Question

At which part of the precision straight edge is generally lapped?

(a) Edges only

(b) Base only

(c) Base and edges both

(d) All over the surface

I have been asked this question in a job interview.

I want to ask this question from Straightness in division Straightness, Flatness, Squareness, Parallelism, Circularity and Rotation of Engineering Metrology

Answer 1

Correct answer is (a) Edges only

To elaborate: Straight edges are extremely useful for setting up machines such as planers. Precision straight edges are hardened and lapped on the edges by a small radius, which makes a blunt knife edge straight to a few thousands of an mm.