Myford ML4 leadscrew dials

Hello,

As i hopefully near the end of the lathe refurb, i am wanting to add graduated dials for the leadscrew. I will be using the lathe for milling with an alomco milling attachment, (the base has an adaptor plate to fit the bed). With the half nuts engaged this should hopefully help to have small increments of movement using the leadscrew handle, instead of larger sometimes jerky movements when using the handwheel on the apron, which is direct drive onto the rack.

Would i be right in saying with an 8TPI leadscrew i will need 125 divisions on the dial, so something like the ML10 dial would possibly be best. I have already become accustomed to using the dials as an approximation to finished size as i know there is the slightest of errors that Myford built into the leadscrews on the carriage and compound.

Thanks in advance

Jon

Yes. Each turn of the handwheel and leadscrew is 1/8" or .125" so you are correct.

My M-type has had the outer diamter of the leascrew handwheel turned flat and the graduations and numbers etched on there. Works very well and very simple. Can be done on the lathe itself by using a plunger engaging with the change gears to index the chuck while holding the handwheel in it. Graduations are put on with a toolbit turned sideways and racking the carriage back and forth. A carriage stop can help get graduations correct length.

I don't know about Myford building errors into cross slide feedscrews etc. Could it possibly be wear after all this time?

Edited By Hopper on 10/06/2020 09:27:30

Hi Hopper,

Yes i had considered that however given the time it would take and that a leadscrew handwheel with 125 graduations is available for £25 i am inclinded to take that route so was just checking. All i would need to do is make an adaptor to get to the 7/16" size as i believe though i need to check that the end of the leadscrew on mine has 1/4" BSF thread.

With regards to the leadscrews Myford used 12TPI leadscrews in the earlier lathes, for the cross slide and compound which creates a small error not a lot but still there.

Jon

Hopper,

Just to to avoid the suggestion that the 'errors' are deliberate, the feedscrews for cross and top slide on these early Myford lathes were made as 12 tpi square form, the dials were given 80 divisions so tool movement was an approximation. Myford say in their handbook that it is probably 'good enough for most purposes'

Regards Brian

Edit I see that Jon got there first with the 12 tpi screws.

Edited By Brian Wood on 10/06/2020 10:16:56

Yeah that might be the smart way to do it.

12tpi thats a bizarre one. Even my 1930s M type has 10.

I can only assume that it was designed so a new one could easily be made with a standard set of change gears if the need arose. Not sure if the standard set of change gears would allow a 10TPI thread? Brian would be better qualified on that one. As ive already said to him elsewhere i'm rubbish at maths hence the original question, i struggle working out gears and ratios. Took me a very long time for the penny to drop with dividing, but that's digressing!

Jon

Nobody works out change gears these days with online calculators available. My favourite is on the Little Machineshop site. 10tpi is doable so not sure about that. Maybe 12tpi was cheaper to buy on or something.

Just to prove the point, 40 T on the mandrel and 50 on the leadscrew with idler(s) as necessary to link them will cut 10 tpi on any lathe with an 8 tpi leadscrew

Brian

I stand corrected. Brian is the last man who can still work change gears out in his head.

I knew that Myfords took over manufacturing the Drummond 'M' type at the start of WW2 because, to quote lathes.co.uk "their contemporary models, the ML1, 2, 3 and 4, were completely unsuitable for professional work"

Could this be because of the inaccuracies in the slide leadscrews?

You might well have a point there Nick. I've never explored why they were unsuitable. Just accepted the powers that be didnt want to use myfords for whatever reason. Perhaps Tony has an answer on this if anyone is just that bit more curious than I.

Jon

I'll let you into the secret Hopper, I use my calculator too!

Regards Brian

Edited By Brian Wood on 10/06/2020 13:49:53

Hi all

I can't remember where I got the idea but I have always understood that the reasons the ML1-4 were rejected for war time work was that they were regarded as too insubstantial for factory production work, and they lacked power cross- feed which made them unsuitable for use on smaller warships and submarines which bounce about too much to allow steady hand feeding. Hence Drummond were told to give Type M production over to Myford and further told to concentrate on producing Maximat ( not exactely sure of type or spelling) production lathes. In those days the Government could just tell everyone what to do and they got on with it!

Rod

Who would want them, and what for?

Although they're maybe at the upper end in terms of quality, early Myfords are typical of any number of the basic pre-war machines sold to amateurs. Small, lightly built, simplistic, and relatively weak. Yes they do good work in skilled hands, but they're not robust and fast enough for production, or suitable for high-precision, or capable in the way valued for prototyping or laboratory work, or good for training servicemen and apprentices. Considerably inferior to Myford's post-war lathes, which killed the range stone dead, and to the contemporary and far more expensive Drummond M.

I don't think anyone with production targets and tolerances to meet would want a pre-war Myford. For similar reasons, despite their many virtues, ML7 and Super 7's weren't popular in industry or education either. They prefer robust precision to delicate precision, and are prepared to pay big money for it.

You don't see industry snapping up Chinese Hobby machines either!

Dave

I seem to recall my old school going over to Colchester Students in favour of the original Myford Sevens. On a later visit the Colchesters had gone, too!

Rod & Dave -

The Drummond/Myford M Type, again according to Lathes.co.uk, "had been adopted some years before as the standard model for the Armed Services."

The powered cross slide was only fitted to admiralty versions of the M type so most of these were not that different to the ML1/2/3/4 in specification, but were preferred for some other reason.

Your points regarding the general capability of the lathe I acknowledge, as has been done elsewhere, but as far as I can tell most of these apply equally to the M Type as well as the ML series..

Edited By Nick Clarke 3 on 10/06/2020 17:16:11

Edited By Nick Clarke 3 on 10/06/2020 17:16:50

With the original 80 division handwheels, each division would be 1.042 thou, which was probably not sufficiently precise. for the accuracy required.

The closest that you can get to for a division on the handwheels to a thou would be to have 83 divisions.

The error would then be x 10^-3 thousands of an inch in each division. The errors would probably then come from the thickness of the lines on the wheel!

Howard

The M type also had a leadscrew dog clutch with carriage trip mechanism that would have been right handy for repetition production work. Also had a very solid "anvil style" bed that did not need levelling on set up and made it a very accurate lathe.

I dont see the ML4 cross slide screw error as a big deal. Close enough for roughing cuts and on a 2 thou finishing cut the error is only .08 of a thou. Thats .00008" so not enough to worry about on a lathe where normal tolerance is .001" at best.

Indeed, For my use i cant measure more than 0.0005" anyhow so the error is unnoticed unless it becomes accumilated by traversing the cross slide or top slide.

I'm glad that this query sparked off some useful discussion, though my point wasn't intended to do so. Just relaid what id read, and as i said for some reason they had built an error into the lathe.

Thanks for confirming my thoughts regarding the lead screw, at least i know in that direction i only have backlash of the half nuts to worry about, oh and disengaging the banjo from the spindle so i don't break the sheer pin (again), and watching that line so that i don't over cut on the first pass, oh and............. lol

Regards

Jon