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Milan cutting%20tools[1]
- 1. Objectives Usethe 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 29-1
- 2. 29-2 Cutting Tools Oneof 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
- 3. Cutting-Tool Materials Lathe toolbits generally made of five materials High-speed steel Cast alloys (such as stellite) Cemented carbides Ceramics Cermets More exotic finding wide use Borazon and polycrystalline diamond 29-3
- 4. Diamond Toolbits Used mainly to machine nonferrous metals and abrasive nonmetallics Single-crystal natural diamonds High-wear but low shock-resistant factors Polycrystalline diamonds Tiny manufactured diamonds fused together and bonded to suitable carbide substrate 29-4
- 5. 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 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 29-5
- 6. Cutting-Tool Nomenclature Nose radius: radius to which nose is ground Size 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 29-6
- 7. Lathe Toolbit Anglesand Clearances 29-7
- 8. Lathe Cutting-tool Angles Negative rake: face Positive rake: point of cutting tool and cutting edge contacts metal first and chip first and contact metal moves chip up the down the face of moves face of the toolbit the toolbit Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 29-8
- 9. Tool Life Crater wear occurs as result of chips sliding along When flank wear chip-tool interface, is .015 to .030 in. result of built-up need to be reground edge on cutting tool Occurs on side of cutting edge as result of friction Nose wear occurs between side of cutting-tool as result of friction between edge and metal being nose and metal being machined machined Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 29-9
- 10. Factors Affecting theLife 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
- 11. Turning Assume cutting machine steel: If rake and relief clearance angles correct and proper speed and feed used, a continuous chip should be formed. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 29-11
- 12. Nomenclature of aPlain Milling Cutter 29-12
- 13. Nomenclature of an End Mill Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 29-13
- 14. Characteristics of aGood Cutting Fluid 1. Good cooling 6. Rust capacity resistance 2. Good lubricating 7. Nontoxic qualities 8. Transparent 3. Resistance to rancidity 9. Nonflammable 4. Relatively low viscosity 5. Stability (long life) 34-14
- 15. Functions of aCutting Fluid Prime functions Provide cooling Provide lubrication Other functions Prolong cutting-tool life Provide rust control Resist rancidity 34-15
- 16. Milling Face milling Ring-type distributor recommended to flood cutter completely Keeps 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 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 34-16
Editor's Notes
- #8 The side cutting edge angle is the angle the cutting edge forms with the side of the tool shank (Fig. 29-4). Side cutting angles for a general-purpose lathe cutting tool may vary from 10° to 20°, depending on the material cut. If this angle is too large (over 30°), the tool will tend to chatter. The end cutting edge angle is the angle formed by the end cutting edge and a line at right angles to the centerline of the toolbit (Fig. 29-4). This angle may vary from 5° to 30°, depending on the type of cut and finish desired. An angle of 5° to 15° is satisfactory for roughing cuts; angles between 15° and 30° are used for general-purpose turning tools. The larger angle permits the cutting tool to be swiveled to the left for taking light cuts close to the dog or chuck, or when turning to a shoulder. The side relief (clearance) angle is the angle ground on the flank of the tool below the cutting edge (Figs. 29-4 and 29-5). This angle is generally 6° to 10°. The side clearance on a toolbit permits the cutting tool to advance lengthwise into the rotating work and prevents the flank from rubbing against the workpiece. The end relief (clearance) angle is the angle ground below the nose of the toolbit, which permits the cutting tool to be fed into the work. It is generally 10° to 15° for general-purpose tools (Figs. 29-4 and 29-5). This angle must be measured when the toolbit is held in the toolholder. The end relief angle varies with the hardness and type of material and the type of cut. The end relief angle is smaller for harder materials, providing support under the cutting edge. The side rake angle is the angle at which the face is ground away from the cutting edge. For general-purpose toolbits, the side rake is generally 14° (Figs. 29-4 and 29-5). Side rake creates a keener cutting edge and allows the chips to flow away quickly. For softer materials, the side rake angle is generally increased. Side rake may be either positive or negative, depending on the material being cut. The angle of keennes s is the included angle produced by grinding side rake and side clearance on a toolbit (Fig. 29-4). This angle may be altered, depending on the type of material machined, and will be greater (closer to 90°) for harder materials. The back (top) rake angle is the backward slope of the tool face away from the nose. The back rake angle is generally about 20° and is provided for in the toolholder (Fig. 29-5). Back rake permits the chips to flow away from the point of the cutting tool. Two types of back or top rake angles are provided on cutting tools and are always found on the top of the toolbit: > Positive rake (Fig. 29-6a), where the point of the cutting tool and the cutting edge contact metal first and the chip moves down the face of the toolbit > Negative rake (Fig. 29-6b), where the face of the cutting tool contacts the metal first and the chip is forced up the face of the toolbit