Multi start thread questions

[turnworks]

Changing a design to a 2 start thread 16tpi instead of the normal single start.

I couldn't figure out how to code in the lathe by hand. Its a 90's siemens controller and threading is L97, L971 ect. So I just used a little windows based wizard that spit out the G code for the thread I was wanting and uploaded it to the lathe and it ran fine.

While I was running the parts I went through the G code and I'm not understand how the code is telling the control to make 2 starts 180 degrees apart.

The code is dead simple G33 Z-.500 K0.125 There is nothing different from cutting the first thread to the second expect that the Z start location goes back to the start before descending each pass until final thread depth just like the first thread it cut. Meaning I could have just used a G33 code for 8tpi and then copy and pasted it right under itself and it would do a 2 start.

Parts are coming out just fine and I probably should even be thinking about how it works but now its in my head and I can't figure it out.

I'm sure someone knows so if you get time to explain it please do.

 

[turnworks]

Disregard post. I didn't look at the code close enough. The starting Z point is different for each thread making the start of the thread change locations. Hope at least someone gets a laugh from this.

 

[706jim]

Yup same idea as drawing one with Catia.

 

[MaxPrairie]

Disregard post. I didn't look at the code close enough. The starting Z point is different for each thread making the start of the thread change locations. Hope at least someone gets a laugh from this.

As I was reading I was thinking the start z would be different by 1/16