State why gear teeth have to be undercut.

Question

(i) State why gear teeth have to be undercut.                                                                      

(ii) The following data refers to two 20⁰C involute spur gears in mesh externally:

        Velocity ratio                         = 3

        Module                                  = 3 mm

        Addendum                             = 1.1 module

If the pinion rotates at 120 r.p.m. find –

(1)   the minimum number of teeth on each gear wheel to avoid interference:

Answer 1

(ii) Minimum no. of teeth to avoid interference between gears