Mechanical Engineering - Production Engineering - Discussion

What purpose used to negative rake angles?

I think this angles used to machining the hard materials only.

What is negative relief angle? I think it must be negative rake angle and is provided while machining high strength alloys.

Relief angles are for the purpose of helping to eliminate tool breakage and to increase tool life. The included angle under the cutting edge must be made as large as practical. If the relief angle is too large, the cutting tool may chip or break. If the angle is too small, the tool will rub against the work piece and generate excessive heat, and this will in turn, cause premature dulling of the cutting tool.

Small relief angles are essential when machining hard and strong materials, and they should be increased for the weaker and softer materials. A smaller angle should be used for interrupted cuts or heavy feeds, and a larger angle for semi-finish and finish cuts.

It is used for hard materials and for material having high rigidity. Positive rake angle means pointed tool so it will not be able to withstand larger fores and more tool wear while the power consumption will be lower. For negative rake angle the tools are blunt and they can withstand higher forces and used for hard materials.

Relief angle never negative. It lie between 3-15 degree.

The answer should be rake angle.

- It makes the tool blunter, increasing the strength of the cutting edge.

The answer is wrong.

It should be rake angle.

Negative rake only used for hard metals. But negative relief angle used for soft metals.

Goodmorning! I was reading about thermal spray coating properties (ASM, 2004) and it is mentioned that "Substrate asperities with negative relief can be formed prior to coating by grit blasting and other mechanical surface preparation techniques". So looking at the answers above "negative relief" is an angle or it can also be something else? if it can what is it? can someone recommend an enlightening article?