Tap or internal threading tool advice

[maccrazy2]

Gentlemen. I am helping a friend out with a 12/36 jet lathe tailstock quill. The bushing striped out in the quill. I replaced the bushing already but need to cut the threads into it. There lies the issue. The rod is 14mm OD with 10 TPI acme style Left hand threads. It does not look quite like acme or square cut threads. I was going to try to grind a small internal threading tool but I’m beginning to think matching the profile may be easier if I cut external threads and make tap.

The material is brass and the hole is .850 deep. The threads are approximately.080 tall per side.

The ID of the hole is approximately.420

Any recommendations on how you would go at it?

[Cutter]

Gentlemen. I am helping a friend out with a 12/36 jet lathe tailstock quill. The bushing striped out in the quill. I replaced the bushing already but need to cut the threads into it. There lies the issue. The rod is 14mm OD with 10 TPI acme style Left hand threads. It does not look quite like acme or square cut threads. I was going to try to grind a small internal threading tool but I’m beginning to think matching the profile may be easier if I cut external threads and make tap.

The material is brass and the hole is .850 deep. The threads are approximately.080 tall per side.

The ID of the hole is approximately.420

Any recommendations on how you would go at it?

 

I would first determine if the thread is SAE or metric ( probably metric ),

 Acme or trapezoidal (  they look somewhat alike )

[maccrazy2]

The thread is Sae, the od of the threads is 14mm

I believe it was intended to be acme thread but they are not totally uniform.

I found a few posts where people had run into the same issue and had the threads measured at a place that had the proper gauges or ? And they ended up with the same thing. It’s a metric diameter rod that has 10tpi cut into it.

I’m going to mess with it this weekend and see how good of a fit I can come up with.

[maccrazy2]

Well it took me three hours but came out pretty well for a first attempt at making a tap. Grinding the tool to cut the threads proved to be a little more difficult than I think it should of been as the threads on the screw are worn throughout its travel. I just need to heat treat it and give it a test cut.

[bruski]

Great job on your tap, it looks like a factory made one.

 

 

bruski