Myford Ml7 Technical Drawings

[Harry BroadbentParticipant @harrybroadbent75717]

Is there any interest in having the technical drawing for every part on the Myford ML7 lathe. the drawings would be a Pdf in millimeters. a lot clearer and easier to follow than the current ones on the Myford website.

This would allow people to machine there own parts to go onto the Myford ML7.

[Harry BroadbentParticipant @harrybroadbent75717]

[DC31kParticipant @dc31k]

Posted by Harry Broadbent on 15/09/2023 12:53:26:

…the drawings would be a PDF in millimeters.

a lot clearer and easier to follow…

Making drawings in millimetres of parts which have always been imperial rather negates the 'clear and easy to follow' idea.

If by 'every part' you include the fasteners, what will be your metric description of a 2BA x 1/2" long socket capscrew?

[JasonBModerator @jasonb]

Probably the same way I would put a pipe thread or UNEF spark plug thread on a metric drawing.

That's the same way someone may put a M10 x 1 spark plug thread on an imperial drawing.

Edited By JasonB on 15/09/2023 20:37:37

[Nigel Graham 2Participant @nigelgraham2]

It would be much clearer and more logical to make all the dimensions Imperial but with decimal rather than vulgar fractions, and the fastenings all BS or BA, since if you make accessories for a machine built to British dimensions it is easier and much better practice to make them conform to the machine itself.

If you are making accessories for a Myford ML7, it is very likely you will be turning the parts on the said lathe, which was normally fitted with inch-fraction lead-screws and calibrated in thous.

Keeping the fastenings consistent also avoids the bad situation of needing three ranges of spanners for operating and servicing it! (Some of the commercially-sold Myford stuff now seems to have various inconvenient hexagon sizes.)

If constructors wish to use a rare ML7 fitted with metric screws and dials then obviously they'd need convert the drawings to mm; but printing the drawings in mm means most users will have to convert all the turned sizes to decimals of inches anyway.

[duncan webster 1Participant @duncanwebster1]

I hesitate to point out the obvious, but BA is a fundamentally metric concept. 0 ba is 6mm OD, 1mm pitch and then there is a geometric progression.

[Ady1Participant @ady1]

It depends on the people you aim at

An imperial set would be for the more purist traditional customers, and there are a lot of them

10ths sounds like good solid advice (decimals) and modern measuring kit uses decimals

A metric set would suit more practical off-the-shelf get-it-done people

I'm happy to bang off the shelf metric stuff into my myford-drummond gear but there may be a faint sound of wailing and gnashing of teeth from the ghosts of bygone past

Edited By Ady1 on 15/09/2023 23:52:24

[JasonBModerator @jasonb]

If producing the drawings with CAD then why not put dual decimal dimensions which will suit the oldies and also the newer owners who have been brought up with metric

[Nigel Graham 2Participant @nigelgraham2]

Duncan –

True, and I think BA was based on the Swiss, Thury thread, though codified in British Standards in inches. The larger fastenings on Myford lathes are BSF or BSW though, so true rather than derived. inch fractions.

.

Ady-

Nothing to do with "purist traditonal", while if your are a "practical get it done type" you will be able to use both systems. (I use Imperial or metric according to what I am making for what purpose.)

.

Jason –

"…. suit the oldies…"

You youngsters…..

Suit those who will be making the parts on the same lathe with inch-pitch lead and feed screws and decimal-inch dials, more like…..

Nothing to stop you measuring the original made in inches, directly in mm and making the accessories to fit but themselves measured in mm, if you are using another machine that is metric or has a dual-range DRO, but you'd be working to irregular numbers.

[DC31kParticipant @dc31k]

Posted by JasonB on 16/09/2023 06:52:44:

…which will suit the oldies…

I think the emotion and value-judgement-laden language may be a little inappropriate (see also 'purist traditional' above).

From a purely technical, engineering standpoint, it just makes sense to dimension in the units in which the items were originally produced.

It might be a good service to then show alternate dimensions in the measurement system in common use today, but then their origin is clear and nothing is hidden.

I do not know how it would work, but for some things (e.g. counterbores, clearance holes), strict adherence to the original when showing metric might make things more difficult to construct. I guess a lot depends on the skill of the person making the drawings in choosing a suitable substitute.

[Nigel Graham 2Participant @nigelgraham2]

Holes for screws are not too problematical because many screw-thread charts show tapping and clearance diameters in mm anyway for metric, BS and American screws; suiting the commonly-available drill sets made to 0.1mm (~0.004" ) increments.

Whether I use inches or mm, I try to use nice round numbers, even for inch-fractions; especially for something entirely new.

The one to watch is a counterbore intended for a socket-spanner rather than a socket-head screw, and clearance for the appropriate spanners generally. 

The biggest bug-bear in model-engineering has anyway been the way drawings' dimensions have long been laid out, not their units. Though sticking to vulgar fractions even for parts intended to be made on decimally-calibrated machine-tools (mm or inch) parts is a secondary nuisance.

Edited By Nigel Graham 2 on 16/09/2023 08:00:05

[John HaineParticipant @johnhaine32865]

I have a S7 but can't see any need for a set of engineering drawings. The main dimensions of interest are for interfacing accessories, usually to the spindle nose or carriage, and they can be measured in a trice. Likewise individual parts. Interesting that everyone leaped into the debate about dimensions and threads without answering the initial question!

Mind you, I suspect that Myford might like an accurate and detailed CAD model!  I wonder what state the "original" drawings are in?

Edited By John Haine on 16/09/2023 10:36:15

[duncan webster 1Participant @duncanwebster1]

Posted by JasonB on 16/09/2023 06:52:44:

If producing the drawings with CAD then why not put dual decimal dimensions which will suit the oldies and also the newer owners who have been brought up with metric

I'm fairly old (73) but find metric much more user friendly.

[JasonBModerator @jasonb]

I suppose drawings would be usefull if you had a basket case lathe where parts were missing or badly worn so you may not be able to take your own measurements and you had the means to make replacements. Would be interesting to know what fits and finishes, material specs, heat treatments, etc might be on this new drawing set unless you knew what were on the Myford originals were that may be a problem.

[Ady1Participant @ady1]

Drawings are useful if you want to do your own upgrades or see how an add-on project will interact

You do however need CAD skills in the first place to take full advantage of it

Handy for missing bits too, as Jason said

Saves you going into the workshop and scrabbling about

[Harry BroadbentParticipant @harrybroadbent75717]

I know the cast parts can be hard to get hold of for a reasonable price so I’m thinking it’d be useful to produce an STL file for each part. This can then be 3d printed and cast at home with aluminium. In addition the cad file would help people to make there own after market upgrades and mounts for various things like guages. It’s just a thought as I am doing it for myself and wondered if it would be something people would be interested in for a few quid.

[Mike PooleParticipant @mikepoole82104]

As Myfords are imperial machines then dimensions in metric will throw up some awkward figures and some rounding if the accurate conversion is not used. 1/64” is 0.396875mm or 0.015625” . The problem with rounding dimensions is that the errors can accumulate. Is your idea to produce a dimensioned and toleranced drawing to make a part to original spec. or just a general drawing with dimensions? I would think most people would be fitting the parts to their machine so just the nominal dimensions would be adequate.

Mike

[Harry BroadbentParticipant @harrybroadbent75717]

Yes there would be geometric tolerancing and Limit tolerances fir critical dimensions. Most likely follow the iso limits and fits for mating parts

[Nigel Graham 2Participant @nigelgraham2]

Mike –

I think your last sentence summarises it admirably!

Harry –

We all do our best to produce decent-quality work as accurately as we can but model-engineering has never worried about stating tolerances and formal standards on drawings because we make things to suit our workshops and our own skills, for ourselves, not for interchangeable production; so tend to be fitter-turners rather than production-machinists.

Obviously we should and usually do endeavour to make, for example bearing-race fits as specified for the bearing types, O-ring and circlip grooves to the manufacturers' recommendations, etc., and these are not difficult to find (often from the part makers); but not all of us have full, ISO9001-registered metrology facilities.

By all means put those dimensions on the drawings, as they should be; but a model-engineering workshop drawing does not need meet full, formal ISO industrial standards. It's more important that the drawing is clear and unambiguous, the details and dimensions are correct and the parts made to them do actually fit each other. (If it's any comfort, even professional trade draughtspeople occasionally make mistakes – or design details that work as CAD images but can't be made!)

[David-Clark 1Participant @david-clark1]

Clear drawings with measurements in either metric or imperial. I was born well before metrication but have never had a problem using either system mainly because I was interested in model railways for most of my life which in my case was scaled at 4mm to a foot so metric comes easily to me.

[Nigel Graham 2Participant @nigelgraham2]

Why has your post appeared twice? This seems to happen fairly often (with different people!).

Likewise though – I am used to both metric and imperial but by work rather than the inch-based model-engineering.

Many of the trade drawings I encountered carried tolerances of +/- 1/64 for fractions of inches, but 0.01 or 0,005 inch for decimal, u.o.s; depending on the dimension's function. I forget the mm tolerances but 1/64" = 0.4mm.

I used metric measurements and fastenings for the travelling hoist I built for my 16-foot X 6 ft workshop – after all the materials all came in mm sizes and this is a new item not a scale model, part of the workshop equipment.

On the other hand my model steam-wagon is in inches as the original was English-built more than 110 years ago – though contains an unfortunate mixture of BS and BA with Metric fasteners. This is poor practice, I know, although sometimes for reasons like simulating rivets or to be stainless-steel.

Similarly I try to make any machine-tool accessories compatible with their host machine, be they of metric or Imperial dimensions, including threads.

The original question though was about drawings for fittings for Myford ML7 lathes, and many tools and accessories for, or designed to be made on, these lathes, have already been published in ME and model-engineering reference-books over many years. So new ones are unlikely to be at all "new" even if you suggest alternative materials or dimension them in millimetres.

The original machines were all built to inch sizes so while some constructors may well prefer to make fixtures and fittings in mm, at least some important dimensions need match inch-based ones on the lathe: spindle and tailstock diameters, the T-slots, bed, etc. So somewhere along the line someone needs convert them, be that the designer or the maker; and the conversions either way will not be nice neat integers.

In making the drawings, it matters not a jot whether CAD or manually drawn as long as they look proper but more importantly, are clear and free from frustrating mistakes!

It may be possible to transmit a CAD file to the buyer electronically – but he needs the same or compatible CAD software and a printer for the drawing's A-number sheet size. Squeezing drawings created for an A2 or A3 sheet onto A4 for example, risks dimensions and other annotations, and fine details, too small to read. I'd rather buy paper drawings in their proper sheet sizes, from the start.

[David-Clark 1Participant @david-clark1]

Hi Nigel

I did not post twice and I can't see how to delete it.

[Nigel Graham 2Participant @nigelgraham2]

It happens fairly often on different fora so must be some quirk of how the site works.

[JasonBModerator @jasonb]

More often a slow connection or fat fingers at the poster's end.

[David-Clark 1Participant @david-clark1]

Hi Jasonb 1,000 gb connection so not speed. Fat fingers possibly but I usually use a stylus.

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