Leadscrew suppliers

[Len Morris 2Participant @lenmorris2]

A while ago I bought an Ex MOD Adcock & Shipley plain hand horizontal milling machine. Its a nice size for the small workshop with a 24×7 table. It was very cheap as nobody wanted the plain hand operation where the table was simply moved by a lever. I altered it for a 10 tpi lead screw with ball handles and 100 division dials.

Looking for a lead screw I found them far too expensive expensive. In the end I just used a length 3/4 Whit threaded bar. Cheap as chips and very easy to make the nut. I think we get too hung up about square threads. I hasn't worn after many years and will cost practically nothing if it ever does need replacing.

Works a treat and worth considering for a machine that only sees amateur use.

Edited By Len Morris 2 on 13/07/2020 09:41:43

[old martParticipant @oldmart]

That 3/4" W which is 10tpi sounds like a good idea, and if you are not sure of the accuracy, then it would not be hard to do some tests with different measured movements against the dial readings. The OP could use a suitable metric equivalent, although getting hold of trapezoidal stock is much easier in the UK.

[Len Morris 2Participant @lenmorris2]

Agree about the accuracy of commercial thread bar. It's not going to match true lead screw standards. However, the dials get me within 5 thou and if I need better (depending on the job) it's easy enough to put a DTI on it for the final cut.

I also use my miller for turning large diameters jobs up to 20 inches. Over arm removed, 8 inch 4 jaw mounted on spindle nose, tool post mounted on table and knee height used to give center height. Disks, drums and alloy wheels no problem. With a DTI I can get within 1/10 of a thou if needed. Obviously no tail stock but suppose you can't have everything!

[Ian PParticipant @ianp]

My take would be that on a manual mill (ideally with DRO) if you use bog standard threaded rod the pitch accuracy can be 'improved' by having a much longer nut that engages over a high number of threads. I was told (yonks ago) that this averages out pitch changes and helps reduce backlash.

Ian P

[Len Morris 2Participant @lenmorris2]

Good comment Ian. My nut is some 40 mm long. There wasn't room to put anything longer under the table. Once made it was bored out 10 though, split on one side and adjusted onto the threaded rod by 3 cap screws to get rid of backlash. Works fine but again, it is commercial threaded bar and I wouldn't pretend it's as accurate as a proper ground lead screw. Wish I could afford a DRO !

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Len Morris 2 on 13/07/2020 21:21:25:

Good comment Ian. […]

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Agreed

The only caveat being that both the long nut and the screw will wear comparatively rapidly, if they are busy averaging-out all those variations.

… Still a good bargain-price solution though !

MichaelG.

[Ian PParticipant @ianp]

Posted by Len Morris 2 on 13/07/2020 21:21:25:

Good comment Ian. My nut is some 40 mm long. There wasn't room to put anything longer under the table. Once made it was bored out 10 though, split on one side and adjusted onto the threaded rod by 3 cap screws to get rid of backlash. Works fine but again, it is commercial threaded bar and I wouldn't pretend it's as accurate as a proper ground lead screw. Wish I could afford a DRO !

I would say that igaging or igaging type of DRO's are pretty affordable and the accuracy is adequate (same technology as digital calipers) so ideal for budget home engineering where you are making parts to fit each other rather than to volume production interchangeability. Backlash and feedscrew errors become almost unimportant

Ian P

[Ian PParticipant @ianp]

Posted by Michael Gilligan on 13/07/2020 21:37:31:

Posted by Len Morris 2 on 13/07/2020 21:21:25:

Good comment Ian. […]

.

Agreed

The only caveat being that both the long nut and the screw will wear comparatively rapidly, if they are busy averaging-out all those variations.

… Still a good bargain-price solution though !

MichaelG.

I've just been trying to think about the wear aspect..

Small nut, wears more than the leadscrew. Make the nut longer and its lasts longer (more metal to wear away) but presumably wears the leadscrew by taking the highs of the threads that are out of pitch relative to the average pitch. Once the screw high spots are worn away, the lead of the screw becomes a more consistent pitch.

No idea if this is what really happens but I have a vague memory of Joseph Whitworth using long nuts on early metrology equipment.

Ian P

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Ian P on 13/07/2020 22:33:24:

Posted by Michael Gilligan on 13/07/2020 21:37:31
[…]

The only caveat being that both the long nut and the screw will wear comparatively rapidly, if they are busy averaging-out all those variations
[…]

I've just been trying to think about the wear aspect..

[…]

.

Good thinking, Ian

… In reality the distribution and severity of the wear will [I believe] be largely determined by the nature of the errors in the ersatz leadscrew. : Pitch variations, lumps & bumps, eccentricity, etc.

MichaelG.

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P.S. ___ Yes : Sir Joseph Whitworth used long nuts on his metrology equipment, but he also used very good leadscrews.

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Edited By Michael Gilligan on 14/07/2020 10:31:55

[Len Morris 2Participant @lenmorris2]

Can't understand all the concern about wear. Lubrication and an adjustable nut takes care of all that and incidentally never had to adjust the nut since it was installed. I probably use my miller at best for say an hour week. It's for a home workshop, not industrial use!

I find backlash on a miller to be very important, DRO or otherwise. On some jobs it can be very difficult to avoid a clime operation without a complete reset. Backlash under those conditions is not pleasant at all.

[duncan webster 1Participant @duncanwebster1]

For light climb milling I manually push the table in the direction of travel with power feed on so that the leadscrew is just controlling the speed, not actually driving. I don't do this with big cuts!

[Ian PParticipant @ianp]

My comments about wear were triggered by Michael G's mention that a long nut setup would have 'comparatively rapid' wear.

What I said earlier about backlash was mainly referring to positional error, slide friction or sticktion has always been (on my machines) enough to overcome the climb cutting forces. Maybe I have my gibs set to tight?

Ian P

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Len Morris 2 on 14/07/2020 11:27:23:

Can't understand all the concern about wear. […]

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___ What concern ?

I, for one, was just engaged in conversation

MichaelG.

[Len Morris 2Participant @lenmorris2]

Michael,

Fully accepted. No intention to be contentious.

Len

[Michael GilliganParticipant @michaelgilligan61133]

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