Question

The double-threaded screw is made to rotate one complete rotation the screw advanced to 10 mm. Lead (pitch of helix) is given as 10 mm. The pitch of the screw is ____

(a) 10 mm

(b) 5 mm

(c) 1 mm

(d) 12 mm

The question was asked in an interview for job.

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

Answer 1

Correct option is (b) 5 mm

Explanation: In a double –threaded screw, the lead = the pitch of helix = 2 times of pitch of the screw. The pitch of screw = 10mm / 2 =5 mm. Even if the single- threaded screw is changed to double threaded screw the cross-section of thread and pitch of screw won’t change.