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

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

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

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

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

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

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,

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

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

Yes.

G.