| A | B |
|---|
| Chip breakers | are frequently used with single-point tools to force the chips to curl more tightly than they would naturally be inclined to do, thus causing them to fracture. |
| There are two principal forms of chip breaker design commonly used on single-point turning tools | (a) groove-type chip breaker designed into the cutting tool itself, and (b) obstruetion-type chip breaker designed as an additional device on the rake face of the tool |
| Effect of Tool Material on Tool Geometry | With the development of the very hard tool materials (e,g" cemented carbides and ceramics), changes in tool geometry were required, As a group, these materials have higher hardness and lower toughness than HSS,Also, their shear and tensile strengths are low relative to their compressive strengths, and their properties cannot be manipulated through heat treatment like those of HSS, Finally, cost per unit weight for these very hard materials is higher than the cost of HSS, These factors have affected cutting-tool design for the very hard tool materials in several ways. |
| First, the very hard materials must be designed with either (2) | negative rake or small positive angles, |
| Another difference is the way in which the cutting edge of the tool is held in position. i.e. inserts etc (just know) | Another difference is the way in which the cutting edge of the tool is held in position |
| Inserts | Cutting-tool inserts are widely used in machining because they are economical and adaptable to many different types of machining operations: turning, boring, threading, milling, and even drilling |
| edge preparation | Some kind of shape alteration is commonly performed on the cutting edge at an almost microscopie leveL |
| effect of edge preparation | The effect of this edge preparation is to increase the strength of the cutting edge by providing a more gradual transition between the clearance edge and the rake face of the tooL |
| Three common edge preparations are | (a) radius or edge rounding, also referred to as honed edge, (b) chamfer, and (e) land. |
| cutting fluid | is any liquid Or gas that is applied directly to the machining operation to improve cutting performance |
| Cutting fluids address two main problems: | (1) heat generation at the shear zone and friction zone, and (2) friction at the tool-chip and tool-work interfaces. |
| There are two general categories of cutting fluids, corresponding to the two main problems they are designed to address | coolants, and lubricants |
| coolants | are cutting fluids designed to reduce the effects of heat in the machining operation. They have a limited effect on the amount of heat energy generated in cutting; instead, they carry away the heat that is generated, thereby reducing the temperature of tool and workpiece. |
| Coolants do what? | prolong the life of the cutting tooL |
| Lubricants | are usually oil-based fluids (since oils possess good lubricating qualities) formulated to reduce friction at the tool-chip and tool-work interfaces |
| extreme pressure lubrication | Lubricant cutting fluids operate by extreme pressure lubrication, a special form of lubrication that involves formation of thin solid salt layers on the hot, clean metal surfaces through chemical reaction with the lubricant |
