I've managed to cut 4 nice threads with my lathe. The metric one required reversing the motor and keeping the half nut engaged but the rest were all cut the easy way, half nut disengaged, carriage rolled back, re-engage half nut for next pass.
I have been able to engage on any of the 4 marks on the thread wheel and have cut 13, 20, and 32 TPI.
For each new TPI I cut, I have to assume it's necessary to engage on a particular mark, they are numbered 1-4 so there must be a reason. Makes for some time wasting and frustration.
I've tried to work out the math but I'm not getting anywhere.
For one chuck rotation the 1st change gear shaft rotates 90 degrees.
The lead screw is an oddball 7 TPI.
28 rotations of the leadscrew turn the thread wheel 360 degrees.
I think my thread constant is .03571428571 which I got by .25*(1/7).
Is there an easy way to determine which TPI can be engaged on any mark?
Since (1/thread constant) = 28 does that mean I can cut 14, 28, and 56 TPI by engaging anywhere without regards to the thread wheel?
I'm pretty sure I'm missing something very simple and I'd like to know what it is!