5.6 TOOL WEAR
Tool wear is still a significant problem in cutting.
Typical types of tool wear include,
Flank wear - the point of the tool degrades
Crater wear also decreases tool life
Tool failure can typically grouped under one of the following categories,
- Complete Failure - the tool is unusable
- Flank Failure - this can be estimated with maximum l
w values,
0.06" for high speed steel
0.015" for high speed steel
- Work surface finish is inadequate
- Work dimension outside tolerance
Flank wear can be discussed as a function of time,
General notes of concern are,
- The main factor in tool wear is temperature
- The main factor in tool life is cutting speed
- Critical temperatures for High Speed Steels are 1150°F and for carbides it is 1600°F
- A higher velocity will increase temperature more than an increase in feed for the same mrr
- A higher feed will increase the tool forces
