Question

Chamfer is conical round off to the prism of bolt head at:

• A. an angle of $15^{\circ}$ on the outer end face.
• B. an angle of $30^{\circ}$ on the inner end face.
• C. an angle of $15^{\circ}$ on both end face.
• D. an angle of $30^{\circ}$ on the outer end face.

Hint:

The $30^{\circ}$ chamfer on the outer end face of a hexagonal nut or bolt head produces the characteristic hyperbolic arcs visible on the front and side views of the head.

Answer 1

The Correct Option is D

Step 1: Understanding Chamfering on Bolt Heads:
Chamfering is the process of removing sharp corners of a polygonal prism (such as a hexagonal or square bolt head). This conical cutting prevents injury during handling and facilitates easier engagement of tightening tools (spanners).

Step 2: Proportions and Angle of Chamfer:
For a standard hexagonal bolt head:
• The chamfering is done on the outer end face (the top-most flat surface of the bolt head, away from the shank).
• The chamfer is machined as a conical surface inclined at an angle of $30^{\circ$} to the flat top face of the bolt head.

Step 3: Conclusion:
This makes option (D) the mathematically correct and standard textbook statement.