Square Form thread

[djm77]

I was wondering if somebody could point me in the right direction for producing a square form thread on a Haas Lathe. We have an SL30 and a TL2. I have only ever produced a square form thread on a manual lathe and that is relatively easy to do as you can just wind the cross slide out. I am concerned that on the CNC the lead out is done at an angle.

It is an internal thread and it has an undercut groove at the back end of the thread which is the same width as the thread form. How do I get the machine to feed in in Z to the right depth and the just move in the X axis before returning to the start of the thread for the next path?

Thanks for any guidance on this.

[txcncman]

Regular G76 threading cycle will work just fine for this. Use M24 for Chamfering Off for straight pull out.

For chamfering (angle pull out):

At the end of the thread an optional chamfer is performed. The size and angle of the chamfer is controlled with Setting 95 (Thread Chamfer Size) and Setting 96 (Thread Chamfer Angle). The chamfer size is designated in number of threads, so that if 1.000 is recorded in Setting 95 and the feed rate is .05, then the chamfer will be .05. A chamfer can improve the appearance and functionality of threads that must be machined up to a shoulder. If relief is provided for at the end of the thread then the chamfer can be eliminated by specifying 0.000 for the chamfer size in Setting 95, or using M24. The default value for Setting 95 is 1.000 and the default angle for the thread (Setting 96) is 45 degrees.

[djm77]

I did read that in the manual but wasn't 100% certain about it.

Is it as simple as adding M24 to the G76 line to cause the tool to come out straight in X?

[txcncman]

I did read that in the manual but wasn't 100% certain about it.

Is it as simple as adding M24 to the G76 line to cause the tool to come out straight in X?

I would think the M24 would need to come before G76. I assume you want to use a grooving too to cut this type of thread. Be sure to add some relief angle on the tool slightly greater than the helix angle of the thread.

[Geof]

Use a slowish speed especially on the TL2 so the X movement is within the machines rapid limit. I do threading on a TL2 and find that often it cannot pull out quickly enough at the end of the thread.

[txcncman]

Use a slowish speed especially on the TL2 so the X movement is within the machines rapid limit. I do threading on a TL2 and find that often it cannot pull out quickly enough at the end of the thread.

This is a good point, but should not be an issue since the part has a thread relief groove the same dimension of the thread. It is a good practice to take this into consideration when threading to a shoulder.

[djm77]

It's not really a problem of how to do it or the ins and outs of relief on grooving tools etc, the problem was how to get the Haas lathe to move out in the single axis. I think you may be right about the M24 on the line before the G76. I think I will put an M23 on the line after also, to ensure there is no issue later on in life with other jobs. Not sure which machine it will be done on yet, it all depends on the qty.

[gizmo_454]

...I think I will put an M23 on the line after also, to ensure there is no issue later on in life with other jobs.

This is not really a necessity since it does not permanently change the setting. I don't know if it resets when the program hits M30, or if it happens when the machine is powered off. The default when the machine is powered on is with chamferring turned on.

Mike