Mechanical Engineering - Production Engineering - Discussion

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.

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?

What in the world is a negative relief angle?

Does it mean the tool will interfere in to the workpiece? I don't think negative relief is possible. Also, if they are talking about rake angle then why would soft workpiece require negative rake? If it is a rake. Then please someone explains the concept of negative rake on soft materials.

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.

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.

Rake angle will be POsitive as the workpiece is soft and RELIEF angle will negative means below ZERO ANGLE LINE (X-AXIS). Here, negative means sign convention not actual value.

The negative insert has an angle of 90° (0° clearance angle), while a positive insert has an angle of less than 90° (for example, 7° clearance angle).

This is the first time am hearing negative relief angle. I think it is a negative rake angle. And the negative rake angle is used when machining hard materials.

I think -ve rake angle is given for machining of high strength materials. And -ve relief angle does not even make sense. Does -ve relief angle even exists?

Relief Angle can not be negative. It is always positive in any condition to minimise rubbing between flank and work surface.