Manufacturing And Production Technology MCQ Questions & Answers | Mechanical Engineering

The relief angle, also known as the clearance angle, is a crucial angle in cutting tools like those made of high-speed steel (HSS).

Why is it important?
Imagine a tool cutting into material. If the flank (the side just behind the cutting edge) rubs against the workpiece, it creates friction and heat.
The relief angle prevents this rubbing.
It provides clearance between the flank and the machined surface.

What does it do?
Reducing friction, which then reduces heat and wear on the tool.
Leading to a better surface finish on the workpiece.
Allowing the tool to cut more efficiently.

How much relief angle is needed?
Too little relief angle and you get rubbing (bad!).
Too much and the cutting edge becomes weak and might chip or break.

Typical Values:
For HSS tools, the relief angles are generally kept relatively small to maintain the strength of the cutting edge.
The most common range for relief angles on HSS tools is 3° to 10°.

Therefore, the correct answer is Option B: 3° to 10°

The correct option is "Produces chipping and decreases tool life" (Option C).

The side cutting edge angle (SCEA) influences how the cutting force is distributed along the tool edge.

When SCEA is larger than 15°, the cutting edge becomes weaker because a longer portion of the edge is engaged in cutting. This reduces its strength, increases the chance of edge chipping, and ultimately decreases tool life.

Why not the others?

"Increases tool life" can be true up to a certain optimum angle, but beyond 15° the edge weakens and tool life reduces.

"Decreases tool life" is incomplete because the main reason is chipping due to weakening of the cutting edge.

"Results in excessive stress concentration and greater heat generation" is not the direct effect of a large SCEA; the main drawback is weakening of the edge.

Therefore, for exam purposes, the correct answer is Produces chipping and decreases tool life.