A question about thread.
 

Hi Everyone,

Please, I need help.

Please, can anyone tell me why:

Why do we have a different number of tooth worm
wheels on a metric lathe screw cutting and only one on
imperial lathe ?

A metric machine we have several worm wheel cover
the range of thread, on a imperial lather we only have
one, why ?

Thanks

Richard.

It does,but no one bothers with it.