CHAPTER 21 · PDF fileCHAPTER 21 Cutting-Tool Materials and Cutting Fluids. ... Application of...

Kalpakjian • SchmidManufacturing Engineering and Technology © 2001 Prentice-Hall Page 21-1

CHAPTER 21

Cutting-Tool Materials and CuttingFluids

Kalpakjian • SchmidManufacturing Engineering and Technology © 2001 Prentice-Hall 1-2

Cutting Tool Material Hardnesses

Figure 21.1 The hardness of variouscutting-tool materials as a function oftemperature (hot hardness). The widerange in each group of materials is dueto the variety of tool compositions andtreatments available for that group. Seealso Table 21.1 for melting ordecomposition temperatures of thesematerials.


Typical Properties of Tool MaterialsTable 21.1

Carbides

PropertyHigh-speed

steels Cast alloys WC TiC CeramicsCubic boron

nitrideSingle-crystal

diamond*

Hardness 83– 86 HRA 82– 84 HRA 90– 95 HRA 91– 93 HRA 91– 95 HRA 4000– 5000 HK 7000– 8000 HK46– 62 HRC 1800– 2400 HK 1800– 3200 HK 2000– 3000 HK

Compressive strength MPa psi x10

34100– 4500600– 650

1500– 2300220– 335

4100– 5850600– 850

3100– 3850450– 560

2750– 4500400– 650

69001000

69001000

Transverse rupture strength MPa psi x10

32400– 4800350– 700

1380– 2050200– 300

1050– 2600150– 375

1380– 1900200– 275

345– 95050– 135

700105

1350200

Impact strength J in.- lb

1.35– 812– 70

0.34– 1.253– 11

0.34– 1.353– 12

0.79– 1.247– 11

< 0.1< 1

< 0.5< 5

< 0.2< 2

Modulus of elasticity GPa psi x10

620030

––

520– 69075– 100

310– 45045– 65

310– 41045– 60

850125

820– 1050120– 150

Density kg/m

3

lb/in.3

86000.31

8000– 87000.29– 0.31

10,000– 15,0000.36– 0.54

5500– 58000.2– 0.22

4000– 45000.14– 0.16

35000.13

35000.13

Volume of hard phase, % 7– 15 10– 20 70– 90 – 100 95 95Melting or decompositiontemperature °C °F

13002370

––

14002550

14002550

20003600

13002400

7001300

Thermal conductivity, W/m K

30– 50 – 42– 125 17 29 13 500– 2000

Coefficient of thermalexpansion, x10

–6 °C

12 – 4– 6.5 7.5– 9 6– 8.5 4.8 1.5– 4.8

*The values for polycrystalline diamond are generally lower, except impact strength, which is higher.


General Characteristics of Cutting-ToolMaterials

TABLE 21.2 General Characteristics of Cutting- Tool Materials. These Tool Materials Have a Wide Range ofCompositions and Properties; Thus Overlapping Characteristics Exist in Many Categories of Tool Materials.

Carbon andlow- to

medium- alloysteels

High speedsteels

Cast- cobaltalloys

Uncoatedcarbides

Coatedcarbides Ceramics

Polycrystallinecubic boron

nitride DiamondHot hardness IncreasingToughness IncreasingImpact strength IncreasingWear resistance IncreasingChippingresistance

Increasing

Cutting speed IncreasingThermal-shockresistance

Increasing

Tool material cost IncreasingDepth of cut Light to

mediumLight toheavy

Light toheavy

Light toheavy

Light toheavy

Light toheavy

Light to heavy Very light forsingle crystaldiamond

Finish obtainable Rough Rough Rough Good Good Very good Very good ExcellentMethod ofprocessing

Wrought Wrought,cast, HIP

*

sintering

Cast andHIPsintering

Coldpressingandsintering

CVD orPVD

†Coldpressingandsinteringor HIPsintering

High-pressure,high-temperaturesintering

High-pressure,high-temperaturesintering

Fabrication Machiningand grinding

Machiningandgrinding

Grinding Grinding Grinding Grinding andpolishing

Grinding andpolishing

Source : R. Komanduri, Kirk- Othmer Encyclopedia of Chemical Technology , (3d ed.). New York: Wiley, 1978.* Hot- isostatic pressing.†

Chemical- vapor deposition, physical- vapor deposition.


Operating Characteristics of Cutting-ToolMaterials

TABLE 21.3

Tool materials General characteristicsModes of tool wear or

failure LimitationsHigh-speed steels High toughness, resistance

to fracture, wide range ofroughing and finishingcuts, good for interruptedcuts

Flank wear, crater wear Low hot hardness, limitedhardenability, and limitedwear resistance

Uncoated carbides High hardness over a widerange of temperatures,toughness, wear resistance,versatile and wide range ofapplications

Flank wear, crater wear Cannot use at low speedbecause of cold welding ofchips and microchipping

Coated carbides Improved wear resistanceover uncoated carbides,better frictional andthermal properties

Flank wear, crater wear Cannot use at low speedbecause of cold welding ofchips and microchipping

Ceramics High hardness at elevatedtemperatures, high abrasivewear resistance

Depth-of-cut line notching,microchipping, grossfracture

Low strength, low thermo-mechanical fatigue strength

Polycrystalline cubicboron nitride (cBN)

High hot hardness,toughness, cutting-edgestrength

Depth-of-cut line notching,chipping, oxidation,graphitization

Low strength, lowchemical stability at highertemperature

Polycrystalline diamond Hardness and toughness,abrasive wear resistance

Chipping, oxidation,graphitization

Low strength, lowchemical stability at highertemperature

Source: After R. Komanduri and other sources.


Carbide Inserts

Figure 21.2 Typical carbide insertswith various shapes and chip-breakerfeatures; round inserts are alsoavailable (Fig. 21.4). The holes in theinserts are standardized forinterchangeability. Source: Courtesyof Kyocera Engineered Ceramics, Inc.,and Manufacturing EngineeringMagazine, Society of ManufacturingEngineers.


Insert Attachment

Figure 21.3 Methods of attaching inserts to toolholders: (a) Clamping, and (b) Wing lockpins. (c)Examples of inserts attached to toolholders with threadless lockpins, which are secured with sidescrews. Source: Courtesy of Valenite. (d) Insert brazed on a tool shank (see Section 30.2).

(a) (b)

(c) (d)


Edge Strength

Figure 21.4 Relative edgestrength and tendency forchipping and breaking ofinsets with various shapes.Strength refers to the cuttingedge shown by the includedangles. Source:Kennametal, Inc.

Figure 21.5 Edge preparation of insertsto improve edge strength. See alsoSection 23.2. Source: Kennametal, Inc.


Classification of Tungsten Carbides

Table 21.4 Classification of Tungsten Carbide According to Machining Applications. See also Chapters 22 and 23 for Cutting ToolRecommendations

Characteristics ofISO Standard ANSIClassification

Number

Materials to bemachined

MachiningOperation

Type of carbide

Cut Carbide

K30-K40 C-1 RoughingK20 C-2 General purposeK10 C-3 Light finishingK01 C-4

Cast iron,nonferrous metalsand nonmetallicmaterials requiringabrasion resistance

Precisionmachining

Wear-resistantgrades; generallystraight WC-Cowith varyinggrain sizes

Increasing Cuttingspeed

Increasing Feedrate

Increasinghardness and wear

resistance

Increasingstrength and

binder contentP30-P50 C-5 RoughingP20 C-6 General purposeP10 C-7 Light purposeP01 C-8

Steels and steelalloys requiringcrater anddeformationresistance

Precision finishing

Crater-resistantgrades; variousWC-Cocompositionswith TiC and/orTaC alloys

Increasing Cuttingspeed

Increasing Feedrate

Increasinghardness and wear

resistance

Increasingstrength and

binder contentNote: The ISO and ANSI comparisons are approximate.


ISO Classification of Carbide Cutting ToolsAccording to Use

TABLE 21.5

Symbol Workpiece material Color code

Designation in increasing orderof wear resistance and

decreasing order of toughness ineach category, in increments of 5

P Ferrous metals with long chips Blue P01, P05 through P50M Ferrous metals with long or short

chips; nonferrous metalsYellow M10 through M40

K Ferrous metals with short chips;nonferrous metals; nonmetallicmaterials

Red K01, K10 through K40


Effect of Coating Materials

Figure 21.6 Relative time required tomachine with various cutting-tool materials,indicating the year the tool materials wereintroduced. Source: Sandvik Coromant.


Multiphase CoatingsFigure 21.7 Multiphase coatings on a tungsten-carbide substrate. Threealternating layers of aluminum oxide are separated by very thin layers ottitanium nitride. Inserts with as many as thirteen layers of coatings have beenmade. Coating thicknesses are typically in the range of 2 to 10 µm. Source:Courtesy of Kennametal, Inc., and Manufacturing Engineering Magazine,Society of Manufacturing Engineers.


Properties for Groups of Tool Materials

Figure 21.8 Ranges of properties forvarious groups of tool materials. Seealso Tables 21.1 through 21.5.


Cubic Boron Nitride

Figure 21.9 Construction of a polycrystalline cubic boronnitride or a diamond layer on a tungsten-carbide insert.

Figure 21.10 Inserts with polycrystalline cubicboron nitride tips (top row) and solidpolycrystalline cBN inserts (bottom row).Source: Courtesy of Valenite.


Approximate Cost of Selected Cutting Tools

TABLE 21.6Tool Size (in.) Cost ($)High-speed steel tool bits 1/4 sq.x 2 1/2 long 1–2

1/2 sq. x 4 3–7Carbide-tipped (brazed) tools for turning 1/4 sq. 2

3/4 sq. 4Carbide inserts, square 3/16"thickPlain 1/2 inscribed circle 5–9Coated 6–10Ceramic inserts, square 1/2 inscribed circle 8–12Cubic boron nitride inserts, square 1/2 inscribed circle 60–90Diamond-coated inserts 1/2 inscribed circle 50–60Diamond-tipped inserts (polycrystalline) 1/2 inscribed circle 90–100 1


Application of Cutting Fluids

Figure 21.11 Schematic illustration ofproper methods of applying cuttingfluids in various machiningoperations: (a) turning, (b) milling, (c)thread grinding, and (d) drilling.

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