Advise on Myford leadscrew

[Basil]

I will be doing some thread turning soon, Is this leadscrew for the scrap bin. As a thought could this 4 1/2 inch bad section be moved by shifting the leadscrew towards the gears and extending the other end with drill rod? I cant see I will be ever threading down that far to the tail end. The clamping nut half's are shot so will definitely be replacing them. Thanks

 

[fcheslop]

On My previous ML7 I turned it end to end . I did have access to another lathe so altering the ends of the screw was possible. I dont think the screw will go through the head spindle

 

[goldstar31]

RDG Tools should have the smaller diameter leadscrew of 8TPI but I recall 'martin Cleeve( mentioned at some length today) actuall took the less worn tailstock end and it al was joined up again. It was described in model Engineer. But______________________-

How have you determined that it is 'shot'? It may well be that the clasp nuts can be re furbished enough to give the old machine a new lease of life. I've forgotten what the clasp nut material is. If it is iron or steel it can possibly be retinned with metal from car/van/lorry main bearing shell metal. I've done this on a well worn feed screw of a Pools Major- which no one now has the foggiest knowledge. Otherwise the advent of Turcite and Moglice have changed the art of reconditioning othr wise worn out bearings, spindles and feed screws. I recall once that I had the top of a ML7 bed 'Blancharded' for say £25 or £50 I built up the worn first 6 inches of Number One front shear and scraped the Loctite in this caseand apparently a filled ceramic powder, all was well. I finished the job( I'm digressing a bit)but came off the un-used Number 4 shear.
Respectfully, you have to move into a new technology. I had an absolutely clapped out Super 7B - undrthe saddle on the narrow guide principle 'Turcited almost as new. Mine was done by Blue Diamind at Shildon, County Durham on an Italian slide ways grinder and the cost for what was beautiful slideways grinding of the vbed and building up and maching the saddle was £250.

Do have a re-think and intrigue us on your progress.

Norman

 

[fcheslop]

The nut is the same monkey metal as the other feed screws and will be worn

 

[goldstar31]

The nut is the same monkey metal as the other feed screws and will be worn

So the two clamps could be 'blued' and fairly esily scaped to take the slop out?

Meantome of a personal note- how are you coping?

Regards

Norman

 

[fcheslop]

Hi Norm, becoming stir crazy . Just keeping out of the way until Vlad the Impaler calls
The half nuts could be made to fit with a bit of ingenuity . I turned the screw around and made a new tail end and just made a different coupling at the head end. It was not a big job and on my old banger of a machine made a big difference when screw cutting . The rest of the machine was badly worn and my ancestry prevents me from spending that illusive stuff to often.
Although I did buy a factory refurb when they closed down. The place looked like a retirement home for fitters
Keep well all
Frazer

 

[goldstar31]

The nut is the same monkey metal as the other feed screws and will be worn

I've just got a Christmas Box9 sorry, bottle of Monkey's Shoulder Malt whisky.

 

[Basil]

Not sure what they are made of. Seems heavier than aluminum but not steel? Is it really pot metal?

 

[goldstar31]

It will be a zinc alloy but having a metallurgy discussion isn't going to cure what is showing up as a sloppy situation that you will be wise to attempt to eradicate. you need to fashion scraper to get into the bits that show up when the nuts are 'blued' then scraped, then blued and scraped until they fit the best part of the lead screw which probably is at the extreme end of your screw. I can't recall it in 'Connolly' but that is my opinion without my examination.

Best wishes

Norman

If you have a bit of car body bodge, it might be possible to add a smear of resin into the suspect threads and see what is wrong It's a bit like taking a dental impression. Yea, yea my daughter is a consultant orthodontist like her late Mum -- and has Covid-19 along with her senior consultant husband who is down with it- and I'm feeling that bit 'testy' but it is worth a try. Use a candle to soot up the lead screw to act as a release agent. Sounds a bit barmy but I did something like that to a feed screw.
Let me know your findings

 

[skyline1]

The leadscrew on my old Myford was in similar condition It was ACME type thread at the ends as it should be but more or less Whitworth at the worn bit I ended up having to scrap it but luckily a friend had a spare one he was willing to sell at a reasonable price.

Older Myfords have a slightly smaller leadscrew (5/8") than more modern ones BTW.

I think you might still be able to get one from RDG tools but it is going to be expensive (VERY expensive like everything else Myford they sell, asset stripping racketeers !)

Dressing the claspnuts down so they grip tighter does not work I tried it you end up with a very small range of movement where they are tight enough to be accurate but do not bind.

I think the Myford principle was that the claspnuts being made of Zinc Alloy wear before the leadscrew does and can be easily and cheaply replaced.
However it doesn't seem to work in practice as the nuts seem to go on for ever and the leadscrew wears.

The claspnuts can also be had from RDG but once again they are not cheap.

Best Regards Mark

 

[steveastrouk]

We never had problem with our leadscrews on our production used Myfords- but we would replace the halfnuts every couple of years. Its a long time since I used a Myford, how expensive are the nuts these days ?

 

[goldstar31]

Mark, You may be right but I have double Acme threads on my slightly exotic small but I have a perfectly norma versatile 'normal 20TPI. Whitworth vertical screw thread on my Stent T&C. In fact it is no more than standard studding.
Again, I have a 3mm leas screw on my Sieg- that looks like Whitworth form- but isn't. After all we are simply discussing screwcutting and I have truncated Whitworth screw bed bar on my Quorn nand Cleeve in nhis wisdom made screws professionally as well as writing his excellent book but wrote to his customoers whether they minded having the Whitworth screws without rounded crests- and the did not reply but continued to order from him.
I therefore conclude that once the poster gets his clasp nuts to fit the worn leadscrew albeit with the necessary gap of oil it doesn' t matter a hoot.



Have a nice day

We never had problem with our leadscrews on our production used Myfords- but we would replace the halfnuts every couple of years. Its a long time since I used a Myford, how expensive are the nuts these days ?

Have been in the Pricing Game recently and bought a ;as New Super7B with Power cross feed, I had checked the price of a non- gear box machine that had been reconditioned by the successors to the now Defunct original company. The price of one with no motor or any v=centres chucks or whatever is a cool £3000 and then transport to be added.
Myford continue to be made with power cross feed and it would seem that to start building a Myford(RDG) having bought the Myford name, people are having the think of £8000. Yes!

Now n old clapped out ML7 CAN be resurrected to be factory fresh about b6 times which begs the question of not going the whole hog and approaching either RDG Tools for a quotation or douing as I did with an old grey 'softer gear box Super7 with a saddle that looked like a cattle grid run over by a tank and being slideays ground and Turcited at a local machinery restorer . I did the rest of the work but the bed etc was 'slid in to the normal proper work and therefore was competitively and acceptably priced.
It depends on what an owner of what must be a basket case but has great potential if the owner is prepared to go . I was an accountant and cannot predict that
I hope that this helps?

Norman

 

[deverett]

A guy called Tony Crowe - a member of the Myford io group - used to sell bronze half nuts. At least I think they were for the main leadscrew, or was it for the cross slide? !

Dave
The Emerald Isle

 

[skyline1]

Norm

Nothing wrong with Whitworth feedscrews or other thread forms for that matter.
The feedscrews on the Z axis of one of my 3d printers are nothing more than lengths of M8 studding and they work fine (and hold very close tolerances).

The point I was trying to make was that the leadscrew was so badly worn that it's thread on the unworn ends was it's normal trapezoidal (ACME) form but on the worn centre section the flanks were worn to such an extent that the thread form was approaching that of a Whitworth on the same leadscrew.

I tried dressing down the half nuts to get a snug accurate fit on the worn section but found that I could only get a few inches of travel before they started binding on the less worn parts.

Dave

I remember seeing these too and IIRC they were actually cheaper than the zinc alloy Myford ones. Hmm something amiss there

Best Regards Mark

 

[goldstar31]

Mark
No one but the poster has an inkling of actually what is wrong with his lathe. Nothing is wrong with my lathes that I cannot fix .

 

[skyline1]

Quite so Norm

There is an Air Force saying you probably know off by heart.

"Nothing is beyond repair but some things are beyond economic repair"

Best Regards Mark

 

[goldstar31]

two expressions
Nil Illigitimi Carborundum
and

Per Ardua Asbestos

And the other ones are quite unprintable

Take Care

Norman

 

[redhunter350]

Basil, have a look at this thread on another forum for supplies of Acme threaded bar UK Supplier of Imperial Acme Threaded Bar? | Model Engineer
As for the half nuts they are as far as I am aware made from Mazak , your do look well worn so I would bite the bullet and purchase replacements, if you look after them they will last a great many years.
John

 

[ALEX1952]

IF it is Mazak which I find suprising given the wear it will take, It would be possible to use the unworn end of the lead screw as a pattern and cast a replacement. Mazak has a very low melting temp and lends itself to complex castings and is cheap hence its common usage.

 

[abby]

I used white bearing metal to cast new "teeth" onto my worn half nuts .
the set up is pretty straight forward and doesn't really need a description other than to say that most of the original threads are removed , leaving just the outers for location , and holes are drilled through the castings for pouring access. The bearing metal can be purchased online and the repair lasts .
Dan.