Question

When a double –threaded screw is made to turn 120 degrees about axis. How much the screw advances through axis?

(a) ^1⁄3 of pitch of helix

(b) ^1⁄3 of pitch of screw

(c) ^1⁄4 of pitch of helix

(d) The advancement is equal to pitch of helix.

I had been asked this question by my school principal while I was bunking the class.

This question is from Construction of Screw Threads topic in division Curves used in Engineering Practice of Engineering Drawing

Answer 1

Right option is (a) ^1⁄3 of pitch of helix

The best explanation: For a Double-threaded screw, Pitch of the helix = lead = Twice the pitch of the screw. 120 is ^1⁄3 part of 360 (complete rotation). So the lead advances to ^1⁄3 of pitch of helix and ^2⁄3 of pitch of screw.