What is honing? · 2020-03-09 · machining, which is about 1/20th of that of general grinding wheels. 2. General grinding is line contact processing. Honing is surface contact processing.

What is honing? Honing processing is a polishing process mainly combining rotational motion and reciprocating motion on the cylindrical inner peripheral surface. Characteristic

1.Processing distortion is small at about 30 to 100m of low speed machining, which is about 1/20th of that of general grinding wheels. 2. General grinding is line contact processing. Honing is surface contact processing.

3. It acts as a  lubrication as a sliding surface and an oil reservoir of a 

rotating part.

Trend of honing processing！

In  recent  years,  it  has  been  mainly  used  in  combination  with 

superabrasive  grains  (diamond  · CBN),  and  it  is  showing  great 

effect in automobile industry etc.

Photo

Engine block production line

Benefit of honing processing!

Cycle reduction is possible.      Example: Improvement of occupancy rate through production 

automation and cycle shortening.

Improve circularity.    Example: Engine cylinder intersection, within a few microns.

The  surface  roughness  is  stabilized.    Example:  Mainstream  processing  method  for 

automobile engine production.

Cost  reduction.        Example: Great  combination  cost  reduction  effect with  superabrasive 

grains (diamond · CBN).

1.6.1 Outline of Honing

(1) Honing basics

Honing is a technique in which a grinding stone is

pressed against a work surface while rotating and

reciprocating motion is applied to a grinding stone held

by a fixture and a workpiece and a grinding stone are

kept in a constant surface contact state while pouring a

large amount of working liquid, Shape, and surface

roughness of the workpiece. The honing has the largest

inner surface of the cylinder but also to the outer

surface and the flat surface.

Figure 16.01 shows the simplest method of internal

honing work. In other words, the cylindrical degree of

the hole is improved in the reciprocating direction from

the motion state of the grindstone, and the roundness is

improved in the rotating direction.

In Fig. 16.01, the axial distance, that is, the honing

stroke S, at which the whetstone moves on the work

surface is S = L + 2t - р.

Where L is the work piece length, t is the over travel,

and ℓ is the grindstone length. Also, on the honing

surface, a reciprocating motion is given to the

grindstone in the same way as the rotation, and a

specific intersecting meshed finished surface can be

obtained. (Figure 16.02). This mesh-like intersecting

angle is called (cross hatch angle).

Cross angle 2α = 2 tan - ¹ Vs / Vr・・・・・(2)

The synthesized speed of the circumferential speed V 1

and the reciprocating speed Vs is referred to as a

honing speed V.

VටV²r＋V²s・・・・・・・・・・・・・・・(3)

Wheel expansion allows pressing between the grinding

wheel and the workpiece by pushing the expansion rod

inside the honing tool and extruding a conical cone

which is in contact with the wheel head and serves to

press the grindstone against the workpiece. (Fig. 16.01).

(2) Honing machine

The honing machine has a vertical shape in which the

processing hole is made vertical, and a horizontal shape

in which it is processed horizontally. For inner honing,

normal standing is used.

Many of the recent honing machines are fully

automated honing machines equipped with multiple

1.6 Honing

axes for high efficiency, automatic sizing devices,

automatic supply devices for workpieces, etc., as well

as high speed conveying devices and the like.

Recently, new control technologies such as automatic

corrections necessary for processing the optimum

hole shape in the honing process have been

developed, to ensure the elimination of defective

products and the stabilization of product precision.

In the automatic honing machine, as a basic method

(Fig. 16.03) for expanding the whetstone, the

grindstone is expanded with a constant pressure

against the workpiece by hydraulic pressure (1)

constant pressure expansion method (constant

pressure cut) and the expansion (2) machine

expansion method (constant speed cut) is carried out

while regulating speed by sending. In the machine

expansion method, since the control of the grindstone

expansion amount is simple, it is easy to digitize and

NC. Furthermore, cubic boron nitride (CBN) or

synthetic diamond 1 (SD), which is difficult to abrade

or wear away from abrasive grinding edge, which is

easy to maintain minute amount honing due to fine

incisions due to hard and tough properties Honing

machines of the machine expansion method using

super abrasive grinding wheels tend to increase.

In honing processing, it is basically important

that the grindstone follows the central axis of the

machined hole. From this it is clear that the

fixture always has the center of the grinding

stone at the center of the machining hole during

machining, the honing head and the machining

hole are self-aligned and the honing pressure

equals the whole machining hole by free cutting

Equipment is necessary.

Therefore, considering the weight and shape of 

the workpiece, it is necessary to decide whether 

to fix the fixture (rigid type) or swing type (float 

type).  In  general,  when  the  workpiece  is 

lightweight  and  compact,  let  it  float.  If  the 

workpiece  is heavy  in weight,  float  the honing 

tool and fix the fixture. (Fig. 16.04).

In addition, when actually operating  the honing 

machine,  the  conditions  to be provided by  the 

honing machine are  satisfied, and  the  thermal 

displacement amount and the work accuracy of 

each  part  of  the  machine,  the  change  of  the 

cutting speed due  to  the  temperature  rise, etc. 

are necessary.

1.6.2 Honing mechanism

(3) Honing stones

The indication of the honing grindstone is displayed according to JIS R 6210 (vitrified grinding wheel) when conventional alumina material and silicon carbide abrasive grains are used. Superabrasive grains such as diamond and cubic boron nitride (CBN) abrasive grains are displayed according to JIS B 413 (diamond and cubic boron nitride wheel).

Fig.16.0    shows  a  display  example  of  a  honing 

grindstone. FIG. 1 shows various shapes of a honing 

grindstone. The mold type grinding stone prevents damage such as grinding wheel chipping, improving the grinding wheel life, and improving the effect of grinding wheel management greatly. Also, the abrasive grain reamer with superabrasive grains attached by electrodeposition method achieves high efficiency honing by passing the inner surface of the hole one or two times at low stroke speed, and high precision can be achieved even with drilled holes with notches It is easily possible.

Honing is as slow as 1 / 50th of the grinding process. Further, the workpiece and the grinding stone are processing methods for efficiently finishing

the surface of the workpiece in surface contact with the line contact of the grinding process. Such a cutting mechanism having such characteristics is fundamentally important for honing.

In  honing,  cutting  is  performed  with  the 

grindstone and the workpiece  in surface contact. 

For  this  reason,  except  for  green  in  the  cutting 

direction  of  the  grinding wheel,  since  chips  are 

required to escape from the grindstone surface, it 

is  not  easy  to  generate  continuous  chips, 

resulting in massive chips. Of course, in this case 

the discharge of the chips becomes a problem.

(1) Chip generation

  Fig.16.06 and Fig. 16.07 show  the case where 

bearing steel is internally ground and honed with 

CBN grindstone respectively. In internal grinding it 

is  a  continuous  chips  of  flow  type,  whereas  in 

honing bulky discontinuous type chips are mainly 

used. Fig. 16.08 and Fig. 16.09 are honed cast 

irons, both of which are granular sandy chips.

    Fig. 16.10 and Fig. 16.11 are the observation of 

the work  surface  of  the  grindstone  at  this  time. 

(2) Cutting mechanism of honing

In the vitrified honing grinding stone using conventional alumina and silicon carbide abrasive grains, (1) falling cutting (dressing period), (2) steady crushing cutting (steady cutting period), (3) eye It is known to take three forms of clogging (loading cutting). For example, in a honing grindstone that fills the pores of a vitrified grinding stone, the purpose of the loading cutting is to continue the cutting force while maintaining a constant value at all times because the loading depth from the grindstone surface is small. Figure 16.12 shows the four wear forms of the honing grindstone.

(3) Action of Metal Bond Wheel

which  are  harder  and  more  tough  than 

conventional  abrasive  grains  are  actively 

adopted. The bonding agent (bond) applied to this 

is mostly metal bonds  that have better abrasion 

resistance than other bond types.

Figure 16.13 shows a cutting model diagram of a metal bonded grinding stone, and the generated chip abrades the front metal bond layer of the abrasive grain to make a crater. On the other hand, each abrasive grain is responsible for honing in two directions, so the

In  recent  honing  processing,  super  abrasive 

grains such as diamond and CBN abrasive grains

1.6.3   Honing condition and finishing performance

  chips flow around the side of the abrasive grain and make a V-shaped groove as shown in Figure 16.14. This groove serves as a flow path, and  the chips are conveyed behind  the abrasive 

grain  and  discharged. Therefore,  if  the  grinding 

stone width is wide, the chips which lose escape 

place are interposed between the grindstone and 

the  workpiece,  causing  scratches  on  the 

processed surface.

For this reason, in superabrasive metal bond whetstones, the width of the conventional alumina grindstone is 10 to 12 mm, whereas it is narrowed to 3 to 4 mm so that chips are easily discharged.

  In order to raise the machining efficiency by honing work and to satisfy the accuracy of the target, it is necessary to select the correct grinding stone together with an appropriate honing condition. Figure 16.15 shows basic conditions that affect honing performance, and Table 16.02 shows honing characteristic values corresponding to four elements for processing purposes.

  Figure 16.16 shows the results of internal diameter honing of mild steel as a hydraulic cylinder - part by constant pressure cutting method. The specification of WA grinding wheel is  currently  widely  used  in  this  part  processing 

and we  are  testing CBN  and SD whetstone  for 

comparison.  The  crossing  angle  is  changed  by 

changing  the grinding wheel  rotation speed with 

the reciprocating speed constant and accordingly, 

with  a  constant  machining  time,  the  traveling 

distance  increases  as  the  crossing  angle 

decreases.

(2)Cross angle and finish performance

(3) Wheel pressure and finishing performance

 When both the thrust and the circumferential force are 

organized and compared by  the expanding force of the 

whetstone  in  both  the  constant  pressure  cut  and  the 

constant speed cut and the expansion force is the same 

as  the constant pressure cut  in constant speed cutting, 

The  machining  efficiency  shows  the  same  value  and 

increases in proportion to the expansion force.

(4) Honing speed and finishing performance

  The  reciprocating  speed  of  the  grinding  wheel  is 

limited from the machine and is currently in the range 

of 5 to 25 m / min. Therefore, the grindstone rotation 

speed is usually 15 to 40 m / min for a conventional 

grinding  wheel  and  35  to  80  m  /  min  for  a  super 

abrasive grindstone Speed honing is preferable.

Figure 16.18 shows the specific material removal rate (㎤ / min / ㎠) as the chip removal efficiency per unit time per 1 ㎠ surface area. In the WA grinding wheel, there is a tendency that the efficiency tends to be the maximum in the vicinity of V = 60 m / min (2.alpha. = 30 degrees), but in superabrasive whetstones the specific material removal rate also increases as V increases. This  is 

proportional  to  an  increase  in  the  travel  distance  L 

shown in the figure. On the other hand, the amount of 

honing  (㎤  / m  / ㎠)  at  unit  travel  distance  per  1 ㎠ 

surface  area  of  the  grinding  wheel  is  higher  for  the 

super  abrasive  grinding wheels  as  the  2  α  becomes 

larger.  Therefore,  in  order  to  perform  high  efficiency 

honing with honing operation with constant processing 

time  by  super  abrasive  grinding  wheels,  the  honing 

speed must be  increased and the number of abrasive 

grain working cutting edges must be increased in order 

to increase the running distance.

  As compared with superabrasive grains, abrasive 

grains are easy  to break, and  in  the WA grinding 

wheel with a large amount of wear abrasion, there 

is  a  maximum  value  of  honing  amount  in  the 

vicinity of an  intersection angle of 30 degrees. On

the other hand, with superabrasive grinding

wheels, the honing amount tends to increase as

the crossing angle decreases, that is, as the

running distance increases

Figure  16.17  shows  the  finishing  performance 

against grindstone surface pressure, both grinding 

wheel abrasion and honing value  increases as  the 

wheel  surface  pressure  increases. With  the  same 

grinding wheel surface pressure, the honing amount 

of the SD grinding wheel is smaller than that of the 

CBN grindstone.

Figures 16.22  to 16.24 show  the  results of  inner 

diameter honing of gears by metal bonded CBN 

whetstone in the case where the taking amount is 

constant at 0.02 to 0.04 mm in diameter.

  As shown in Figure 16.22, the processing time T 

becomes  shorter  due  to  the  increase  of  the 

grindstone pressure Pn, but  the grindstone wear 

amount S also increases sharply  in proportion to 

Pn, so  it  is not preferable  to simply set  the high 

pressure condition. Also  in Fig. 16.23, when  the 

low pressure is 30 kgf / ㎠, T is greatly shortened 

by  increasing  the  grindstone  rotation  speed Ｖ, 

which  is  efficient.  Therefore,  as  a  honing 

condition,  the grinding wheel surface pressure  is 

a lower pressure, and Ｔ  is greatly shortened by 

increasing the grindstone rotation speed, which is 

efficient.

The  smaller  the  crossing angle 2α,  the  shorter 

the T is, the higher the efficiency is. This is due to 

the  influence of the grindstone rotation speed. In 

Figure 16.24, as the grinding wheel reciprocating 

speed  V  increases,  T  is  shortened  and  high 

efficiency  is obtained, but S  is  increased on  the 

contrary. The  lowering of  the grinding wheel  life 

becomes conspicuous as the pressure increases.

(5) Constant speed cutting and finishing performance

  It  is  the  most  ideal  if  a  fixed  speed  cutting 

method  in which  the  grinding  stone  expands  in 

the radial direction at a constant speed, and if the 

setting amount equal to the extension amount of 

the setting can be obtained.

  Figure  16.20  compares  the  honing  amount W 

with the set cutting depth ｄ  for the conventional 

WA  grinding wheel  and  the CBN  grindstone.  In 

the  CBN  grindstone,  the  cutting  amount  of  the 

setting is almost satisfied, and in the WA grinding 

stone,  the cutting allowance  is about 30  to 40%. 

In addition, Figure 16.21  shows  the  relationship 

between Ｗ  and  dressing wear Ｓ with  respect 

to ｄ,  indicating  that  the  sum  of Ｗ  and Ｓ  is 

approximately  equal  to  ｄ .  That  is,  in  the 

constant  velocity  incision,  if  the  stiffness  of  the 

grinding wheel  incision  system  is  sufficient,  the 

sum of Ｗ  and Ｓ  substantially matches ｄ.

Therefore,  super  abrasive  grains  which  are 

superior  in  cutting  ability  compared  to 

conventional  abrasive  grains  easily  without 

crushing  or  blurring,  are  very  convenient  for 

constant speed cutting which forcibly removes the 

margin by cutting amount .

1.6.4   Honing surface

(2)It is obtained from a unique mesh (cross hatch)

finished  surface  depending  on  the  grindstone 

rotation speed and the reciprocating speed and 

plays a role of oil holding at the sliding surface 

and  rotating  contact  portion,  giving  a  good 

result of lubrication action.

(3) In addition to the usual honing finish surface, 

a  plateau  surface  finish  that  combines  the 

advantages of groove depth with coarse honing 

and the smooth surface finish is possible.

  (4)  The  processing  strain  of  the  honed  surface 

layer  is small and excellent surface quality  is 

obtained.

(1) Characteristics of honing surface

  The characteristics of the honed finished surface 

are as follows.

(1) Surface finish of about 0.3 S or more can be 

freely  selected  by  appropriately  combining 

the  grinding  stone  ·  honing  speed  ·  cutting 

speed · honing oil agent etc.

(2) Display of finished surface roughness

 On  the  honed  surface,  it  is  expected  that  the 

surface  shape  and  roughness  value  will  differ 

depending on  the direction  to be measured, since 

there are peculiar  intersecting marks of  the marks 

traveled by  the abrasive grains. The grindstone  is 

actually  measured  in  the  case  of  the  constant 

pressure outer circumference honing, and it is said 

that  it  may  be  measured  from  either  the 

circumferential  direction  or  the  axial  direction, 

except when it is peculiar that the intersection angle 

2α is around 0 ° or 180 °.

(3) Surface roughness and grindstone selection

Figures 16.25 and 16.26 show  the  relationship 

between  grindstone  grain  size  and  finished 

surface  roughness  for  various  work  materials. That  is,  as  the  grain  size  of  the  normal  honing 

grindstone  becomes  finer,  the  finished  surface 

also becomes  finer. However, when  the amount 

to  be  removed  is  relatively  large  and  a  good 

finished  surface  is  required,  it  is  necessary  to 

efficiently  remove  the  required  margin  with 

coarse  grain  size  by  two-step  machining  and 

finish  the  finish  with  finer  grain  size,  so  that 

economical  honing  Processing  is  possible.  In 

Figure  16.27,  it  is  more  efficient  to  perform 

general  abrasive  grinding  than  super  abrasive 

grinding  to  perform  a  fine  surface  finish  of  less 

than 3 μm R (3 μRmax) or less.

Normally,  the  roughness of  the honing surface  is 

measured in the axial direction, and Rmax and Rz 

are  used  in  Japan.  In  addition,  the  surface 

roughness  standards  of  each  country  are 

exemplified as shown in Table 16.03.

Therefore, in case of needing a surface finish of 3 μm

Rt (corresponding to 3 μm Rmax) or less by honing

process of cast iron with large amount of taking-out

etc. in mass production etc., it is possible to perform a

high honing by coarse honing with super abrasive

grains and then finish honing with general abrasive

grains Efficiency, economical and stable quality parts

are guaranteed.

Table 16.04 shows how to select abrasive grain type 

and grain size with respect to the desired surface 

roughness for various work materials to be honed.

(4) Plateau Honing

The  inner surface of  the engine cylinder  is honed at 

the  final  stage.  In  this  case,  familiar  operation  is 

substantially  reduced  by  creating  a  surface  finish 

structure  called  plateau  honing. The  valley  of  the 

honing  surface with an appropriate  interval provides 

an ideal oil pocket, and as a result it has an effect on 

consumption  and  life  of  engine  oil.  Figure  16.28 

shows the plateau honing state of the inner surface of 

the cylinder, the cross sectional profile of the finished 

surface giving rise to the Abbott Contact Curve.

Abbott  contact  curves  show  the  percentage  of  the 

cumulative  contact  area  with  respect  to  the  valley 

depth of  the cross-sectional curve of different cutting 

finished  surfaces  and  are  controlled  so  that  the 

pattern of the curve falls within a certain intersection.

Figure 16.29 shows the plateau honing process.

  In actual production,  for example, coarse honing  is 

due to mechanical expansion and plateau honing is by 

hydraulic expansion.  In addition,  it has  two stages of 

expansion mechanism with  one  axis,  the  set  of  two 

different kinds of different honing stone are alternately 

expanded.

When high speed honing is carried out by using super 

abrasive grains, 

the cutting  temperature becomes high as a matter of 

course, the influence of temperature and surface flow 

on the depth and residual stress of the work-affected 

layer is concerned. Figure 16.30 shows the results of 

examining  these. Depth  0  represents  the machined 

surface by honing, and the honing margin is about 30 

μm. From  this  figure,  tensile stress disappears when 

honing, and residual compressive stress occurs.

(5) Residual stress on honed surface

Table 16.05 compares the finishing performance 

when using GC  (SC) wheels and diamond  (D) 

wheels,  respectively,  with  plateau  honing  by 

finishing honing after coarse honing.

1.6.5 Take off honing

(1) Guidelines for removal

  In the honing process, it is scraped off from the first 

high portion, and  the  final size  is obtained  in a state 

where  the  whole  is  honed.  Therefore,  the  honing 

margin  is  usually  determined  by  the  pre-processing 

precision.

In general, the minimum mating honing magazine is 

theoretically  given  as  the  sum  of  the  prefabricated 

surface  roughness  twice  amount  and  the 

pre-processing dimensional error such as roundness, 

cylinder degree, straightness and the like.

    Although  it  is most  economical  to  set  the  honing 

margin as minimum as possible,  for  large holes with 

large  waviness  of  pre-machining  or  tape,  twice  the 

sum  of  pre-machined  surface  roughness  and 

pre-machining  dimensional  error  We  need  honing 

margin of quantity.

(2) Take off ~ practical example of processing time

 Normally, honing time for small parts is small, but it is 

a  problem  in  case  of  large  parts.  Table  16.07  is  a 

guideline  for  the  time  required  to  eliminate  the 

required margin

  Table  16.08  and  Table  16.09  show  the  removal 

amount  and  processing  time  in  various  honing 

operation examples using super abrasive grains.

  In  general,  the  cutting  action  and  thermal  stress 

cause  tensile  residual stress, and  the basini effect 

produces compressive stress. Therefore,  it can be 

said  that  the  influence of  the basini effect  is  larger 

than  that  of  the  cutting  heat  even  in  high  speed 

honing.  In  this  figure,  the depth of  the  influence of 

the honing process is about 50 μm, and the depth of 

the  altered  layer  as  a whole  is  dominated  by  the 

machining as the pre-processing.

1.6.6 Processing precision

(1) Modification of cylindrical shape and circularity Generally, in honing processing, by floating either the tool or the workpiece, the honing

head and the processing hole are automatically aligned so that automatic cutting can be

continued. That is, by uniformly expanding the grinding stone to the inner surface of the hole,

the tool is further subjected to the reciprocating motion of the grinding stone having an

appropriate length and rigidity at the same time, The shape error occurring in the

pre-processing is corrected with the minimum allowance amount, and improvement in

geometrical shape accuracy such as cylinder degree, roundness, surface roughness and

the like is obtained.

In order to obtain accurate cylindricity by honing processing, it is necessary to accurately

adjust the stroke length and the stroke position. That is, the cylinder degree is closely

related to the number of abrasive particles passing through an arbitrary point on the

processed surface of the workpiece, that is, the honing amount. Before and after the

moment when the grindstone overruns at the end of the workpiece, the cutting amount

increases as the wheel surface pressure increases.

Also, it is known that the roundness is closely related to the surface roughness, and by

cutting the grinding stone and applying run-out or multistage honing equivalent to spark-out

of the grinding process, the finish surface roughness Roundness is also improved with

improvement.

(2) Automatic sizing device One of the reasons why honing has become widely used is that it is a processing method

that facilitates automatic sizing by in-process.

The automatic sizing in honing work is shown in Table 16.10.

However, the current automatic sizing is about the control of the machining allowance in the

strict sense, and it does not automatically control finish surface roughness, roundness,

cylinder degree, and the like.

(3) Multistage honing and high efficiency and high precision machining Injection pump parts (Fig.16.32) heat treatment after deep hole drilling and immediately

honing. The removal allowance is in the range of 0.1 to 0.215 mm depending on the hole

diameter.

By using this as a honing process divided into three or four stages, high precision can be

easily obtained. In this multistage honing, in the first step, the rate of removal is increased,

and in the subsequent step, a small amount of removal that emphasizes surface finish is

allocated.

Also, a CBN metal bond grinding stone having excellent cutting performance is used for the

work hard material.

As shown in Figure 16.33, surface roughness and geometric accuracy are improved in

stages by using fine grinding wheels. For example, the shape accuracy decreases to 1/2 for

each step, and the accuracy is improved.

In this processing, good results can be obtained from the viewpoint of improvement of

machinability and accuracy as compared with continuing pressurization by hydraulic

expansion by extending the honing tool slightly by machine expansion.

Furthermore, in this machining, the diameter measurement and the stroke position are

converted by the sizing station having the automatic feedback, and the cylindrical shape is

automatically corrected.

Practical application of adaptive control honing is desired because it mass-produces stable

parts with excellent uniformity and does not produce defective products. However, as a

practical matter, the reason why quality control is difficult during the honing process is

honing result cannot be reproduced. The reasons are listed below.

1) Friction force in cutting system

2) Rigidity problem in tools and workpiece systems

3) Changes in grinding performance during honing

4) The state of the sharp edge of diamond or CBN honing tool is unclear.

5) Changes in honing processing affected by the state of the grindstone working surface

caused by various wear forms

6) Variation of pre-processing dimension of workpiece

Here, regardless of the surface condition and honing condition of the honing grindstone, it

was produced by honing based on the linear correlation (Fig. 16.34) between the measured

values of the tangential force ratio μt and the surface roughness Rz It is intended to manage

the surface roughness by measuring the tangential component force Ft in the rotational

direction and the torque. (Figure 16.35)

In this case, however, the types of the grindstone, workpiece material and coolant are

limited.

In other words, if the surface roughness is finer or rougher than the required value, the

vertical component force (grinding wheel pressing force) Fn is corrected by increasing or

decreasing the hydraulic pressure.

However, since the machine cannot calculate Fn in the extended form, in this case, it is

nothing other than directly managing the surface roughness during machining.

Figure 16.37 shows a calibration chart when using the roughness sensor (Fig. 16.36)

attached to the groove of the honing head and an example of measuring the surface

roughness during honing.

1.6.7 Selection of honing stone

(1) Grindstone selection criteria In the honing grindstone, the selection of the correct honing grindstone becomes important

from the viewpoint of accuracy, efficiency and economy. Compared with conventional

abrasive grains, hard and tough superabrasive grains are excellent in abrasion resistance,

and the cutting edge of the abrasive grains is firm.

Particularly, it is easy to control the expansion amount of the grindstone even for minute

cuttings such as machine expansion method, so the practical application of superabrasive

grinding wheels such as diamond and CBN is rapidly expanding.

On the other hand, since honing has low speed and little heat generation due to processing,

active selection of diamond abrasive grains and the like is being put to practical use.

(a) Grindstone selection for work material

Table 16.11 shows the selection of general abrasive grinding wheels. In the case where

the work material is steel, alumina (Wa, A) abrasive grains are usually used, and in the

case of cast iron, silicon carbide (CG, C) abrasive grains It is selected as standard.

And, for the purpose of economical grindstone performance with less grinding wear

abrasion and excellent machinability, a processing grinding stone is used which softens the

degree of bonding of the grinding stone base body and fills the grinding stone pores with

sulfur (S). Table 16.12 shows selection of super abrasive wheels. CBN abrasive grains are

typically chosen for honing of heat treated hard steel whereas diamond (SD) abrasive

grains are selected for hard brittle materials, cast iron, mild steel and the like.

In order to facilitate the discharge of chips using a metal bond grinding stone or to promote

the cutting action of abrasive grains during constant pressure cutting by enlarging the

interval between abrasive grains, the concentration is preferably lower.

(b) Particle size selection for finished surface roughness

Table 16.13 and Table 16.14 show the particle size selection for finish surface roughness

for general abrasive grains and super abrasive grains.

In superabrasive grains, it is necessary to select a mesh number that is 1.5 to 2 times as

large as that of general abrasive grains on average.

(c) Example of selecting a honing stone

Table 16.5 shows selection examples of conventional grinding wheels and superabrasive

grinding wheels in honing of automobile parts. Whereas conventional whetstones handle

sulfur with vitrified bonds, metal bonds with the highest wear resistance among various

bond systems are standardized for superabrasive grains.

Particularly recently, bronze-based crushable metal bonds which promote the blade

function and emphasize machinability are frequently used.

(2) Performance evaluation of honing stone In honing processing, there is a honing ratio (cutting removal volume / grinding wheel

abrasion volume) corresponding to the grinding ratio in the case of grinding as a method for

evaluating the performance of the honing grindstone. That is, when a super abrasive

grinding wheel which is expensive compared with the conventional general grindstone is

used, a high honing ratio is desired.

However, pursuing only this makes it difficult to maintain favorable machinability.

Therefore, it is necessary to evaluate the total cost, such as shortening of processing time

besides grinding wheel cost, greatly decreasing the frequency of grindstone replacement

by improving the grinding wheel life, not only improving productivity but also saving labor

cost and overhead cost is there. Table 16.16 shows data on the honing ratio and the cutting

removal volume per unit time at that time, that is, the honing efficiency, for the example of

workpiece per set of grinding wheels with respect to grinding wheel life. Table 16.17 shows

this comparison in comparison between conventional grinding wheels and superabrasive

grinding wheels. At the same time, the average grinding wheel wear amount per workpiece

is also shown.

(3) Shape accuracy of super abrasive grinding wheel

With ordinary grinding wheels, the grindstone wears as the honing process progresses and

adapts to the machined surface, so that the precision of the imaginary cylinder formed by

the grindstone surface, that is, the cylindricalness of the honing head improves in a state

where the grindstone is attached to the honing head.

However, with super abrasive grinding wheels, wear is very low, so we can hardly expect

this cylindrical degree correction function. Therefore, for super abrasive grinding wheels

such as CBN, diamonds need to be delivered with accuracy of 0.010 mm or less in

cylindrical shape of honing head before use by truing. In general, a honing head is used as a

truing jig, a grinding stone is attached to the honing head, and the workpiece finished or a jig

having the same hole diameter as that of the workpiece is used to expand the honing head

so as to closely contact the grindstone Fix and sharpen the cylinder to a predetermined size

with reference to the center.

In order to ensure a better cutting action, it is possible to dress with a GC grinding wheel

with fine grain than the grain size used for the honing grindstone, soft wet GH hardness

without losing shape accuracy of the honing grindstone obtained by truing it is important to

remove metal bonds between abrasive grains to create small chip pockets. Besides this, as

a dressing method of a metal bond grindstone, there is a mist electric discharge machining

and the like.

1.6.8 Selection of the honing oil

(1) Procedure for selecting oils Generally, as a honing oil agent, a water-insoluble oil blended with a low viscosity mineral

oil as a base oil, various oiliness agents and extreme pressure additives is used. Basically,

the following three actions are required.

1) Lubrication at abrasive grain cutting edge application point

2) Cleaning action to carry out cutting and grinding wheel abrasion

3) Cooling action to reduce heat generation

Honing oil is included in the classification of JIS/ K2241 cutting oil.

In choosing the actual horn oil, it is selected in consideration of the viscosity, the type and

amount of additives, as well as the flash point, safety and hygiene, etc., based on the

working materials and horn conditions.

Viscosity affects processing efficiency and finished surface roughness.

Normally, when the viscosity is high, the finished surface roughness is improved, but the

working efficiency is lowered.

Addition of additives such as oiliness agents and extreme pressure agents gives good

results to the finished surface roughness and honing ratio, and in some cases troubles such

as scratches caused by the grindstone, chatter marks, grinding wheel defects and the like

can be prevented.

In addition, management of oil agent in honing processing is very important in minimizing

fluctuation in grindstone performance so that mass production can be performed stably with

high precision processed products without issuing defective products. The important

management items are as follows.

1) Filtration management of oil agent

Mixing abrasion powder and chips of the grindstone in the oil agent causes deterioration of

the finished surface or scratches. Also, these mixtures may adversely affect grinding wheel

life. Therefore, it is necessary to select an appropriate filtration device according to the

purpose of processing and always use the oil agent in a clean state.

2) Temperature control of oils

In order to reduce dimensional variations of workpieces and to maintain stable processing

performance, the viscosity of the lubricant must be constant. For this purpose, it is

necessary to control the temperature of the oil agent. For example, with a cooling device or

a humidifier, the oil agent is sent to the honing zone at a constant temperature of 20

degrees.

3) Property management of oil agent

The occurrence of various troubles can be prevented by periodically performing the property

management of the appearance, viscosity, additive concentration, sucking tail, inclusion and

the like of the honing oil agent beforehand to prevent deterioration of the oil agent.

(2) Practical use of water-soluble oil Along with the automation and labor saving of production lines, the need to convert from

water insoluble oil to water-soluble oil is persistent from fire prevention, environmental

hygiene, centralized refueling and the like in factories.

However, water solubilization by honing has various problems due to changes in oils,

machinery and grindstone performance, and it is currently difficult to put it into practical use.

Normally, when a water-soluble oil is used, a paste-like sticky substance adheres to the

surface of the whetstone, resulting in a severe clogging state, making normal honing difficult.

This is said to be due to a part of the surfactant contained in the water-soluble oil becoming

a water-insoluble sticky substance and adhering to the surface of the whetstone. The test oil

in Table 16.18 was used for the honing of the sintered alloy shown in Figure 16.39 for the

purpose of commercializing water-soluble oil. Experiments were conducted with varying

dilution concentrations for standard water insoluble oils as honing oil using an emulsion type

and a soluble type, which are superior to lubricity as compared with solution type.

Fig. 16.40, Fig. 16.41 and Fig. 16.42 show honing performance by diamond (SD), CBN

whetstone and conventional GC whetstone. Both of the grinding wheels are of high

emulsion type and good results are obtained especially for SD grinding wheels.

Both of the grinding wheels are of high emulsion type and good results are obtained

especially for SD grinding wheels. In addition, the finished surface roughness was the SD

and CBN grindstone for the GC grindstone of 0.8 to 1.5μmRz.

1.6.9 Single pass honing

As a recent honing technique, there is single pass honing (single pass honing or single

stroke honing). Unlike ordinary honing which repeatedly makes a stroke with a rotating

honing tool, it intends to remove all the removal allowance intensively with one stroke.

Figure 16.43 illustrates the single pass honing technique.

As a tool, an electrodeposition grinding stone of super-abrasive grains of a long life such as

diamond or CBN is used.

The feature of this processing method is that high precision high efficiency honing is easy for

blind holes or discontinuous holes.

For short chips of cast iron, very economical processing is possible, whereas for long chips

like mild steel and hard steel, or streaky adhesive chips such as bronze and aluminum,

electric Processing is not easy because the surface of the wearing tool tends to be clogged.

Furthermore, in this processing, attempts have been made to commercialize emulsion type

water-soluble oils from the necessity of lubricity and cooling properties. Further, this

processing method has a need for an automated line or a robotized machine because it is

easy to standardize at a high level in terms of process control.

1.6.10 Honing processing of fine ceramics

We will describe the machinability of various fine ceramics with honing process, the

performance of grindstone use and the selection of whetstone.

(1) Machinability of fine ceramics

Table 16.19 shows the characteristic values of various fine ceramics. That is, borosilicate

glass (SiO2), alumina (Al2 O3), silicon carbide (SiC), and two different types of silicon nitride

(Si3N4) of the same manufacturer under the same pressureless sintering method. Then,

these materials were honed, and from the detailed study results, the experimental result on

the machinability using the private grinding stone shown in Table 16.20, which was deemed

appropriate for each, is shown in Figure 16.45.

In other words, the abscissa shows the grindstone depth of cut d when one grinding stone is

regarded as one cutting tool and the ordinate shows the specific cutting resistance K 2

(GPa) and chip volume of unit volume the energy Ks (J /mm3) required for generation is

shown.

The material at the lower right in this figure has better machinability.

SiO 2 and Al 2 O 3 are better machinability than spheroidal graphite cast iron (FCD 50)

processed as a comparison, and SiC and Si3N4 are bad.

(2) Wheel finish performance

Figure 16.46 shows the effect of abrasive grain size on the processing of Al2O3 and Si3 N4.

When the particle size number is large and the abrasive particle diameter becomes small,

the specific cutting resistance becomes large, the cutting depth and the finishing ratio

become small, and the machinability of the grindstone deteriorates.

The finished surface roughness improves rapidly with finer grain size, and mirror surface

can be obtained by processing Si3N4 with # 1200 grindstone.

Figure 16.47 shows the machined surface profile for the case in Figure 16.46.

(3) Grindstone selection

In the grinding wheel specification table 16.20 selected for each kind of fine ceramics,

abrasive grain type is preferably high toughness among diamonds, and the bonding

agent is more suitable for resin bond or vitrified bond than metal bond with large

abrasive grain support power.

When using the FCD50 material in metal processing as a reference, the concentration

should be higher for Al2O3 and SiO2, better for machinability, and low enough for SiC

and Si3N4 with poor machinability. Regarding the grindstone strength бb, a range of бb

= 80 to 150 MPa, which is smaller than that of metal working, is appropriate for a fine

ceramic material, and бb is made smaller for a material with poor machinability so as to

improve machinability It is necessary to select emphasized metal bond.

1.6.11 Troubleshooting in honing processing

Troubles that occur at the site honing process often have duplicate causes. Therefore,

detailed analysis and examination are required.

Table 16.21 shows troubleshooting on honing accuracy. Tables 16.22 and 16.23 show

troubleshooting on honing finishing performance and superabrasive grinding wheels

when super abrasive grains such as diamond or CBN are used.

Table16 .21 Honing Troubleshooting -Processing precision-

Decrease concentrations ○ ○ ○ ○

Decrease granularity ○

Use a hard grindstone ○

Use a sharp grinding stone ○ ○ ○ ○

○

Sizin

g equ

ipment (plu

ggau

ge type

)

Check eccentricity between pluggauge and honing tool or honing

head

○

Increase pushing pressure ofplug gauge

○

Check plug gauge expansion

Honin

g conditio

nFixtu

re

○

○Increase over travel

Do well motion ○

○○

○ ○

○ ○ ○ ○

○

○

○

○

○

○

○

○

○

○

○ ○

○ ○

○

○

Check the rigidity of the honinghead and the guide wear

Right angle of pre-machinedshape

Change to flange mounting

○

Unstable

Straigh

tness is

difficult to

achie

ve

Variatio

n in

finish

ed dim

ensio

ns

Roundness Cylindrical degree AngleStraight

nessSize

Decrease cutting speed

○

The bo

ttom

is finish

ed

small be

cau

se o

f the blin

d

hole

Fau

lt in stac

k honin

g

Failu

re o

f the lan

d width

Unstable

To be

elliptic

al

Degradatio

nby sag in

notc

hed part

Uneve

n fin

ish o

fth

e w

hole

circ

um

fere

nce

Both

ends be

com

e large

r

Both

ends be

com

e sm

all

mac

hin

eW

ork

piece

Check centering accuracy of tool and workpiece

Check the universal movementof the tool

Devise a tool layout

Correctly match the angle and

pitch of the expansion cone and thewheel head

Reduce the gap between the wheel

head and the groove of the honinghead

Check fluctuation of strokeposition

Supe

r-abrasive

grindin

g stone

Increase rotation speed

Increase run-out

Reduce over travel

○

Support reinforcement againstlack of rigidity of workpieces

Provide a work guide for the tool toprevent movement of the

workpiece

Improve fitting squareness

Stabilize the mountingreference surface

○

Increase Concentration ○

○ ○

Use a mold type grindstone ○

○

Lengthen the grindstone length ○ ○

The precision of the shape of thegrinding wheel does not come out

○

○

Control to constanttemperature

○

Replace with appropriate oil ○

Honin

g oil

Change to flange mounting ○

Shorten the grindstone length ○ ○

Increase the grindstone width ○

Measures

Trouble

Table16 .22 Honing Troubleshooting -Honing finish performance-

○ ○ ○ ○ ○

○ ○ ○ ○ ○ ○ ○ ○

○ ○ ○ ○

○ ○ ○ ○ ○ ○ ○ ○ ○

○ ○ ○ ○ ○ ○ ○ ○ ○ ○

○ ○ ○ ○ ○If the efficiency is high, theprocessing accuracy will be

deteriorated

Too good

Too rough

Unstable

Scratches on the machined surface

Bad sharpness and long cycle time

Incre

asing c

uttin

g speed

Decre

asing c

uttin

g speed

Incre

asing ro

tation spe

ed

Decre

asing ro

tation spe

ed

Incre

asing h

onin

g speed

Incre

asing ru

n-out tim

e

Usin

g soft grin

dingsto

ne

Usin

g hard grin

dingsto

ne

Incre

asing gran

ularity

Decre

asing gran

ularity

Honin

geffic

iency

Super grain grindingstone

Checkin

g oil de

terio

ration

Checkin

g filtration o

f oil

Rese

lectin

g the o

il

Honing oil

Decre

aasing c

oncentratio

n

Chan

ging abrasive

from

diamond to

CB

N

Chan

ging th

e type

of abrasive

Usin

g mold type

Chan

ging to

high

viscosity

Honing condition

Fin

ising

surfac

e

Incre

asing c

oncentratio

n

Usin

g 2 ste

p honin

gTrouble

Measures

Table16.23 Honing Troubleshooting -Super grain grindingstone-

Trouble Cause

Clogging

Grain flatten

Grindingstone does not fit

Insufficient dressing of grains

Increasing granularity, Using soft grindingstone, Decreasing concentration.

Decreasing cutting speed, Increasing or Decreasing rotation speed

Supplying enough oil to the processed surface, Using washable oil

Reduce the grindstone width

Making a sufficient chip space on the grindstone working surface by dressing

measures

Grindingstone does not fit

Processing conditions do not match

Fault of honing oil

Too wide grindingstone width

Processing conditions do not match

Fault of honing oil

Using soft gridingstone,Decreasing concentration,Changing abrasive from diamond to CBN

Decreasing or increasing cutting speed, Increasing or Decreasing rotation speed

Supplying enough oil to the processed surface, Using lubricating oil

Short life ofgrindingsotne

Grindingstone does not fit

Chipped grindingstone

Fault of honing oil

Using hard grindingstone,Increasing concentration, Using larger grindingstone

Decreasing concentration, Using fine granularity, Using Metal mold type,Using plastic moldtype,Using lubricating oil

Removing chips and grind stone powder in oil to clean