View Full Version : Four start threading using Mach2 ?

02-11-2004, 08:32 PM
Here is a tool for use in reloading firearm shells. It has a four-start thread. The collector of these old tools needs to have a copy made of this threaded tool. The handle and swivel parts can be made conventionally.
I would like to use Mach2's threading capability, and am installing a sensor on the lathe spindle to signal Mach2 of its position and speed. Will Mach2 be able to be set up to make four starts for this thread?

02-11-2004, 08:48 PM
I don't know if Mach2 would be limited by anything in particular. Simply cut each thread as if it were a stand alone process. When you are ready to begin the next thread start, reposition your tool at a new Z position that is 1/4 of the lead ahead (or back) of the position you began the first thread at. Then, run the entire thread cycle again. Repeat until complete, for each start, moving your start point by 1/4 of the lead for each thread start.

Important note: do not change spindle speeds throughout the entire cycle, on a cnc

You can also use this method on a manual lathe, using the cross slide to advance the tool for each unique thread start.

Good luck :)

02-11-2004, 09:09 PM
Thanks Huffed,
I didn't even consider the manual threading ... I have the shoptask 3 in 1 and although workable, the threading feature on this machine is quite awkward to work. But since it has CNC with Mach2 and is quite responsive with servos, I would like to do this for the collector as a learning process.
Now, that 1/4 turn you talk of..... would this "offset" so to speak be done all by Mach2? Would I tell Mach2 to adjust 90 degrees for the next thread..and so on?
Thanks again!

P.S. I would like to add that the collector, my brother, has one complete set of the tool as ahown, but is missing the insert for the accompaning receiver.

02-11-2004, 09:31 PM
I guess maybe I'm making this more complex than it really is....
I was thinking maybe I needed an indexer(4th axis) and whatever.
But now, it appears that with Mach2 I will be able to prepare g-code to run the whole process of four threads at once.
Experimentation is required here for the number of passes, types of passes, adjustment for next thread start, and on through the whole shabang! exciting! Got to get off this keyboard and make that infrared sensor mount.

02-11-2004, 10:04 PM
Yes, it is nothing to the cnc to do this. It is all a matter of the starting position, although it does require perfect repeatability of your machine's servos to act in exactly the same manner at all times when the pulse is received.

Maybe run a single thread or two first, to see how it behaves, though :D

You'll also have to pay special attention to the front and rear clearance angle of your toolbit. This would be a good place for a plain old HSS toolbit, where you can grind the rather excessive looking clearance angles.

02-11-2004, 10:23 PM
yes... I was examining those threads trying to determine if they were made that way or if they were rolled over a bit from constant use under pressure. Sure! some trial and error in making a custom bit to conform to the existing threads. Boy! the things one can learn from one small project!

You know, Huff, they say a good teacher leaves little doubt in the student.....You've removed that doubt from me!

02-11-2004, 11:57 PM
You know, Huff, they say a good teacher leaves little doubt in the student.....You've removed that doubt from me!

Hu is good, I agree Bloy2004, and I like your work as well.

Hu's quote is
B]First you get good and then you get fast.[/B]
It aint bragging when it's a fact.;)