ml4 half nut

[wayneParticipant @wayne]

[wayneParticipant @wayne]

Hello everyone

ive not been here for a while due to my illness getting the better of me for a time and with MS you never know when it will strike and what damage it will leave you with or how long it will take for you to recover .but I back ta daaaa and now I can have another attempt at completing my myford ml4. in a earlier post I did I asked for info on how to sort it out and set it up ,I got a lot of sound advice and help sourcing a few parts to get things going .quick update on my lathe ,I stripped it cleaned it then painted it .started setting things up ,and that's when the MS reared its ugly head and made me come to a brick wall and stop so a break from thinking to hard and recharge ready for round 2 ding ding . anyway im trying to get a good half nut as mine is very worn and is replaced the complete apron I got from I nice chap on here .but the half nut on it works but not very well but better than my original apron ive tried making a good set from the 2 but there all worn to some degree my leadscrew is ok and taking there time to engage so if this all this is understandable please advise if anyone can repair them ? ie a bronze sleeve maybe ?

kind regards wayne

[David George 1Participant @davidgeorge1]

Hi Wayne. I have M type Myford and it has a similar setup with a half nut and a plain fixed half to guide and push against. The one that I have has been replaced with a half nut that has been silver soldered in place. After machining away the original nut and replacing with a made up replacement part. I didn't do the repair as it is how I received it. It looks fairly easy to do, just screw cut a new nut sleeve, slice in two, machine the old nut and solder new one in its place.

David

[Neil WyattModerator @neilwyatt]

Hello Wayne, welcome back into the ring, good to have you back.

Use the down time for planning and do what you can when you can, it's not a competition!

Neil

[wayneParticipant @wayne]

Thanks again Neil im pleased to be back and thanks David for your input . but that's the problem my half nut is hit and miss so screw cutting is not possible even if I left it engaged and cut back and forth very slow the nut jumps out of mesh then re engages ive tried the saddle gib incase it was to tight and apron gib . I have watched vids of how you described .and yes it does look pretty straight forward .but my nuts don't work and this is why im against the wall on this one .thanks again.

regards Wayne

[Ady1Participant @ady1]

I had a couple of bronze half nuts I burned through in a couple of years. I replaced them with an aluminium nut I cut myself before things went south for the bronze ones, still fine 4 years later

Very soft to cut, I did it by hand with a handle in the headstock

Edited By Ady1 on 21/09/2017 02:33:02

[HopperParticipant @hopper]

Posted by Ady1 on 21/09/2017 02:31:36:

I had a couple of bronze half nuts I burned through in a couple of years. I replaced them with an aluminium nut I cut myself before things went south for the bronze ones, still fine 4 years later

Very soft to cut, I did it by hand with a handle in the headstock

Edited By Ady1 on 21/09/2017 02:33:02

How did you go soldering the aluminium half nut sleeve to the original bronze casting? Or did you Loctite it?

[David George 1Participant @davidgeorge1]

Can you use a tap to make a new nut or is there somone near you who could cut it for you . Where in the country are you.

David

[Ady1Participant @ady1]

How did you go soldering the aluminium half nut sleeve to the original bronze casting? Or did you Loctite it?

I skimmed the old half nut casting down as far as possible, then shaped the new halfnut so it was slightly proud of the bronze edges, (it almost "clicked" onto the casting), then used a very short grubscrew through the original casting

I would use a wholenut if I did it again, and dispense with the threadless top part of the arrangement, much simpler IMO

edit no, I would keep the top section and shape the wholenut to fit into the top and bottom part, much stronger under load (shape the wholenut so it looks like a pipe with flanges)

I wouldn't miss the rack, 95% of the time you're at the headstock + 6 inches

Edited By Ady1 on 21/09/2017 09:41:11

[Brian WoodParticipant @brianwood45127]

From memory, I think the ML4 lathe was equipped with a square cut 8 tpi leadscrew. If trying to match that up with ACME form 8 tpi half nuts there is bound to be a mismatch and little hope of getting proper engagement. From what Wayne is saying, that seems to be the present problem.

Moulded Delrin half nuts onto his own leadscrew might be the easiest way to go in the end

Brian

[GeorgineerParticipant @georgineer]

Wayne,

I have an unused bronze leadscrew nut for an ML4, and no use for it. I can't describe it as half-nuts, because it has never been split, and I can't describe it as new because it has been in the cupboard since 1970. It includes various pegs and screws. I can also let you have the original receipt from Myford's.

Send me a PM if you are interested.

George

[wayneParticipant @wayne]

Posted by David George 1 on 21/09/2017 07:50:39:

Can you use a tap to make a new nut or is there somone near you who could cut it for you . Where in the country are you.

David

hi david

im in tamworth staffs and most of the small workshops around here have closed up now ,and I don't know anyone with a lathe that could do the job for me ,and I don't drive anymore and cant get about some days due to my illness .my wife calls me a shed hermit ,ive looked for a tap but I cant find one and im not 100% sure what the lead screw thread is ? I know it 8 tpi left hand . but is it a true acme ? or a square thread of some kind I cant find a true spec ? or have I missed something ?

regards wayne

[wayneParticipant @wayne]

Thanks everyone

for a warm welcome back here ,and to everyone who got involved in this post and your input to help solve things .

I wont to let everyone know im now sorted thanks to Georgineer who I now call Super George ,a great fella who came to the rescue once again . and once im 100% up and running I will get all my pics and put up an album of the the ml4

kind regards Wayne

[Jon CameronParticipant @joncameron26580]

Hi Wayne,

I'm too trying to sort a poorly ML4, the half nuts on mine are threaded top and bottom, I've recently discovered that the Lead screw is shimmed out at the change gear side, and I now know why. The nuts have been machined about 1mm off the center of the Lead screw. So it pulls it over, the previous owner has obviously shimmed the wrong part, and should have shimmed under the nuts instead. Anyway to my point. On my ML4 the half nuts can over engage, meaning they open back up again, not much but enoufh to cause issues.

If the handle is fully up the half nuts are open, when at around 7:30 (the hour hand on a clockface is easier to describe than measuring the proper angle) the nuts are fully engaged, if its at 6:00 then the half nuts have begun to open up again.

If it doesn't turn out to be the thread been incorrect as said above it may well be something as simple as I've found with mine.

Edited By Jon Cameron on 22/09/2017 11:41:02

[wayneParticipant @wayne]

Posted by Jon Cameron on 22/09/2017 11:40:15:

Hi Wayne,

I'm too trying to sort a poorly ML4, the half nuts on mine are threaded top and bottom, I've recently discovered that the Lead screw is shimmed out at the change gear side, and I now know why. The nuts have been machined about 1mm off the center of the Lead screw. So it pulls it over, the previous owner has obviously shimmed the wrong part, and should have shimmed under the nuts instead. Anyway to my point. On my ML4 the half nuts can over engage, meaning they open back up again, not much but enoufh to cause issues.

If the handle is fully up the half nuts are open, when at around 7:30 (the hour hand on a clockface is easier to describe than measuring the proper angle) the nuts are fully engaged, if its at 6:00 then the half nuts have begun to open up again.

If it doesn't turn out to be the thread been incorrect as said above it may well be something as simple as I've found with mine.

Edited By Jon Cameron on 22/09/2017 11:41:02

Hi Jon and thank you

what you say makes complete logic I didn't even think of that , yes mine also over engages and it makes them start to open back up . but when ive sorted the nut I will drill through and tap the lever base (round bit ) and indent the base and use a small spring and ball bearing held with a grub screw .in unlocked and locked positions which in affect should give a positive hold up and down and rest at each point ?

[Brian WoodParticipant @brianwood45127]

Jon,

It is a long time ago now that I sold my Dad's old ML 4 but I seem to remember that the operating handle for the lead screw half nuts can be rotated with respect to the screwed stud upon which it is mounted. There should be a lock nut to secure a chosen position which may put your situation right or more tolerable.

On your lathe, which we have established in private correspondence, is actually an ML1 or 2, the lead screw will be square cut 8 tpi, I think left hand, but the point I am making is that engagement of the half nut threads is not as forgiving as it is with ACME form lead screws.

The square cut lead screw will also be present on Wayne's lathe unless some previous owner has upgraded to an ACME version—rather unlikely but still a possibility. It seems that Georgineer has put matters right for him anyway

Regards Brian

[Neil WyattModerator @neilwyatt]

Martin Cleeve recommended a modification to the ML7/S7 that would also apply to the ML4, a threaded hold in one half nut for a long grub screw that limits how tightly the nuts can close. Leaving a consistent small gap makes them less sensitive to bits of swarf and aids repeatability.

Fitted as standard to Chinese Mini Lathes and other quality machines

Neil

[Jon CameronParticipant @joncameron26580]

Wayne that's not a bad idea, it'll hold it to location but allow easy movement. Just thinking on that idea a moment, could the handle be held securely in an offset position for the tailstock to drill and tap the hole. Yes a pillar drill would be much more convenient but I've only the lathe and a 4" vise, yes my tool collection is huge. I've a hand drill but I think I'd drill off square doing it free hand.

Brian I'm still not convinced it's an ml1 or 2, yes the nose thread is the same for the spindle, but the bed for the 1 and 2 was much shorter than the lathe ive got. Maybe a spindle was used in my lathe from an ml2? Plus I thought the 1 had a fully cast in headstock, meaning the headstock and bed were all one casting???

 

Edit: just been to the shed to look at the lathe, there's no adjustment on the handle to allow for posision as the back of the handle is machined with grooves that engage the bars on the back of the half nuts. I have managed to reduce a lot of the deflection of the Lead screw. It was 80thou, now it's only 40 thou, by removing the shims by the  headstock that were under the Lead screw bracket. Obviously put there to correct the deflection, and instead undid the two bolts that hold the apron on, and moved the apron in a little. As I say this means there's now only 40thou of deflection, I think I could improve on that further by shiming the back of the half nuts by 40thou, but I don't know if it'll mean they'll engage before I want them to. Trial and error here I think.

I also want to do another mod which is to bring the rack out by 2.5mm which will mean more of the gear will contact it. Hopefully meaning I'm running on a fresh surface. Washers may be an easy quick fix for now. 

Jon

Edited By Jon Cameron on 22/09/2017 15:58:08

[Jon CameronParticipant @joncameron26580]

Posted by Neil Wyatt on 22/09/2017 14:27:00:

Martin Cleeve recommended a modification to the ML7/S7 that would also apply to the ML4, a threaded hold in one half nut for a long grub screw that limits how tightly the nuts can close. Leaving a consistent small gap makes them less sensitive to bits of swarf and aids repeatability.

Fitted as standard to Chinese Mini Lathes and other quality machines

Neil

That mod is logged in the memory bank for later too

[Brian WoodParticipant @brianwood45127]

Jon,

I might be very wrong but were long bed models of these lathes made perhaps, Ideally someone with pictures of a genuine ML 1/2 will resolve the cast headstock integral with the bed; I think the ML3/4 spindles were longer too for a substitution who knows?

Regards Brian

[wayneParticipant @wayne]

Posted by Jon Cameron on 22/09/2017 15:28:10: yes there are grooves in the back of the lever .so take lever off drill from the back in the area you choose which I think will be on the outside of the groove then bolt it back up on the apron lock the nut engaged buy tightening the center bolt and mark through the hole location .after doing that make a small hollow in the apron casting to take a small bearing and spring .? you could drill it via your lathe offset in a 4 jaw

Wayne that's not a bad idea, it'll hold it to location but allow easy movement. Just thinking on that idea a moment, could the handle be held securely in an offset position for the tailstock to drill and tap the hole. Yes a pillar drill would be much more convenient but I've only the lathe and a 4" vise, yes my tool collection is huge. I've a hand drill but I think I'd drill off square doing it free hand.

Brian I'm still not convinced it's an ml1 or 2, yes the nose thread is the same for the spindle, but the bed for the 1 and 2 was much shorter than the lathe ive got. Maybe a spindle was used in my lathe from an ml2? Plus I thought the 1 had a fully cast in headstock, meaning the headstock and bed were all one casting???

Edit: just been to the shed to look at the lathe, there's no adjustment on the handle to allow for posision as the back of the handle is machined with grooves that engage the bars on the back of the half nuts. I have managed to reduce a lot of the deflection of the Lead screw. It was 80thou, now it's only 40 thou, by removing the shims by the headstock that were under the Lead screw bracket. Obviously put there to correct the deflection, and instead undid the two bolts that hold the apron on, and moved the apron in a little. As I say this means there's now only 40thou of deflection, I think I could improve on that further by shiming the back of the half nuts by 40thou, but I don't know if it'll mean they'll engage before I want them to. Trial and error here I think.

I also want to do another mod which is to bring the rack out by 2.5mm which will mean more of the gear will contact it. Hopefully meaning I'm running on a fresh surface. Washers may be an easy quick fix for now.

Jon

Edited By Jon Cameron on 22/09/2017 15:58:08

[GeorgineerParticipant @georgineer]

Some simple measurements and observations can identify which of the different models ML1 to ML4 one is faced with.

ML1 & 2: 3 1/8" centre height, 15" between centres, 3 1/2" cross slide travel.

ML3 & 4: 3 1/2" centre height, 24" between centres, 4 1/2" cross slide travel.

ML1 & 3 ('Standard' models): Spindle bearings direct in headstock.

ML2 & 4 ('Superior' models): Bronze spindle bearings, shrouded ball thrust race.

My understanding from lathes.co.uk is that the cast-in headstock was abandoned in 1937, so from then until the ML1 and ML3 went out of production in 1941, all models had the removable headstock.

George

[Jon CameronParticipant @joncameron26580]

Thanks George in sure mine has a 3.5" centre height, will check tomorrow after work. (Just for clarification the centre height is measured from centre of spindle to top of lathe bed?)

Sorry Wayne I seem to be hi jacking your thread, I'll start another of my own

[GeorgineerParticipant @georgineer]

Posted by Jon Cameron on 22/09/2017 22:28:31:

… Just for clarification the centre height is measured from centre of spindle to top of lathe bed?…

Yes.

G.

[wayneParticipant @wayne]

hello there

well today I had to walk away from my lathe before I set about it with a big hammer and angle grinder

after 2 years of messing about trying to get it to work half decent I may be flogging a dead horse ,after changing everything apart from the bed everything as been replaced all gears /tailstock/ saddle /cross slide /compound ect / I even located a better complete headstock as the one that came on the lathe was butchered , so today I was just having a little clean up and fitting some brand new studs to the quadrant and setting up the gears ,when it was running I noticed some oil had run down the headstock face just below the tumble lever and the oil just sat on the join where the headstock meets the bed I noticed the oil appeared to be bubbling ?on that joint the headstock is moving up and down as its running

which tells me its not mating up flat to the bed all bolts are tight .so after all my setting up and getting it to cut straight over a 8" span the headstock will need to be taken off again to take a look and figure out whats next .

wayne

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