Speed Threading on the Lathe

[thestelster]

Most of my threading is typically under 2" in length. I usually have to cut to a shoulder, so lathe speed is around 50rpm so I can disengage the half nuts and back out before hitting the shoulder.

Today I had to make a 1/2"-20 threaded shaft. The threaded portion is 4" long. At 50 rpm, I would have fallen asleep by the time it reached the end. Fortunately, I have a VFD which I've hooked up a potentiometer to control the spindle speed. So I set the pot to 10Hz (50rpm) to start the thread, then increased it to 60hz (300rpm), and then back to 10Hz about 1/2" before the end of the thread to disengage the half-nuts.

In this case, no shoulder, but I used the carriage indicator to disengage at zero.

 

[Susquatch]

Fortunately, I have a VFD which I've hooked up a potentiometer to control the spindle speed.

I cannot wait to convert mine. I have all the parts, just need to git er done!

 

[Proxule]

I cannot wait to convert mine. I have all the parts, just need to git er done!

Literally the first mod I did, and the one that brings me the most joy.
Wish you luck my friend!

 

[Susquatch]

Literally the first mod I did, and the one that brings me the most joy.
Wish you luck my friend!

Thanks, I'll need it. I'm combining the 3ph conversion, VFD, DRO, and taper attachment all in one go be cause each one affects the others........

But I need my lathe and use it at least twice a week. So I'll have to give up doing other stuff while I do the conversion.

 

[pdentrem]

I replaced the 1.5 hp cast iron motor with a 2 hp aluminum inverter rated motor and added the VFD. Makes the lathe much more adaptable to differing conditions. Best upgrade so far. I already had a QCTP from the old lathe.
Pierre