Are there any tutorials on making threads on a lathe?
I have a converted CNC chineese lathe to running Mach 3. I can make threads that look like threads, but I'm a bit lost on making threads that are structurally correct and have the proper form.
When I take the diagrams and charts in the machinist handbook and try to make threads to the specified depths they always seem to shallow.
For example I want to make a 2 1/4" -20 UN thread both the internal and external thread.
From the thread tables... External 2.25 -20 Class 2A
Major diameter 2.2485 max to 2.2404 min
So step one would be to turn the area to be threaded is the shoulder to this dimension.
Next I have to actually cut the thread.... I'll use a form tool with 60 degree tip angle. then I cut 20TPI to a diameter of 2.1890 with a sharp v thread I get this from the UNR minor dia max.I'm not sure what to do with the Pitch diameter number???
Is this correct?
For the internal thread I first turn/bore the inside to between 2.196 and 2.207 Then I cut the threads at 20 TPI to a diameter of 2.250
Is this correct?
If I've done all of this how do I inspect my work? How do I go about measureing the thread depth etc....