Metric ML10 lead screw threadform

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Neil Wyatt on 25/04/2018 15:27:26:

Cripes, it was one of Martin Cleeve's articles in model engineer… probably in the 50s or 60s… does that help?

.

Thanks for that, Neil

I really just wanted to know whether it was a direct quote from Martin Cleeve, or your interpretation of what he meant.

… Not a problem, I may find it sometime.

MichaelG.

[RobinParticipant @robin]

I bought mine 12/6/89, still going strong and I still have the paperwork .

The price list reveals all…

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Robin on 25/04/2018 20:38:01:

The price list reveals all…

.

.

Regrettably not all, Robin

It confirms the 3mm leadscrew pitch, but does not reveal its thread-form

… which is, I believe, where we came in.

MichaelG.

[Neil WyattModerator @neilwyatt]

Posted by Robin on 25/04/2018 20:38:01:

I bought mine 12/6/89, still going strong and I still have the paperwork .

The price list reveals all…

Given the paranoia about personal details – you do know that photo includes an address for you…?

Surprised your Myford wasn't priced in guineas

[Paul Smith 37Participant @paulsmith37]

Excuse the thread hijack, but can somebody with a ml10 Metric with a metric lead screw tell me how much slop you have in the lead screw mechanism please? ive got around .6mm as indicated on the leadscrew handle, roughly a third of a turn of slop before it does anything. Thanks In advance Pauly

Edited By Paul Smith 37 on 01/03/2020 09:33:10

[Paul Smith 37Participant @paulsmith37]

Thanks Again!

[HopperParticipant @hopper]

Posted by Paul Smith 37 on 01/03/2020 09:32:39:

Excuse the thread hijack, but can somebody with a ml10 Metric with a metric lead screw tell me how much slop you have in the lead screw mechanism please? ive got around .6mm as indicated on the leadscrew handle, roughly a third of a turn of slop before it does anything. Thanks In advance Pauly

Edited By Paul Smith 37 on 01/03/2020 09:33:10

That is some slop but not enough to be too worried about.

You should check that some/a lot of it is not from leadscrew endwise movement. This is adjusted on most lathes (i'm not familiar with the ML10, being an ML7 guy) by tightening up the adjusting nut in the middle of the leadscrew handwheel, and observing the gap between the shoulder or collar on the leadscrew and the right-hand leadscrew mounting bracket (next to the handwheel).

If it is not that, the slop is not much to worry about. It does not affect the performance of the lathe. Slack is taken up and stays taken up once the tool starts cutting. Just be sure to lock the carriage when facing etc.

My old M-Type, with similar 8tpi circa 3mm pitch leadscrew, had the threads in the half nuts worn down to .015" (.38mm) thick, giving about 2.6mm of slop, but still worked perfectly. In fact, I used it to machine its own new replacement halfnuts, which have worked perfectly ever since.

Check the ML10 owners manual too. It may have some adjustment of the halfnuts like the ML7 to tighten them up a bit. Others with ML10 specific knowledge will surely be able to comment on that shortly.

Edited By Hopper on 01/03/2020 10:01:16

[Mick B1Participant @mickb1]

Posted by Hopper on 01/03/2020 09:58:56:

Check the ML10 owners manual too. It may have some adjustment of the halfnuts like the ML7 to tighten them up a bit. Others with ML10 specific knowledge will surely be able to comment on that shortly.

Edited By Hopper on 01/03/2020 10:01:16

IIRC there's a grubscrew to set the standoff?

Paul Smith 37 – have you looked at the halfnut threads? If there's impacted crud in there, it can limit the closure of the halfnuts so that the narrower crest of the leadscrew has extra clearance in it before it meets the flanks of the halfnut thread.

[Paul Smith 37Participant @paulsmith37]

No I havnt stripped it yet as I’m still using it, I’ve also acquired another cross slide to fit as a chap called Mike from here is going to refurbish the old one..So I’ll strip the lot and check it out. Also the tailstock is very stiff, yet another job.!

[Howard LewisParticipant @howardlewis46836]

Kempe's Engineers Year Book for 1982, Section E2/12 refers to ACME threads and BS 1104. describing ACME threads as being symmetrical with an angle of 29 degrees between the flanks.

The proportions are given as : h = 0.5P and s = 0.3707P

In this context, P = the pitch, s = the width of the crest of the thread, and h = Thread depth root to crest..

So, using those proportions, there would seem to be no reason why an Acme FORM thread could not be made with a metric pitch and proportions, rather than having to be in Imperial units.

In which case an ACME thread with a 3 mm pitch would have a depth of 1.5 mm and a crest or root width of 1.1121 mm.

Howard

[HopperParticipant @hopper]

Zombie thread alert on the threadform issue.

[Clive HartlandParticipant @clivehartland94829]

On the ML10 the bottom half nut has a grub screw which you can adjust to give minimum clearance between the two half nuts after you have cleaaned out the crud in them. This is a very small skt head grubscrew so you need to get them out to get an alan key to fit. Of course after you have done all this you lose that allen because you forget where you put it!

I am at the moment in the priocess of making a device which sits over the leadscrew to stop all the swarf from falling on the lead screw. Only one part will attach to the carriage and it has a split tube which can easily be detached etc.

Sadly at the moment I am unable to work on it due to a damaged spinal disc. This makes standing around painful. Had three nerve bloc injections a short while back which did nothing! Standing is painful, sitting is painful and disturbed sleep normal now.

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Howard Lewis on 01/03/2020 15:58:19:

[…]

So, using those proportions, there would seem to be no reason why an Acme FORM thread could not be made with a metric pitch and proportions, rather than having to be in Imperial units.

In which case an ACME thread with a 3 mm pitch would have a depth of 1.5 mm and a crest or root width of 1.1121 mm.

.

Duly noting Hopper’s observation …

• Here, for reference, is pictured a pair of half-nuts “most probably unused” **LINK** https://www.ebay.co.uk/itm/GENUINE-MYFORD-ML10-LATHE-METRIC-LEADSCREW-HALF-NUTS/233042304691
• They are clearly not a square thread-form [so one would hope that the screw is also not]
• The detailed thread-form is not reliably measurable from the photo, so
• Whether 30° Trapezoidal or 29° B’stard ACME remains debatable
• But [going by the nuts] … I doubt that Myford felt obliged to tolerance the screw to a tenth of a micron

MichaelG.

[Howard LewisParticipant @howardlewis46836]

If Myfords were producing ACME form threads for Imperial lathes, I doubt if they would go to the capital and labour costs of changing over the tooling to Trapezoidal, when a Leadscrew could be produced with the Metric pitch, merely by changing the ratio between the manufacturing machine .Leadscrew and its Chuck.

If ACME works on when made to Imperial dimensions, it would work if made to Metric. The task of the Leadscrew is to move the Saddle along the bed of the machine, so the pitch is the important dimension, and is only likely to cause difficulty if the Leadscrew and Nut are markedly different from each other.

But I am sure that these would be the thoughts of a Production Engineer at Myfords, (and probably in a lot of other factories ).thinking in terms of Fitness for Purpose.

Otherwise, it would be total blasphemy to fit Metric ballscrews to a machine that left the factory with old fashioned Imperial plain Leadcsrews and Nuts!

Howard

[Paul Smith 37Participant @paulsmith37]

Well ive got it to bits and found the metric leadscrew is worn in the middle. so i need a new one!

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Paul Smith 37 on 14/03/2020 20:31:55:

Well ive got it to bits and found the metric leadscrew is worn in the middle. so i need a new one!

.

In view of Howard’s comment … It would be very helpful to posterity if you could check an unworn section of your leadscrew and tell us all what profile it really is.

MichaelG.

[Paul Smith 37Participant @paulsmith37]

Ill put up a picture tonight, im out for lunch right now, maybe somebody could identify it?

[Paul Smith 37Participant @paulsmith37]

The top section is the worn bit

 

 

And the bit above is the good bit.

Edited By Paul Smith 37 on 15/03/2020 18:26:50

another angle shot

Edited By Paul Smith 37 on 15/03/2020 18:29:21

[Author]

Posts