Myford ML4 leadscrew dials

I hear ya. I really miss the M Type's dog clutch when using my ML7 and have to pull the gear off the leadscrew to free up the leadscrew to use the graduated handwheel. So much so that i plan to make and fit a dog clutch to the ML7.

Edited By Hopper on 11/06/2020 09:46:45

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Just a thought ...

The approximation is reasonably expedient for those working to decimal drawings

... Not dissimilar to the situation we currently see with some ‘Metric’ lathes.

So the underlying question might be:

When those early Myford lathes were first made, was anyone using twelfths of an inch ?

MichaelG.

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[*] remember that twelfths survived for a long time on school rulers, and that both ‘twelfth scale’ and 1:144 remain common.

I've never seen 12ths used -- so they must be ancient. Quite possibly explains it though. Those early days they did a lot of turning with a rule and calipers. Micrometer? That were luxury that were.

Twelfths:

Is there an indirect link with pounds, shillings and pence?

Twelve is a useful number for dividing purposes.

1/12 scale is useful for modelling things like locos, traction engines etc, since it is 1 inch to the foot.

But since machining is carried out in decimal units, we usually work in Imperial units, such as thous or millimetres in Metric.

The only "incomplete" decimal dial that I have ever made was for a 16 tpi leadscrew. The final half size interval of 62.5 on the handwheel looks strange.

Howard

I think you're barking up the wrong tree here chaps. Pre-war, most amateur lathes had no micrometer dials on any of the feeds. Readers of Model Engineer would have worked to 1/64ths using a rule and a pair of old school calipers. Even the Admiralty Drummond M type shown on Tony's site doesn't obviously have any dials as original fitments. LBSC used to ream his loco cylinders and would have made the piston fit with graphited yarn packing.

Stay well,

Rod

Not necessarily - The pictures on Lathes.co.uk show Drummond M Types with cross slide dials, but not top slide, while quite a few of the Myford ML series have both. These may have been post war additions of course, but it certainly was possible.

I suggest that no one would design a lathe intended to have a micrometer dial with a 12 tpi screw. Possibly, as time went on and devices to measure diameters to 1 thou became affordable, then the manufacturers (and possibly end users) fitted "good enough" dials to their existing designs.

Rod

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That seems very reasonable, Rod ... but the question remains: Why use 12 tpi ?

MichaelG.

If you are not bothered with a micrometer dial then why not? For the lead screw on an imperial lathe then the choice is really 8, 12 or 16. For a light lathe then 12 is probably a good compromise. It probably also gives a good compromise on speed of traverse and feel on a cross slide. But all these pre-war lathes evolved so I am not sure there is necessarily a logical answer.

Rod

Edited By Roderick Jenkins on 11/06/2020 18:14:39

This document contains two brochures for ML series lathes. **LINK**

The first has the explanation that micrometer dials were standard and they are clearly fitted in the pictures whilst the second, presumably earlier, has no mention or dials shown in images.

Nick,

Interesting brochures, thanks for the link.

Rod

1930s M Types had a cross slide graduated dial in 1 thou increments. None on the top slide or main leadscrew handwheel though. But you can get pretty close by 'feel' , knowing what 1 full turn gives .125" on the leadscrew and advancing 1/8 of a turn etc.

Hi Jon

With reference to your original post, if you fit a leadscrew dial do make it adjustable so it can be zeroed before use.

I put a fixed dial my M many years ago and whilst it has been very useful it is sometimes a pain marking pencil lines on the dial and doing mini calculations to make adjustments.

Geoff

Very good point. Having them fixed as you say can sometimes be tricky, While been able to reset the dial on the fly is certainly handy. The ones id seen where only fixed, marked off on the hand wheel boss itself.

I've been enjoying reading the posts put forward with regards to the cross slide and compound leadscrews. I didnt think that my comment would have the reaction it has. I did think it was common knowledge but having thought about it i couldn't tell you what the thread was in another other lathe.

Jon

Picking up on Rod's point, very old lathes did not have dials. The craftsmen knew their machines and worked from pencil lines or chalk marks on the plain diameter of the handle. They worked by feel, with callipers, and steel rules, making one part to fit another. Interchangeability became a necessity with mass production, driving the need for repeatable dimension.

My turning instructor could work to within a few thou with a 6" steel rule, whilst I relied on the micrometer dials!

Howard.