Restoring old lathes, backlash in leadscrews

[John S]

Why do you need a die ? Just buy a spare screw from Myford or Jim Marshall who breaks Myfords.

http://www.homeworkshop.org.uk/

[irving2008]

Why do you need a die ? Just buy a spare screw from Myford or Jim Marshall who breaks Myfords.

http://www.homeworkshop.org.uk

I could, but thats £30 or more, plus if I am going that route I'd rather replace with something metric as its more useful. A 150mm length of TR10x2D and a bronze nut would be cheaper...

[John S]

You will never cut an accurate thread for a leadscrew with a die be it imperial or metric.

[irving2008]

You will never cut an accurate thread for a leadscrew with a die be it imperial or metric.

Good point... but then you need a lathe and thread-cutting ability to make one. Do you know of a source of 3/8 x 10tpi ACME threaded rod other than buying a Myford leadscrew?

[BillTodd]

You will never cut an accurate thread for a leadscrew with a die be it imperial or metric.

Quite correct. You'd be better off just bodging something with a bit of threaded rod!

Irving;
I've just been looking at Tony's lathe site: If the lathe has any historical value I suggest you do not cut the nut as I suggested, it would devalue the lathe considerable.

I'd offer to make you a LH square threaded nut (sounds like a challenge :)) , but my Hardinge will not cut 8 tpi (a major PIA).

I think the best thing to do would be to replace the whole handle, screw and nut. Perhaps using the TR10x2 trapezoid with a metric dial, although I agree with John, adapting a part from another lathe could save a lot of work.

[irving2008]

Quite correct. You'd be better off just bodging something with a bit of threaded rod!

Irving;
I've just been looking at Tony's lathe site: If the lathe has any historical value I suggest you do not cut the nut as I suggested, it would devalue the lathe considerable.

I'd offer to make you a LH square threaded nut (sounds like a challenge :)) , but my Hardinge will not cut 8 tpi (a major PIA).

I think the best thing to do would be to replace the whole handle, screw and nut. Perhaps using the TR10x2 trapezoid with a metric dial, although I agree with John, adapting a part from another lathe could save a lot of work.

I think you are right, tho what historical value the lathe has is moot.

I can get a 18" of 3/8 x 10 LH ACME (enough for both top and cross-slides) for $20 inc shipping and a LH tap from RDG for £10. A brass block off eBay (enough for 5 nuts) is £6, and some steel stock to make the shaft I have already.

Plan would be to turn a new shaft (basically 3/8" dia rod with a 7/16" dia x 1/8" wide section which locates in the base of the brass support. The end of the shaft turned down to 4mm. Centre drill the new screw 4mm dia and loctite/pin the screw to the shaft.

Mill a block of brass to size with a lug on top, turn the lug round on the lathe. Drill out the block and tap (remembering to turn it backwards!)

How hard can that be? :whistling::nope:

Later I may remake the brass support to incorporate a dial (but then I'd have to make a 4th axis indexer to engrave it on the mill... hmmm small chuck, a bearing and a 50tooth gear would give me something I could engrave 50marks, equal to 2 thou steps...)