Milan cutting%20tools[1]

Objectives

Use the nomenclature of a cutting-tool point

Explain the purpose of each type of rake and clearance angle

Identify the applications of various types of cutting-tool materials

Describe the cutting action of different types of machines

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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 multi point

Must have rake and clearance angles ground or formed on them

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Cutting-Tool Materials

Lathe toolbits generally made of five materialsHigh-speed steelCast alloys (such as stellite)Cemented carbidesCeramicsCermets

More exotic finding wide useBorazon and polycrystalline diamond

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Diamond Toolbits

Used mainly to machine nonferrous metals and abrasive nonmetallics

Single-crystal natural diamondsHigh-wear but low shock-resistant factors

Polycrystalline diamondsTiny manufactured diamonds fused together

and bonded to suitable carbide substrate

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Cutting-Tool Nomenclature

Cutting edge: leading edge of that does cutting

Face: surface against which chip bears as it is separated from work

Nose: Tip of cutting tool formed by junction of cutting edge and front face

29-5Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Cutting-Tool Nomenclature

Nose radius: radius to which nose is groundSize of radius will affect finish

○ Rough turning: small nose radius (.015in)○ Finish cuts: larger radius (.060 to .125 in.)

Point: end of tool that has been ground for cutting purposes

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Lathe Toolbit Angles and Clearances

29-7

Lathe Cutting-tool Angles

29-8

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Positive rake: point of cutting tool and cutting edgecontact metal first and chipmoves down the face ofthe toolbit

Negative rake: face of cutting tool contacts metal first and chip moves up the face of the toolbit

Tool Life

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Occurs on side of cuttingedge as result of friction

between side of cutting-tooledge and metal being

machined

When flank wear is .015 to .030 in.need to be reground

Nose wear occursas result of friction betweennose and metal being machined

Crater wear occurs as resultof chips sliding along chip-tool interface,result of built-upedge on cuttingtool

Factors Affecting the Life of a Cutting Tool

Type of material being cut Microstructure of material Hardness of material Type of surface on metal (smooth or scaly) Material of cutting tool Profile of cutting tool Type of machining operation being performed Speed, feed, and depth of cut

29-10

Turning

29-11

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Assume cutting machine steel: If rake and relief clearanceangles correct and proper speed and feed used, a continuouschip should be formed.

29-12

Nomenclature of a Plain Milling Cutter

Nomenclature of an End Mill

29-13Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Characteristics of a Good Cutting Fluid

1. Good cooling capacity

2. Good lubricating qualities

3. Resistance to rancidity

4. Relatively low viscosity

5. Stability (long life)

6. Rust resistance

7. Nontoxic8. Transparent9. Nonflammable

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Functions of a Cutting Fluid

Prime functionsProvide coolingProvide lubrication

Other functionsProlong cutting-tool lifeProvide rust controlResist rancidity

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Milling

Face millingRing-type distributor recommended to flood

cutter completelyKeeps each tooth of cutter immersed in cutting

fluid at all times Slab milling

Fluid directing to both sides of cutter by fan-shaped nozzles ¾ width of cutter

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