threads and ?

[normks]

ok i have a old enco lathe, i can change gears and get metric threads but it doesnt offer 1.25 mm it has 1.2 and 1.3 and the question of the day is 1.25 mm threads the same as 20 tpi ? i know i can cut this thanks for the help

 

[Tony Wells]

It's actually 20.32 TPI. Every inch of thread, you would lose about a third of a turn. If your thread were short, and a loose class, you could probably get by with it, but understand that it would not have optimum strength