hard surfaces
1,7 – 2,5 ±26 to ±43 Torque control tightening Pre-setting of power driver Lower values for: – form distortions (head to with precision power with post tightening torque, – a large number of torquing shank not perpendicular,screwdriver. which is established from tests and post torquing thread distortions)
the required torque (for – screwdrivers with cut-offestimated friction condi- couplingtions) plus post torquing.
2,5 – 4 ±43 to ±60 Impulse controlled tigh- Pre-setting of power Lower values for:tening with impact wrench. driver with post torquing – – a large number of torquing
as above tests (with post torquing)– on the horizontal axis of the
screw characteristics– play-free impulse
transmission
* Although αA is greater than 1, for the dimensioning equation αA is set at 1.
Tightening methodguidelinestightening factors αA
Guidelines for the tightening factorsand tolerances of the varioustightening methods tightening factorper VDI 2230
The tightening factor αA is the characteristic value for the app-lied tightening method.
maximum possible preload FV max. MA max.αA = minimum necessary preload FV min. MA min.
In order to guarantee the necessary preload FA in a joint, the mi-nimum needed screw dimensions are to be calculated. Then,the screws are to be tightened with a driver to the minimumneeded tightening torque. Different tightening methods involvedifferent tolerances (fluctuations). The less accurate the me-thod, the higher the tightening factor, the higher the tighteningtorque.Higher tightening torques require larger screw diameters towithstand the higher preloads.
Tightening methods with αA = 1, are considerable and expensi-ve and only justifiable for extremely critical applications.
~=
%
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Example: Maximum preload of an M6 cl. 8.8w/friction coefficient 0.125 = 9290 N(see preload section, 5th column)
With a total scatter of ±17%, the minimum torque =
8.46 x 0.83 = 7.02 Nm
mean torque min. torque
The minimum preload is then calculated as follows:
9290 ÷ 9.9 x 7.02 = 6587 N
max. preload max. torque min. torque minimum preload
Torque chartHow to use the torque chart
Is the minimum preload adequate (preven-ting slipping or separating of joint members)?If not, use a bigger screw diameter with thesame property class (Repeat step 3 to 5)
or
choose a screw with a higher property class.
Caution: Higher strength bolts cause highersurface pressure underneath head / nut (seetable page T.031
Step 5: Check preload
Step 4: Deduct scatter (tolerance) of tightening method(when tightened with a commercial torque wrench a tolerance of ±17 to ±23% can be taken into consideration.)1)
Mean torque if scatter is ±17% > 9.9 ÷ 1.17 = 8.46
Torque to be set on torque wrench = 8.46 Nm
Step 2: When the surface condition (finish) is defined, the friction coefficient can be found in the small chart below the torque chart:
Step 1: One has to know whether the screws to be tightened are:• plain• zinc plated• cadmium plated• Mo S2 lubricated («Moly lub» lubricated) etc.
Step 3: The proper tightening (seating) torque can then be obtained from the torque tightening chart.
Example: Zinc plated = 0.125
Example: Hex cap screw DIN 933 property class 8.8 zinc plated M6 x 20 dry
Then, look for the thread size M6 (left hand side of chart)Choose friction coefficient (2nd column)Move over to the right to tightening torque chart (5th column)The maximum torque is 9.9 Nm
Step 6 To get the torque in «Inch/pound units» the following factors can be used:
To get inch pounds from Ncm x 0.08851To get foot pounds from Ncm x 0.00737To get foot pounds from Nm x 0.7376
Example: 8.46 x 0.7376 = 6.24 foot pound
Notes:1) Any tightening method involves certain inaccuracies which are the result of: – Estimating the friction coefficient
– Manipulation errors of torque wrench (operator errors)– Tolerance of torque wrench itself etc.
Depending on how much these factors can be measured and / or controlled in the in-house assembly or field assembly, either a higher or lower scatter must be considered. (see T.033)
Note: To make sure the applied torque does not inducea preload, exceeding 90% of the yield strength, the scat-ter must be considered. To allow for the scatter, the mean torque must be calculated.The torque to be set on the torque wrench is the calculatedmean torque. With this setting with maximum scatter, 90% ofthe yield strength would not be exceeded.1)
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Preload andtightening torques
Metric coarse threadMaximum permissible preload and tightening torques forscrews of property classes 3.6–12.9 at 90% utilization of theyield point ReL or Rp0,2
Maximum preload Fv [N] Maximum tightening torque MA [Ncm]
Property class according to ISO 898 / 1 Property class according to ISO 898 / 15.6 5.6
1) The mechanical characteristics and property classes according to ISO 898, part 5 are valid for headless screws not subjected to tensile forces.
Fasteners made from these steels tend to erode during fitting. Thisrisk can be reduced through smooth, clean thread sufaces (rolledthreads), lubricants, molykote smooth varnish coating (black), lownumber of revolutions of the screwdriver, or continuous tightening wi-thout interruption (impact screwdriver not recommended). For coeffi-cients of friction, see T.032.
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Preload andtightening torquesLocking screws and nuts,
flange screws and nuts (according to manufacturer's specifications)
according to DIN 6914(HV sets according to DIN 6914 / 15 / 16)
Dimensioning, design and manufacture of fasteners with high-strength structural steel bolts are regulated in DIN 18800,parts 1.
The strength of high-strength structural steel bolts correspondsto the value stipulated in DIN 267, respectively ISO 898:
– ISO 898, part 1 for bolts DIN 6914
– DIN 267, part 4 for nuts DIN 6915
– Washers DIN 6916, 6917, 6918 of steel hardened to 295-350HV 10
1 2 3 4 5 6 7 8 9Screw prestressed according to the
Torque procedure Impact Angle of rotation procedureprocedure
Screw Required Tightening torque MA Preload Pre-tightening Clamping Angle of rotation ordiameter preload FV to be applied to be torque to length number of revolutions
in the screw lubricated with lightly applied be applied MoS2 1) oiled FV
2) MA2) lk
3) ϕ 2) U2)
mm kN Nm Nm kN Nm mm1 M 12 50 100 120 60 102 M 16 100 250 350 1103 M 20 160 450 600 1754 M 22 190 650 900 2105 M 24 220 800 1100 2406 M 27 290 1250 1650 3207 M 30 350 1650 2200 390 2008 M 36 510 2800 3800 5609 M 12 see 0 to 50 180° 1/2
10 to lines 51 to 100 240° 2/311 M 36 1–8 101 to 240 270° 3/4
1) Since the values MA are highly dependent upon the thread lubricant, observance of these values must be confirmed by the screw manufacturer.2) Does not depend on the lubrication of the thread and the contact surfaces of nut and screw.3) For screws M12 to M22 with clamping lengths 171 to 240 mm, an angle of rotation ϕ 360° and U = 1 must be used.
To apply a partial preload force ≥ 0,5 · FV, half the values of columns 3 to 5 and 8 or 9 and hand-tightening according tocolumn 6 is sufficient.
The following methods are available for applying preload to thebolt:
– with hand operated torque wrench (torque process)
– with power screwdriver which must be regulated to a well de-fined torque (angular torque)
– angle of rotation process, in which after having applied a cer-tain preload, the nut or bolt is retightened with a well definedangel of rotation.
50
100
Table 1, which is taken from DIN 18800 part 7, shows the necessary preloads, torques and tightening angles. The screwsmay be tightened either by the nut or by the screw.
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Securely fastenedjointsSummary of constructive measures for
locking screw joints
In principle, there are two reasons why bolted connections may need locking:
Loosening due to setting Rotational loosening
d
FQ
FQl K
FV
FV
SG
fSM fpM
FZ
FM min.
FM
fZFA
FA
FV
FM = assembly preloadfSM = elongation of screw through FM
fPM = shortening of compressed parts through FM
FV = final preloadFZ = loss of preload due to setting fZ = amount of settingFA = operation forceFM min = FV + FZ
Locking agianst loosening due to setting Locking against rotational loosening
Measures Effect achieved Measures Effect achievedClean, smooth joint interfaces Reduction of setting possibilities Bigger screws. Lateral movement of theminimum number of interfaces Higher property classes joint members canNo soft, plastically deformable be prevented by a higher preloadjoint membersLong screws (l K > 4xd). High elasticity, compensation of preload loss Shoulder screws No possibility for screws with reduced shank Parallel or dowel pins lateral movementsspring washersFasteners with flange The larger bearing area reduces Long screws (L > 4xd). Flexible joint
the suface pressure. Screws with Better fatigue resistance.Larger tolerance for clearance holes reduced shank
Special large washers with Same advantages as above.hardness 200 HB For screws up to property class 10.9
Loosening of bolted joints results in preload loss. This loss iscaused by setting of the joint members or by a permanent elon-gation of the screw after tightening or under the operation forceFA.
Dynamic shear forces FQ acting upon the bolted joint can causethe joint members to slip back and forth. This will prompt screwsand nuts to rotate, this reducing the preload until it is zero.
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Securely fastenedjointsList of additional locking possibilities
against the loosening of the threaded jointand security against loss.
Caution!The safety qualities shown in the following table relating toloosening, backing out and / or loss are based exclusively onfield experience.
It is the responsibility of the user to examine the differentelements and methods having regard to the specific case ofuse.
Security againstloosening due rotational
Item to setting loosening loss Commentsdiv. 5.8 8.8 10.9 div. 5.8 8.8 10.9
Cheese head screws, hexagon screws and nuts Increased loosening torque due to corrugated basewith corrugated flange (Verbus Ripp )Hexagon head screws and hexagon nuts with Serrated flange surface increases frictionserrated flange (Tensilock )Hex and pan washers Increased bearing area due to the large pan washerhead screws (eco-fix )ThreeBond, DELO, Precote Chemical thread locking adhesives eliminate
thread playScrews with polyamide patch on thread (Tuflok ) Locking against loss by thread friction,
max. 120 °CThread-forming screws for metals DIN 7500 Overall locking effect through a formed,
play-free threadThread-forming screws for thermoplastics (PT ) Overall locking effect through a formed,
play-free threadPrevailing torque nuts DIN 982/985 etc., Locking against loss because of polyamid locking
element on the thread max. 120 °CPrevailing torque nuts DIN 980 / ISO 7042 etc. Locking against loss because of a metallic
locking elementSeal nuts with clamping part (Seal-Lok ) etc. Locking against loss and sealing because of a
polyamid locking element, max. 120 °CElastic nuts (Serpress ) etc. Locking effect through elasticity
no prevailing torqueCastle nuts DIN 935 etc. Cotter pin prevents loss,
Limited loosening is possibleHex lock nuts with spring washer (Comby-S) Attached spring lock washer compensates for setting
Hex lock nuts with toothed lock washer Attached serrated lock washer increases friction(BN 1364)Spring washers DIN 127A / DIN 128A / Compensate settingDIN 7980 etc.Serrated and toothed lock washers Increase frictionDIN 6798 / 6797 etc.Ribbed lock washers BN 791 (Rip-Lock ) etc. Universal lock washer:
compensates setting, increases frictionConical spring washers SN 212745 / Heavy duty type (up to 8.8)DIN 6796 etc.Cotter pins DIN 94 etc. For castle nuts, expensive assembly
Locking effect:
very good
good
moderate
Technical information Thema B No. 1 gives comprehensive information securely fastened joints. Please ask for a copy!
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Shear loads for pins
Dowel pins (clamping sleeves)heavy finish according to ISO 8752 / DIN 1481
from 10 mm nominal diameter Material: spring steel hardened andtempered to 420 to 560 HV
Mt
single lap joint double lap joint
F
F F F
2F
Spiral pins, heavy finish according to ISO 8752 (DIN 1481)
Spiral pins, standard finish according to ISO 8750 / DIN 7343
Spiral pins, heavy finish according to ISO 8748 / DIN 7344
Dowel pins (clamping sleeves) light finishaccording to ISO 13337 / DIN 7346
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Constructionrecommendations
Thread forming screws per DIN 7500 produce a strong, chipfree mating thread into flowable materials (steel, HRB 135 max.,aluminum, brass, copper, etc.). Generally, thread formingscrews made of A2 stainless steel can only be driven into alumi-num.
Technical Data and Mechanical Properties
The tapered thread point does not carry any load, which shouldbe considered when determining the nominal screw length. Forharder materials, the hole size should be defined by means ofexperimentation.When used in aluminum, with an engagement depth of over1,5x the diameter, the hole diameter can be reduced by roughly 2%.
Thread forming screws for metalsaccording to DIN 7500
Thread pitch P mm 0,4 0,45 0,5 0,6 0,7 0,8 1 1,25Tightening torque max. approx. 80% of breaking torqueBreaking torque Nm 0,5 1 1,5 2,3 3,4 7,1 12 29Tensile force min. kN 1,7 2,7 4 5,4 7 11,4 16 29Material thickness s mm pilot hole diameter d – H11 for steel, HB max. 135; drilled or punched 2 and smaller 1,8 2,25 2,7 3,15 3,6 4,5 5,4 7,25 4 1,85 2,3 2,75 3,2 3,65 4,5 5,45 7,3 6 2,35 2,8 3,25 3,7 4,6 5,5 7,35 8 3,3 3,75 4,65 5,55 7,410 4,7 5,6 7,4512 5,65 7,514 7,516 7,55
Pilot holes and pilot hole geometry for die castingsBecause conditions may vary, it is suggested to carry out appli-cation oriented experiments to double check the given recom-mendations.
Further information (trumped-shaped punched holes etc.) can be obtained from our extensive productdocumentation. Ask for a copy!Our engineering department is prepared to provide technical advice. During the construction phase we can carryout field-related application tests in our laboratory.
d2
d3
d1 d1
t 1
t 3t 1
α α
t 2
A = max. 4 PB = possible bearing thread lengthC = total length, tolerance js 16s = thickness of material
blind hole through hole
α = max. 1°
(t1 + t2 - 1) (t1 + t3 + 4P)
Generalt1 mm: top part of the pilot hole, with significant taper which has benefits for the casting of radii,
strengthening of the mandrel, centering of the screw, prevention of material back-up and
adaptation to standardised and less coastly screw lengths.
t2 / t3 mm: bearing part of the pilot hole, max. taper angle 1°
Screw penetration:
Nominal thread diameter M2,5 M3 M3,5 M4 M5 M6 M8dH12 mm 2.7 3,2 3,7 4,3 5,3 6,4 8,4d1 1) mm 2,36 2,86 3,32 3,78 4,77 5,69 7,63d2 1) mm 2,2 2,67 3,11 3,54 4,5 5,37 7,24d3 1) mm 2,27 2,76 3,23 3,64 4,6 5,48 7,351) + mm 0 0 0 0 0 0 0for d1, d2, d3 – mm 0,06 0,06 0,075 0,075 0,075 0,075 0,09t1 mm variable, minimum 1 x thread pitch Pt2 2) mm 5,3 6 6,9 7,8 9,2 11 142) + mm 0,2 0,2 0,6 0,5 0,5 0,5 0,5for t2 – mm 0 0 0 0 0 0 0t3 mm 2,5 3 3,5 4 5 6 8
Direct assembly of thermoplasticparts with eco-syn screws
Eco-syn screws offer great advantages:
0 low driving torque, high stripping torque0 high breaking torque0 excellent security against vibration0 low risk for cracking the base material0 no setting of the assembly due to excessive
relaxation of the plastic material
The head of the eco-syn screw already conforms in shape anddimensions to international ISO standards and therefore also toEuropean standards derived from them:
Raised cheese head ISO 7049 Countersunk head ISO 7050
0 lower fadial forces 0 more plastic material between the points 0 no global deformation and only localizedof the thread stressing of the thermoplastic material
0 larger depth of thread engagement 0 increased shear surface 0 Easy peretration of the thread into theplastic material
0 less pressure of the flanks on the plastic 0 high resistance to stripping 0 no microcracks produced due to excessivematerial stress in the plastic material
0 improved security against possible strippingof the plastic counter-thread
FeFB
tB
60°
te
30°
FA
FRB
60°
FA
FPB
®
FPeFRe
FA
FA
30°
30°
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Assembly and application guidelines for the eco-syn screw
The recommended pilot hole diameters, as well as the engage-ment length are provided for guidance. Because conditions of-ten vary, the user of eco-syn screws should make his own testson prototypes or similar parts to determine whether it fits theparticular use.Pilot hole diameters and engagement lengths should be definedin a manner, so that the plastic is not strained excessively.
The relief counterbore is significant, since it eases the locatingof the hole during assembly. Additionally, it enables a more fa-vorable stress distribution around the margin area.
Material Hole Ø Outside Ø Engagementlenght min.
ABS / PC blend 0,80 x d 2,00 x d 2,00 x dASA 0,78 x d 2,00 x d 2,00 x dPA 4.6 0,73 x d 1,85 x d 1,80 x dPA 4.6 - GF 30 0,78 x d 1,85 x d 1,80 x dPA 6 0,75 x d 1,85 x d 1,70 x dPA 6 - GF 30 0,80 x d 2,00 x d 1,90 x dPA 6.6 0,75 x d 1,85 x d 1,70 x dPA 6.6 - GF 30 0,82 x d 2,00 x d 1,80 x dPBT 0,75 x d 1,85 x d 1,70 x dPBT - GF 30 0,80 x d 1,80 x d 1,70 x dPC 0,85 x d 2,50 x d 2,20 x d1)
PC -GF 30 0,85 x d 2,20 x d 2,00 x d1)
PE (soft) 0,70 x d 2,00 x d 2,00 x dPE (hard) 0,75 x d 1,80 x d 1,80 x dPET 0,75 x d 1,85 x d 1,70 x dPET - GF 30 0,80 x d 1,80 x d 1,70 x dPMMA 0,85 x d 2,00 x d 2,00 x dPOM 0,75 x d 1,95 x d 2,00 x dPP 0,70 x d 2,00 x d 2,00 x dPP - TV 20 0,72 x d 2,00 x d 2,00 x dPPO 0,85 x d 2,50 x d 2,20 x d1)
PS 0,80 x d 2,00 x d 2,00 x dPVC (hard) 0,80 x d 2,00 x d 2,00 x dSAN 0,77 x d 2,00 x d 1,90 x d
d = nominal Ø of screw
1) These plastics are sensitive to stress cracking, thereforeageing tests as recommended by the material manufacturershould be conducted. For these plastics it is particularly im-portant that the relief counterbore is produced exactly asshown.
external Ød
0.3–
0.5
d
s
te
pilot hole Ø
Recommendation for injection moulding
If necessary:
– reduce the external tube diameter DT– increase pilot hole diameter dL
– increase pilot hole depth and thus the penetration of the screw depth in order to compensate for reduced strip resistance.
Choose pilot holes which are deep enough for the assembledscrew not to contact the bottom of the hole.
Our engineering department is prepared to provide technicaladvice. Even in the construction phase we can carry out field-related assembly tests for you in our laboratory for applicationtechnique.
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ConstructionrecommendationsSheet metal joints
(use) according to DIN 7975
The informtion below represents general recommendations forthe use of screws for sheet metal joints. The different types areshown by way of example.
Minimum total thickness of the sheet metals to befastened
The total thickness of the fastened parts shall be bigger than thethread pitch of the applied tapping screw; or else, because ofthe thread run out underneath the head, a sufficient tighteningtorque can not be applied. Should this be the case, joints suchas shown in figure 3 to 6 should be applied.
Fig. 1: Simple fastening(two core holes)
Fig. 2: Simple fasteningwith clearance hole
Fig. 3: Pierced core hole(thin sheet metal)
Fig. 4: Extruded core hole(thin sheet metal)
Fig. 5: Pressed hole fastening joint
Fig. 6: Fastening with spring nut
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Constructionrecommendations
Sheet metal joints(utilisation) according to DIN 7975
The following reference values are valid only for case hardened steel self-tapping screws as shown in Figure 2 on page T.046. Thetightening torques are max. 50% of the minimum breaking torque. Prior tests must be carried for the utilisation of other screws or ot-her sheet metal materials. Punched pilot holes must be 0,1–0,3 mm larger.The screws must be tightened in the direction the hole was punched.
Self-tapping screws / sheet metal thicknesses / pilot hole diameters
Thread Material Diameter of the pilot hole for db thread dimensions ST 2,2 à ST 6,3diameter strength for a sheet metal thickness s [mm]
The recommended hole diameter depends on the Ensat
external thread, the strength and the physical characteri-stics of the workpiece material.Hard and brittle materials require a larger hole than softand flexible ones. Whenever necessary, the most suita-ble hole diameter should be determined by trial.
Ensat For material groupstype I II III307/308 Attainable percentage of overlapping337/338 threads
For hard and brittleplastics.DA = D + 0,2 to 0,4t = pilot hole depth
For metallicmaterialsa = 1 to 1,5 x pitch ofexternal thread
Recommended pilot hole diameters
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Constructionrecommendations
Internal drives for screws
– Technical progress and economic factors have resulted in the increasing replacement of slotted head screws by other internaldrive systems.
– It is very important today to take into account the most frequently used drives and their possibilities in design, logistics,procurement and assembly.
– The Phillips cross recessed head is the world's most widely used system.
– Has a conventional cruciform recess with all walls inclined, the end of the screwdriver having trapezoid webs.
– The general dimensions are given in the product information in the catalogue.
– The Pozidriv cross recessed head is used principally in Europe.
– The four «tightening walls» of the cruciforme recess in contact with the screwdriver when tightening, are perpendicular. The other walls are inclined. This can improve assembly if therecess production is reliable. The Pozidriv screwdriver hasrectangular webs at its extremity.
– The general dimensions are given in the product informationin the catalogue.
– Screws with hexagon socket head have proved their worth in the machine and apparatus construction fields.
– The width across flats of hexagon socket head screws is smaller than the WAF of hexagon head screws, permitting more economic design with smaller sizes.
– The general dimensions are given in the product information in the catalogue.
– The notion of a drive with hexalobular sockets are a decisive step in developing drives betteradapted to manual and automated assembly. This drive is becoming increasingly popular throughout the world.
– Compared to drives like cross recesses and conventional hexagon sockets, this system is characerised by a lower risk of deterioration and a lower pressure force requirement. The typical «cam out» slipping of the tool has hence been eliminated and the force transmission improved.
– The general dimensions are given in the product information in the catalogue.
Cross recess H (Phillips) according to ISO 4757
Cross recess Z (Pozidriv) according to ISO 4757
Hexagon socket
Hexalobular socket according to ISO 106641) (Torx )
1) Draft
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S
Constructionrecommendation
Internal drives for screws
No deterioration of the internal drive; hence reliable un-screwing. Very low assembly tool wear.
High rationalisation potential for the assembly technique,as the drive is suitable for all types of screw.
Economic head from the aspect of size, form and materi-al, corresponding to cheese head screws DIN 84 andDIN 7984, however able to cope with high stresses withrespect to permissible surface pressure.
No problem assembling round head screws according toISO 7380 and recessed flat head screws DIN 7991. Thehigh property class 10.9 of these screws permitting incre-ased strength of the hexagon socket can be reduced toproperty class 8.8.
– The Torx plus drive is defined by ellipses and represents an improvement over the original hexalobular system which is defined by a series of radii.
– The Torx plus system is compatible with the tools provided for the(Torx ) hexalobular system.However, the specific geometric benefits of Torx plus can only optimise assemblywhen using the Torx plus screwdriver bits (tool).
– The general dimensions are given in the product designations in the catalogue.
Torx plus
Technical advantages of hexalobular socket and Torx plus drives
The hexalobular socket and the Torx plus systems have benefits due to their design parameters
– The effective transmission angle of the hexalobular socket is 15° and that of the Torx plus is 0°. The force applied is that actually used for tightening the screw. The geometries of the hexalobular socket and the Torx plus therefore extend the service life of the screwdriver bits by up to 100%.
– The cross section of the Torx plus drive is larger compared to the hexalobular system. Therefore the torsional strength of the driving tool is increased.
– The good force transmission enables low penetration depths.
No need for pressure force as is necessarywhen using cross recessed drives.
Can accept the tightening torques for all pro-perty classes.
Force transmission angle of 60°with hexagon socket drives
0°
Force transmission angle of 0°with Torx plus drives
Force transmission angle of 15°with hexalobular socket drives
15°60°
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Metric ISO threads
General
The thread dimensions and profile accuracy are crucial for de-termining:
0 whether a coating can still be applied to the screw thread.0 whether the parts to be joined can be screwed together on
assembly without difficulty or the need for reworking.
0 whether the thread can transmit the forces for which the components were dimensioned.
0 Tolerances are very small in screw manufacturing. Terms and fitting systems are difficult to understand. To assist. the following illustrations explain dimensions and tolerances.
Basic concept and nominal dimensions according to ISO 724
The dimension system for threads is based on the nominaldimensions for thread, pitch and minor diameter. 60°Nut
D n
omin
al s
ize o
f thr
ead
D m
ajor
dia
met
er
D 2 p
itch
diam
eter
D 1 m
inor
dia
met
er
d 2 p
itch
diam
eter
d m
ajor
dia
met
er
Nut Bolt
Bolt
P pitch
Clearance fit on metric ISO threads according to ISO 965
Screw and nut threads have different tolerance zone positions:screw thread dimensions are situated at the nominal dimensionand below, nut thread dimensions, at the nominal dimensionand above.This produces the necessary clearance and a defined range forpermissible plating thicknesses: a plated screw thread mustnever exceed the nominal dimensions, while a plated nut threadmust never fall below them (see T.027).
Td 2
Td2 2TD
1 2
El2
es2
maj
or d
iam
eter
min
.
pitc
h di
amet
er m
ax.
pitc
h di
amet
er m
in.
min
or d
iam
eter
max
.
min
or d
iam
eter
min
.
pitc
h di
amet
er m
in.
pitc
h di
amet
er m
ax.
maj
or d
iam
eter
min
.
maj
or d
iam
eter
max
.
Nut
Bolt
TD2 2
maj
or d
iam
eter
max
.
Tolerance fields for commercialscrews and nutsaccording to ISO 965
The ISO 965 thread standard recommends tolerance fieldswhich give the desired clearance. For threads ≥ M1,4, thefollowing tolerance fields are standard!
6H 6G
6g 6e
Ø m
ajor
Ø pi
tch
Ø m
inor
Ø m
ajor
Ø pi
tch
Ø m
inor
Larger numbermeans greatertolerance
4 5 6 7 8
TOLERANCE QUALITYDiameter-dependenttolerances for differenttolerance qualitiescan be found in ISO 965.
TOLERANCE ZONE POSITIONPitch-dependent dimensionsfor different tolerancezone positions can be foundin ISO 965.
CLEARANCEBEFOREAPPLICATIONOF PROTECTIVECOATS
GO – H – h
gfe
bolt
thre
ad
nut t
hrea
d
Nut Bolt Surface condition6H 6g bright. phosphated or for standard
electroplatings6G 6e bright (with large clearance) or for
very thick electroplatings
6g-ring ganges for plain screw threads6h-ring ganges for plated screws Tolerance fields of screw and nut threads
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Metric ISO threads
Limits for metric (standard) coarse threadsaccording to ISO 965
Bolts, tolerance 6g (*6h)
Nominal diameter Pitch
series 1 series 2 P 1 0,25 1,2 0,25
1,4 0,3 1,6 0,35
1,8 0,35 2 0,4 2,5 0,45 3 0,5
3,5 0,6 4 0,7 5 0,8 6 1
7 1 8 1,2510 1,512 1,75
14 216 2
18 2,520 2,5
22 2,524 3
27 330 3,5
33 3,536 4
39 4421) 4,5
451) 4,5481) 5
521) 5
Nuts, tolerance 6H (*5H)
Selectionseries for standard threads ISO 262
1) Not contained inISO 262–1973
Thread Length of thread Major diameter Pitch diameter Threadengagement d mm d2 mm root radius
Dimensions of the head, screw length andthread approximate according to DIN. Acceptance according to VDI 2544.
The tolerances must be observed 24 hoursafter fabrication, for all other tolerances,refer to ISO 4759, part 1, but withthe factor 2.
These technical recommendationsare of a general nature. For moredetailed specifications, please re-fer to VDI 2544.
Dimension for screw threads for nut threadsmajor Ø e8 2 x G7minor Ø 2xg8 H7pitch Ø 2xg8pitch ± 5%
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1) The fastener sizes in preference class 1 are suggested to be used in all designs. The sizes in this category are generally, readily available.
2) Fasteners in preference class 2 should be chosen only if a size in preference class 1 is not feasible. For preference class 2 sizes, longer lead times have to be expected.
3) Preference class 3 sizes are not recommended for fasteners (normally used for shaft ends etc.)4) Note: Use metric drill sizes whenever possible. The listed US-drill sizes are as close as they possibly can be. Nevertheless,
they may not be adequate in all circumstances.5) No fractional size is close enough.6) Coarse = standard metric thread
Preference class Pitch Drill Closest Drill Closest Clear- Closestsize for recommended size for recommended ance recommended
11) 22) 32) tapping US tapping US hole UScoarse6) fine M coarse size4 M fine size4 size4
Metric threadsPreference classes / diameter-pitch combination / metric tap drill size and clearance holes (US-drill sizes for reference4))
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Nominal dimensions
Nominal dimensions on Metric Fasteners
L
d 1
L
d 1
L
d 1
L
d 1
L
d 1
L
dd s
Nominal dimensions of Metric FastenersStandard fasteners are defined by: Nominal thread diameter (d) x nominal length . Ex. M8 x 45
Nominal dimensions on shoulder screws
Shoulder screws are defined by: Shoulder diameter and shoulder length
In order to avoid incorrect shipments, it is recommended to indicate the thread diameter as well.
Therefore indicate the following: – shoulder diameter [ds]– shoulder length [L]– thread diameter in parenthesis [d]
Example: ds x L (d) = 6 x 20 (M5)
Determination of nominal dimensions on studs (DIN 939, 938, 835)
L
d 1
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ISO-Tolerances
Tolerances for Metric Fasteners.
The tolerances in the tables shown below are derived from ISO4759: Tolerances for Fasteners Product grades A and B 1.)
The tolerances listed apply for the most common types of metricfasteners. Approximately 98% of the fasteners stocked by Bos-sard are in accordance with DIN and ISO specifications. Other national metric fastener standards derive tolerances from
ISO 4759. However, occasionally some slight modifications aremade.
The tolerances are indicated by tolerance zones. The actual tol-erances in millimeters are then found from the tolerance chart.
For tolerances on fasteners not shown in this table consult:
ISO 4759 or DIN 267 Part 2.
Item DIN ISO Item DIN ISO Item DIN ISOProduct grade: A1)
963 2009 912 4762 931 4014965 7046 960 8765
≤ 5 = h 13 > 5 = h 14Product grade: A1)
84 1207 7991 933 4017961 8676
≤ M5 : h13 / > M5 : h14Product grade: B1)
913 402685 1580 914 4027 931 4014
916 4029 960 8765
≤ M5 : h13 / > M5 : h14Product grade: B1)
964 2010 915 4028 933 4017966 7047 961 8676
439 4035934
7985 7045 ≤ M 12 : h 14 936 4033> M 12 ≤ M 18 : h 15 970
> M 18 : h 16 971 40326330
≤ M5 : h13 / > M5 : h14
1) Product grade A applies to nominal thread diameters up to and including M 24 and lengths not exceeding 10 d or 150 mm,whichever is shorter.
Product grade B applies to sizes above M24 or lengths exceeding 10d or 150 mm, whichever is shorter.
2) js 16 for machine screws with L > 50 mm
js 15/16 2)
+2 P
h 13/14
h 14
h 13
js 15/16 2)
+2 P
h 13/14
h 14
h13
js 15/16 2)
+2 P
h 14
h 13
+ 2°
h13/14
+2 P
h 14
h 13
js 15/16 2)
h 13/14
h13
js 15
h 13
+2 P
+ IT 14
h 14
js 15
+2 P
+ 2°
h 13
js 15
h 14
js 15
+ IT 14
js 14 js 15
+2 P
js 15
h13
js 14 js 15
js 15 js 15
+2 P
js 16
h13
js 15 js 16
js 16
+2 P
h 14
h 13
+ 2°
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ISO-Tolerances
Tolerance zones for sockets, slots and width across the flats
Feature Feature
Hexagon sockets Product Slots*** Productgrade A grade A
Tolerance n Tole-s * ** rance*
0,7 EF8 ≤1 C130,9 JS91,3 K9 >1 C141,5 D9 D102
2,5 D10 D11 Widths across flats Product3 D11 Grade: A2
4 E11 s Tol.5 ≤32 h136 >32 h148 E11 Product
10 E12 Grade: B2
12 s Tol.14 ≤19 h14
>14 >19≤ 60 h15D12 >60≤180 h16
>180 h17
* Tolerance zones for socket set screwsNote: For s 0,7 to 1,3 the actual allowance in the product standards has been slightly modified for technical reasons.
** Tolerance zones for socket head cap screws
s
ee
s
nn
n
s s
ss
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Tables / tolerances /standardsBasic tolerances and tolerance fields
Extract from ISO 286-2
No
min
alS
tan
dar
d t
ole
ran
ces
To
lera
nce
fie
lds
for
dim
ensi
on
[mm
]E
xter
nal
dim
ensi
on
s [m
m]
Inte
rnal
dim
ensi
on
s [m
m]
ran
ge
IT11
IT12
IT13
IT14
IT15
IT16
IT17
b 1
3h
11
h12
h 1
3h
14
h 1
5h
16
h 1
7js
14
js 1
5js
16
js 1
7D
12
H 1
1H
12H
13H
140,
060,
10,
10,
250,
40,
61
1 )–0
,14
0
0 0
0 0
0–
±0,1
25±0
,2±0
,3±0
,51 )
+0,
12+
0,06
+0,
1+
0,14
+0,
25u
p t
o3
–0,2
8–0
,06
–0,1
–0,1
4–0
,25
–0,4
–0,6
+0,
02 0
0 0
0o
ver
30,
075
0,12
0,18
0,3
0,48
0,75
1,2
1 )–0
,14
0 0
0 0
0 0
–±0
,15
±0,2
4±0
,375
±0,6
+0,
15+
0,07
5+
0,12
+0,
18+
0,3
up
to
6–0
,32
–0,0
75–0
,12
–0,1
8–0
,3–0
,48
–0,7
5+
0,03
0 0
0 0
ove
r6
0,09
0,15
0,22
0,36
0,58
0,9
1,5
–0,1
5 0
0 0
0 0
0 0
±0,1
8±0
,29
±0,4
5±0
,75
+0,
19+
0,09
+0,
15+
0,22
+0,
36u
p t
o10
–0,3
7–0
,09
–0,1
5–0
,22
–0,3
6–0
,58
–0,9
–1,5
+0,
04 0
0 0
0o
ver
100,
110,
180,
270,
430,
71,
11,
8–0
,15
0 0
0 0
0 0
0±0
,215
±0,3
5±0
,55
±0,9
+0,
23+
0,11
+0,
18+
0,27
+0,
43u
p t
o18
–0,4
2–0
,11
–0,1
8–0
,27
–0,4
3–0
,7–1
,1–1
,8+
0,05
0 0
0 0
ove
r18
0,13
0,21
0,33
0,52
0,84
1,3
2,1
–0,1
6 0
0 0
0 0
0 0
±0,2
6±0
,42
±0,6
5±1
,05
+0,2
75+
0,13
+0,
21+
0,33
+0,
52u
p t
o30
–0,4
9–0
,13
–0,2
1–0
,33
–0,5
2–0
,84
–13
–2,1
+0,0
65 0
0 0
0o
ver
30–0
,17
up
to
40–0
,56
0 0
0 0
0 0
0+
0,33
+0,
16+
0,25
+0,
39+
0,62
ove
r40
0,16
0,25
0,39
0,62
11,
62,
5–0
,18
–0,1
6–0
,25
–0,3
9–0
,62
–1–1
,6–2
,5±0
,31
±0,5
±0,8
±1,2
5+
0,08
0 0
0 0
up
to
50–0
,57
ove
r50
0,19
0,3
0,46
0,74
1,2
1,9
3–
0 0
0 0
0 0
0±0
,37
±0,6
±0,9
5±1
,5+
0,4
+0,
19+
0,3
+,0
46+
0,74
up
to
80–0
,19
–0,3
–0,4
6–0
,74
–1,2
–1,9
–3+
0,1
0 0
0 0
ove
r80
0,22
0,35
0,54
0,87
1,4
2,2
3,5
– 0
0 0
0 0
0 0
±0,4
35±0
,7±1
,1±1
,75
+0,
47+
0,22
+0,
35+
0,54
+0,
87u
p t
o12
0–0
,22
–0,3
5–0
,54
–0,8
7–1
,4–2
,2–3
,5+
0,12
0 0
0 0
ove
r12
00,
250,
40,
631
1,6
2,5
4–
0 0
0 0
0 0
0±0
,5±0
,8±1
,25
±2+0
,545
+0,
25+
0,4
+0,
63+
1u
p t
o18
0–0
,25
–0,4
–0,6
3–1
–1,6
–2,5
–4+0
,145
0 0
0 0
ove
r18
00,
290,
460,
721,
151,
852,
94,
6–
0 0
0 0
0 0
0±0
,575
±0,9
25±1
,45
±2,3
+0,
63+
0,29
+0,
46+
0,72
+1,
15u
p t
o25
0–0
,29
–0,4
6–0
,72
–1,1
5–1
,85
–2,9
–4,6
+0,
17 0
0 0
0o
ver
250
0,32
0,52
0,81
1,3
2,1
3,2
5,2
– 0
0
0
0
0
0
0
±0
,65
±1,0
5±1
,6±2
,6+
0,71
+0,
32+
0,52
+0,
81+
1,3
up
to
315
–0,3
2–0
,52
–0,8
1–1
,3–2
,1–3
,2–5
,2+
0,19
0 0
0 0
ove
r31
50,
360,
570,
891,
42,
33,
65,
7–
0 0
0 0
0 0
0±0
,7±1
,15
±1,8
±2,8
5+
0,78
+0,
36+
0,57
+0,
89+
1,4
up
to
400
–0,3
6–0
,57
–0,8
9–1
,4–2
,3–3
,6–5
,7+
0,21
0 0
0 0
ove
r40
00,
40,
630,
971,
552,
54
6,3
– 0
0 0
0 0
0 0
±0,7
75±1
,25
±2±3
,15
+0,
86+
0,4
+0,
63+
0,97
+1,
55u
p t
o50
0–0
,4–0
,63
–0,9
7–1
,55
–2,5
–4–6
,3+
0,23
0 0
0 0
1) N
ot
con
tain
ed in
ISO
286
–2
T.059
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Tables / tolerances /standards
SI units system
1. Basic units of the SI system
Quantity Name Symbol
Length meter mMass kilogram kgTime second sElectric current ampere AThermodynamictemperature kelvin KLuminous intensity candela cdAmount of substance mole molPlane angle radian radSolid angle steradian sr
2. Derived SI units
Quantity Name Symbol Defining equation
Frequency hertz Hz 1 Hz = 1 s–1 = 1/sForce newton N 1 N = 1 kg · m/s2
Pressure and mechanical stress pascal Pa 1 Pa = 1 N/m2
Work (energy, heat) joule J 1 J = 1 N · m = 1 W · s
Power, energy flow, heat flow watt W 1 W = 1 N · m/s = J/sElectrical charge, quantity of electricity coulomb C 1 C = 1 A · sElectrical potential,potential, difference voltage volt V 1 V = 1 W/AElectric capacitance farad F 1 F = 1 A · s/V
Impedance ohm Ω 1 Ω = 1 V/AElectrical conductivity siemens S 1 S = 1 Ω–1 = 1/Ω = 1 A/VMagnetic flux weber Wb 1 WB = 1 V · sMagnetic flux density tesla T 1 T = 1 Wb/m2
Inductance henry H 1 H = 1 Wb/A = 1 V · s/ALuminous flux lumen lm 1 lm = 1 cd · srIllumination lux lx 1 lx = 1 lm/m2
Conversion tables
Conversion table for units of force Conversion table for units of mechanical stress
SI is the modern system of units for measurement, accepted andused world wide. It is used in all areas of international standardsand is commonly referred to as the metric system. SI is used in allareas of science, technology and trade and is applied in the sameway world wide.
SI is built of: Base unitsSupplementary unitsAdditional unitsPrefixes
The figures given in the conversion tables are roundedup to 3 or 4 digits.
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1 milligram1 ppm (part per million) per 0,001 g/kgis 1 part out of 1 million parts kilogram (10–3)
2700 litres1 ppb (part per billion) 1 microgramis 1 part out of 1 billion parts per 0,000 001 g/kg
Example: (b = billion, US English for milliard) kilogram (10–6)one lump 2,7 million litresof sugar 1 ppt (part per trillion) 1 nanogramdissolved in: is 1 part out of 1 trillion parts per 0,000 000 001 g/kg
(t = trillion, US English for billion) kilogram (10–9)2,7 billion litres
1 ppq (part per quadrillion) 1 picogramis 1 part out of 1 quadrillion parts per 0,000 000 000 001 g/kg(q = quadrillion, US English for billiard) kilogram (10–12)
2,7 trillion litres
Tables / tolerances /standards
Conversion tables
Conversion table for units of work, energy and heat
Value Previous unit Symbol New unit Symbol Defining equationLength Ångström Å meter m 1 Å = 10–10 mPressure mm mercury mm Hg pascal Pa 1 mm Hg = 133,3 PaEnergy Erg erg joule J 1 erg = 10–7 JPower horsepower PS watt W 1 PS = 735,5 WDynamic viscosity Poise P pascal · second Pa · s 1P = 0,1 Pa · sKinematic viscosity Stokes St cm2/s 1 St = 1 cm2/sImpact value kpm/cm2 J/cm2 1 kpm/cm2 = 9,087 J/cm2
Heat capacity kcal/°C J/K 1 kcal/°C = 4,187 · 103 J/KHeat conductivity kcal/m.h °C W/K · m 1 kcal/m · h · °C = 1,163 W/K · mSpecific heat kcal/kg °C J/kg · K 1 kcal/kg · °C = 4,187 · 103 J/kg · KMagnetic field strength Oersted Oe ampere / meter A/m 1 Oe = 79,6 A/mMagnetic flux density Gauss G Tesla T 1 G = 10–4 TMagnetic flux Maxwell M Weber Wb 1 M = 10–8 WbLuminous intensity internat. candle IK candela cd 1 lK = 1,019 cdLuminance Stilb sb cd/m2 1 sb = 104 cd/m2
Absorbed dose Rem rem J/kg 1 rem = 0,01 J/kgIon dose Röntgen R C/kg 1 R = 2,58 · 10–4 C/kg
Conversions of part volumes
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Tables / tolerances /standardsConversion tables
metric – USAUSA – metric
metric – USA1 millimeter (mm) 0,039337 inches (in.)1 centimeter (cm) 0,39370 inches (in.)1 meter (m) 39,3700 inches (in.)1 meter (m) 3,2808 feet (ft.)1 meter (m) 1,0936 yards (yd.)1 kilometer (km) 0,62137 miles (m.)
Measures of lengthUSA – metric1 inch 25,400 mm1 inch 2,540 cm1 foot 304,800 mm1 foot 30,480 cm1 foot 0,3048 m1 yard 91,4400 cm1 yard 0,9144 m1 mile 1609,35 m1 mile 1,609 km
The figures in brackets represent hardness values beyond the definedscope of the standardised hardness test but which are frequently used asappoximate values in practice. Furthermore the Brinell hardness values in brackets are only valid if the test was carried out with a hard metal ball.
1) Calculated with: HB = 0,95 · HV
The comparison table below is valid only for carbon steels, lowalloy steels and cast steels in the hot formed and heat treatedcondition.
For high alloyed and / or cold headed steels [4.8. 5.8] (6.8. A1 toA4) there are considerable differences to be expected.
The Vickers testing method is applicable over a wide hardness range. The referee method per ISO 898/1 is the Vickers method.The Rockwell C method is suitable for hardened steels, Rockwell A for sintered steel and Rockwell B for soft steels, copper alloys,etc. The Brinell hardness method extends over a wide hardness range too.
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Tables / tolerances /standardsDesignations of different national
This catalogue is protected by the laws of intellectual propertyand competiton. All rights are reserved, including reproduction,translation and recording and processing in electronic datasystems.
Copyright 2001 by Bossard AG Schrauben, CH-6305 Zug