myford etc.

hi all,

total beginner here, have a question: is it possible to work in milimeters on the lathes like myford ml7?

thank you

Yes. You can buy metric cross slide and top slide lead screws, nuts and dials for them. Myford sells them. You can also get a metric handwheel to fit on the main leadscrew. It might work out cheaper to just fit metric DRO units.

Metric threads can be cut using the standard imperial lead screw but using conversion gears. Or by following the charts in the book "Screwcutting in the Lathe" by Martin Cleeve to use standard imperial leadscrew and standard gears to cut metric threads.

Of course it is possible. Just that one would need to convert the metric requirements to imperial measurements if one wanted to use the scales on the machine slides. One can measure a length (or any other dimension, for that matter) in any chosen units. It is internationally accepted to use S.I. units these days. Only the USA and a very few other places continue with non-metricated units - but there are a lot of lathes, etc, still around with imperial scales, and quite a lot of the older generations still stuck with the old system (even personal height, weight measurements by younger people who don't actually learn the feet, inches, stones, pounds and ounce systems at school!)

It is interesting to note that final sizing is normally measured by a separate instrument (micrometer) and these are at the choice of the user. Even if using a dro, measurements of items produced will still be checked at least occasionally by micrometer, etc.

One good reason for modellers, making items faithfully to scale, is that the orignal '12" to the foot' models were all made in imperial units in the UK, and there are easily scaled (in the main) to 1/2, 1/3, 1/4, 1/6 of the original.

Even the american system is usually worked in thousandths of an inch, even if they start out a 1/4, 1/8, 1/16, 1/32, 1/64 etc!

As NDIY says one way is to buy yourself a digital metric/imperial set of calipers or micrometer and use the in-built function

...but if you want to keep the grey cells working I have found that it's just as easy to buy yourself a metric micrometer or even just continue to work in metric and as you're approaching the correct dimension in diameter or length multiply the amount you need to remove in mm by 40 to give you the number of 0.001" (thousandths) you need to take off using the dials - Simples.

The actual conversion is slightly less at 39.37008 but since cuts of more than a mm or two (in diameter) on a Myford lathe can be challenging it's close enough and when you get below a mm the approximation is pretty good.

Once you get the hang of it, it becomes second nature to multiple by 4 and shift the decimal point appropriately.

[Edit: I have an imperial mill and an imperial lathe and work in metric often - It's no bother at all. For the Myford ML7, I bought two 21 tooth change wheels from RDG which give access to almost all of the usual metric pitches - within a gnats piccolo of the correct one and probably well within the accuracy of my worn old feed screw.]

HTH

Jon

Edited By Jon Gibbs on 07/11/2017 09:13:00

Hi Vladimir

In regard to turning, the lathe is probably the least problematic machine for working in duel measuring systems either metric on imperial or imperial on metric. The reason being that slideway micrometers indicate how much you machine off rather than being set to aboslute diameters or lengths and that amount is rarely whole numbers anyway.

Digital mics or calipers can readily be set to the required dimension in say mm, zeroed and switched to imperial. Subsequent measurement of the workpiece will indicate how much is required to be machined off the part and measurements will be in the same units as your imperial lead screws.

The main issue for imperial lathes such as the Myford is cutting metric screw threads which can be done but requires generally more complex change wheel set up's or additional equipment on gearbox machines. For most smaller threads you are going to be using taps and dies rather than screwcutting in any case.

The addition of Digital Read Out units obviously makes the slides at least 'ambidextrous' in that you get to choose the units and have no requirement to look at the micrometer dials at all.

Similarly DRO's render Milling machines duel metric and imperial (ambidextrous) and in my opinion are much more to be desired as absolute position from an edge or edges is exteremely usefull.

You can convert slide lead screws but personally I would not bother when there are other ways round the problem and you can bet your boots that the next project you wish to do is going to be in the system of measurement you have just swapped from.

So buy yourself a decent digital measuring kit and get turning.

Best wishes Martin

I agree with Jon. The real way to resolve it is to become so familiar with both systems that conversion with adequate precision for the job just becomes a simple mental flip, and for final cuts the 40 thou per mil rule of thumb works fine except in rare instances.

However, the obvious trend in design and available tooling is towards metric, so if you're sure you want to follow that, metric components as Hopper said are available. The Myford Speed 10 I had for 15 years was already metric, and presumably other models like the 7 series can be had in metric too.

If you only use the dials for putting on a cut, then letting 1 thou approximate to 0.025mm will do for most things.