4 Tool Materials

8/11/2019 4 Tool Materials

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Cutting Tools

One of most important components in machining process

Performance will determine efficiency of operation

Two basic types (excluding abrasives)

Single point and multiple point

Must have rake and clearance angles ground or formed

on them


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Cutting Tool Properties

Hardness Cutting tool material must be 1 1/2 times harder than the

material it is being used to machine.

Capable of maintaining a red hardness during

machining operation

Red hardness: ability of cutting tool to maintain sharp cutting

edge

Also referred to as hot hardness or hot strength


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Cutting Tool Properties

Wear Resistance Able to maintain sharpened edge throughout the cutting

operation

Same as abrasive resistance

Shock Resistance

Able to take the cutting loads and forces

Shape and Configuration

Must be available for use in different sizes and shapes


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Evolution of Tooling Materials


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High-Speed Steel

May contain combinations of tungsten, chromium,vanadium, molybdenum, cobalt

Can take heavy cuts, withstand shock and maintain

sharp cutting edge under red heat

Generally two types (general purpose) Molybdenum-base (Group M)

Tungsten-base (Group T)

Cobalt added if more red hardness desired


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Cast Alloy

Usually contain 25% to 35% chromium, 4% to 25% tungsteand 1% to 3% carbon

Remainder cobalt

Qualities

High hardness High resistance to wear

Excellent red-hardness

Operate 2 times speed of high-speed steel

Weaker and more brittle than high-speed steel


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Carbide Cutting Tools

First used in Germany during WW II as substitute fordiamonds

Various types of cemented (sintered) carbidesdeveloped to suit different materials and machiningoperations

Good wear resistance Operate at speeds ranging 150 to 1200 sf/min

Can machine metals at speeds that cause cuttingedge to become red hot without loosing harness


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Tool Life in Steel

High Speed Steel

Solid Carbide

TiN Coated

TiCN Coated

AlTiN ( TiAlN )

Tool Life

Cost

Higher

Lower


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Solid Carbide vs. High Speed Steel

HSS = 58-62 Rc (approx.80-82 Ra)

Solid Carbide = 89-94 Ra

Increase in Hardness Provides:

Use Higher Speed and Feeds

Longer Lasting Cutting Edges

Carbide Retains Hardness at Elevated Temperatures


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Carbide Grades

Carbide is a Composite ( WC )

Tungsten Carbide Particle Sizes: From 0.4 um to 1.2 um

Different Percentages of Cobalt Used as a Binder Material


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Effect of Grain Size on Carbide Properties

As grain size decreases:

Hardness increases

Impact strength may decrease

Edge strength increase

As grain size increases:

Hardness decreases

Impact strength may increase

Edge strength decrease

10% Cobalt ( Co )

0.6 umTungsten Carbide ( WC )

grain size

10% Cobalt ( Co )

1.2 umTungsten Carbide ( WC )

grain size

WC WC

WCWC

WCWC

WCWC

WC

WCWC

Co

WC

Co WC

WC

WC


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Effect of Cobalt % on Carbide Properties

As Cobalt % decreases:

Hardness increases

Impact strength decrease Stiffness increase

As Cobalt % increases:

Hardness decreases

Impact strength increase

Stiffness decrease

10%Cobalt ( Co )

0.6 um Tungsten Carbide ( WC )

grain size

15%Cobalt ( Co )

0.6 um Tungsten Carbide ( WC

grain size

WC WC

WC

WC

WCWC

WC

WC

WC

WCWC

Co

WCWC

WC

WCWC

WC

WCWC

Co


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Grade Selection

As Cobalt 6 %and

1.3~1.5 umGrain Size

Non - Ferrous or

Non - Metal

As Cobalt 10 %and

0.8 umGrain Size

Ferrous or

Long Reach

As Cobalt 14~16 % and

0.8 um Grain Size

Tougher Ferrous


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Tool Coatings

More Application Specific Coatings Available :

TiN ( Titanium Nitride )

TiCN (Titanium Carbon Nitride )

TiAiN (Titanium Aluminum Nitride )

Diamond


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Tool Coatings Provide

Cutting Edge Protection

Added Lubricity

Higher Cutting Speeds Not all Carbide Grades are compatible with all tool coatings

Strict cleaning and handling procedures required


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Tool Coatings are NOT a substitute for: -

Improper Geometry for an Application

Poor Quality Tools

Improper Carbide Grade for an Application


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Tool Material and Coatings

( Micro-Grain Carbide )

Applications & Benefits: General Purpose Use

Wide range of materials

High feeds & speeds

Micro-Grain Carbide : Color Gray

Micro hardness 2000 Vickers

(Approx.. 70-75 Rockwell C)


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Tool Material and Coatings ( TiN )

Applications & Benefits: General Purpose Use

Wide range of materials

3 to 8 times longer tool life than carbide

Higher feeds & speedsTitanium Nitride ( TiN ) : Color Gold / Yellow

Film Thickness 1- 5 Microns

Microhardness 2300 Vickers

( Approx. 80-85 Rockwell C )


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Tool Material and Coatings ( TiCN )

Applications and Benefits :

High Performance Applications

Difficult to machine materials

Higher speeds and feeds possible for enhanced machiningproductivity

Wear resistance and toughness superior to TiN

High speed machining

Materials up to 40 ~ 50 Hrc


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Tool Material and Coatings ( TiCN )

Titanium Carbonitride ( TiCN )

Color :- Blue / Gray



(Approx. 90 Rockwell C)


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Applications and Benefits :

High Performance Applications

Difficult to machine materials

Higher speeds and feeds possible for enhanced machining productivity

Wear and heat resistance superior to TiAlN

High speed machining

Hardened Materials to 60 HRc

Tool Material and Coatings ( TiAlN )


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Aluminum Titanium Nitride (TiAlN)

Color : Purplish / Black



(Approx. 95 Rockwell C)

Tool Material and Coatings ( TiAlN )


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Applications & Benefits: General Purpose Use Use for non-ferrous materials (aluminum and graphite)

15 times longer tool life than TiN coated tools

Higher feeds & speeds

COATING Diamond : Color : - Black

Film Thickness 10 Microns


(Approx. 90-95 Rockwell C)

Tool Material and Coatings ( Diamond )


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Coatings for hardened material

H.S.S High Spees Steel 30 HRC

W.C Micro grain carbide 40 HRC

TiN Titanium Nitride 40 HRC

TiCN Titanium Carbon Nitride 45 ~ 50 HRC

TiAlN Titanium Aluminum Nitride 50 ~ 62 HRC


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A lternat ives to Carb ide

Compared to carbide, the materials listed here tend to offer

higher hardness (including hot hardness) but lower

toughness. Whether or not any one of these tools can justify

its cost premium over carbide will vary from application to

application. Find the right cutting tool by testing various

alternatives in your process.


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Ceramic:

Ceramics used to mill and drill cast iron are silicon

nitride based. They are effective in machining gray

cast iron, and often deliver more tool life as speeds

increase. In fact, ceramics generally should not berun at speeds lower than 650 sfpm. In drilling,

ceramic tools are at their most effective in holes no

more than 4 diameters deep.


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Cermet :

Cermet (CERamic METal) consists of ceramicparticles in a metal binder. Cermet tools can be used

in both cast iron and cast aluminum, as well as in

many other materials. In milling, cermet is typically

thought of as a finishing tool because it can oftenproduce surface finishes superior to what carbide

can achieve. However, cermet milling cutters can

also stand up to heavier cuts.


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CBN & PCD:

CBN (Cubic Boron Nitride) and PCD

(Polycrystalline Diamond) are expensive tool

materials, but in certain high speed machining

applications they can deliver long tool life, as

in the part shown below. CBN and PCD are

applied either as coatings to solid tools or on

the tips of inserts. CBN is used for ferrous

applications, PCD for non-ferrous.


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Manufacturing of CBN/PCD Inserts


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Protect Against Shocks

Ceramic, cermet, CBN, and

PCD are all more likely than

carbide to chip or crack as a

result

of vibration or thermal shock.


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Hot hardness characteristics of engineering tool material

f


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Hardness vs. toughness for various cutting materials

S d V F d S it bilit


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Speed Vs Feed -Suitability

4 Tool Materials

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