Myford ML7 – Convert from Imperial to Metric

[chris jParticipant @chrisj]

Hiya

I hope this hasn't been done before but I coudn't find it.

As the title suggests, I would like to convert my new lathe to metric.

Has anyone done this ?

[chris jParticipant @chrisj]

[James BParticipant @jamesb]

Hi Chris,

You would be looking at replacement feedscrews and nuts for crossslide and top slide, plus the dials of course. For screwcutting metric threads, a new leadscrew and clasp nuts, plus a leadscrew handwheel, if your lathe has one, plus the relevant changewheels.

You might be better off looking at a cheap DRO setup – then you could switch between metric and imperial as you require?

James

Edited By James Burden on 06/07/2012 12:45:20

Edited By James Burden on 06/07/2012 12:47:13

[chris jParticipant @chrisj]

Posted by James Burden on 06/07/2012 12:44:11:

Hi Chris,

You would be looking at replacement feedscrews and nuts for crossslide and top slide, plus the dials of course. For screwcutting metric threads, a new leadscrew and clasp nuts, plus a leadscrew handwheel, if your lathe has one, plus the relevant changewheels.

You might be better off looking at a cheap DRO setup – then you could switch between metric and imperial as you require?

James

Edited By James Burden on 06/07/2012 12:45:20

Edited By James Burden on 06/07/2012 12:47:13

That's not a bad idea, what would one cost whould you think ?

[blowlampParticipant @blowlamp]

Aren't the leadscrews and clasp nuts all imperial, regardless of the lathe's metric/imperial status?

Martin.

[Russell EberhardtParticipant @russelleberhardt48058]

I don't see the point. You can cut metric threads with the appropriate change wheels. When turning to a metric size set your digital vernier to the (metric) size you want. Zero it, switch to imperial and it will tell you directly how many thou to take off the diameter.

You can make a cheap DRO setup from digital verners as well.

Russell

[chris jParticipant @chrisj]

Posted by blowlamp on 06/07/2012 13:08:00:

Aren't the leadscrews and clasp nuts all imperial, regardless of the lathe's metric/imperial status?

Martin.

Wish I knew Martin

[Ian S CParticipant @iansc]

For the leadscrews, if you must you could make up new dials, on my Taiwanese lathe they are calibrated in both, but digital would be the way to go, and a metric convertion gear for screw cutting, the only thing is the screw cutting dial becomes redundant on metrics, but not a great problem. Ian S C

[chris jParticipant @chrisj]

Posted by Russell Eberhardt on 06/07/2012 13:16:49:

I don't see the point. You can cut metric threads with the appropriate change wheels. When turning to a metric size set your digital vernier to the (metric) size you want. Zero it, switch to imperial and it will tell you directly how many thou to take off the diameter.

You can make a cheap DRO setup from digital verners as well.

Russell

Do you know what the wheels I would need are, I think it's 2 x 21 tooth but I'm not sure

[chris jParticipant @chrisj]

Just in from Myford by email

++++++++++++

To convert your ML7 lathe to metric, you will need:

Metric feedscrew & nut for top slide

Metric feedscrew & nut for cross slide

Metric leadscrew handwheel

Metric Tailstock Barrel

Metric micrometer dials (for the cross AND top slide)

[chris jParticipant @chrisj]

Oh and here is the change wheel info

Link

[Another JohnSParticipant @anotherjohns]

As I do 100% metric, for my larger Kerry 1124 lathe, I just have some 0-25mm dial indicators on the cross slide and the top slide.

One of these days I'll DRO it, but it's done at least 10 years this way just fine.

The dial indicators are held on by strong magnets taken from older computer disc drives.

I only cut metric threads on it, and the change wheels for metric were supplied.

It's quick and easy – think about doing the dial indicator route for now.

Another JohnS.

[chris jParticipant @chrisj]

Posted by John Alexander Stewart on 06/07/2012 13:52:29:

….

It's quick and easy – think about doing the dial indicator route for now.

Another JohnS.

Any chance of a picture of what you have done John

[Ady1Participant @ady1]

DRO the slides, digital calipers cost a tenner, and get the changewheel setup for threading purposes

[Another JohnSParticipant @anotherjohns]

Any chance of a picture of what you have done John

Not until tomorrow at least.

But, cross slide:

– magnet to apron, square alu section horizontal on magnet.

– dial indicator on square alu section, plunger pointing to centre of lathe, along cross slide, tailstock side (behind toolpost).

– rod, through 2 bushings and thumbscrew so it is adjustable, on cross slide, on the tailstock side of the cross slide, pointing in/out, across lathe axis.

– both dial indicator and this rod are "horizontal". dial indicator rests on end of rod. Thumb screw on rod allows for adjustment. Rod resides permanently on cross slide, dial indicator comes off if required.

compound rest:

– dial indicator on aluminum square section, mounted so dial is flat, and plunger facing headstock;

– "rod" mounted on small magnet attached to base of compound rest, adjusted to hit plunger.

So, both dial indicators are horizontally mounted, dials facing up. Both plunge onto rods on cross slide, or compound rest base.

Because of the magnets, if there is a "crash", the dial indicator comes off with magnet from lathe; so far no issues.

I realize that this is an 1124 lathe; 5-1/2" centre height. However, I have been known to do similar to my Emco Compact-8, so you should have room on a Myford.

Yes, I have only 25mm movement, but that has never been an issue so far.

Yes, a DRO would be better. But the price was right, and it's been great working in metric on this old lathe.

Another JohnS

[chris jParticipant @chrisj]

Posted by John Alexander Stewart on 06/07/2012 15:58:21:

Any chance of a picture of what you have done John

Not until tomorrow at least.

But, cross slide:

– magnet to apron, square alu section horizontal on magnet.

– dial indicator on square alu section, plunger pointing to centre of lathe, along cross slide, tailstock side (behind toolpost).

– rod, through 2 bushings and thumbscrew so it is adjustable, on cross slide, on the tailstock side of the cross slide, pointing in/out, across lathe axis.

– both dial indicator and this rod are "horizontal". dial indicator rests on end of rod. Thumb screw on rod allows for adjustment. Rod resides permanently on cross slide, dial indicator comes off if required.

compound rest:

– dial indicator on aluminum square section, mounted so dial is flat, and plunger facing headstock;

– "rod" mounted on small magnet attached to base of compound rest, adjusted to hit plunger.

So, both dial indicators are horizontally mounted, dials facing up. Both plunge onto rods on cross slide, or compound rest base.

Because of the magnets, if there is a "crash", the dial indicator comes off with magnet from lathe; so far no issues.

I realize that this is an 1124 lathe; 5-1/2" centre height. However, I have been known to do similar to my Emco Compact-8, so you should have room on a Myford.

Yes, I have only 25mm movement, but that has never been an issue so far.

Yes, a DRO would be better. But the price was right, and it's been great working in metric on this old lathe.

Another JohnS

John, Did you get a chance to take a couple of pictures ?

[John Stevenson 1Participant @johnstevenson1]

Posted by chris j on 06/07/2012 13:48:02:

Just in from Myford by email

++++++++++++

To convert your ML7 lathe to metric, you will need:

Metric leadscrew handwheel

How can you fit a metric handwheel to an 8 tpi leadscrew ?

And this from Myford ???

John S.

[chris jParticipant @chrisj]

Posted by John Stevenson on 08/07/2012 21:11:10:

Posted by chris j on 06/07/2012 13:48:02:

Just in from Myford by email

++++++++++++

To convert your ML7 lathe to metric, you will need:

Metric leadscrew handwheel

How can you fit a metric handwheel to an 8 tpi leadscrew ?

And this from Myford ???

John S.

To be honest John, I don't know.

Hence the posting and asking questions.

It was direct from Myford

Chris

[John HaineParticipant @johnhaine32865]

I have a metric super 7. The X-slide and topslide have 2 mm pitch feedscrews. The T/S has a barrel with a mm scale. As I found out to my cost one day, the leadscrew is still 8 tpi! 8 tpi is 3.175 mm, so the scale on the handwheel is calibrated in mm up to nearly 3.2 then goes back to zero! As it doesn't have a zero-settable thimble the graduation is next to useless. Even if it did it would only be useful up to 3.175 mm.

For metric screwcutting, Myford provide tables of approximate ratios that are good for some common metric threads which are just fine for shortish fasteners but obviously if you want to make a metric measuring screw they aren't and you need a 127 tooth change gear (which can only be fitted with some difficulty). However since almost all the threads we cut are for fastening the approximations are not a problem since the errors are almost certainly less than the machine accuracy anyway.

I have converted to CNC so the imperial L/S isn't an issue, it's all sorted out in the software.

J.

[Clive HartlandParticipant @clivehartland94829]

John, I have the same sort of fixed scale on the ML10, what I do is set the Lead screw scale at '0' and then feed in the top slide and tool to touch the work and then I can advance the Lead screw using its scale.

I appreciate the problem of the odd markings of the scale against the lead screw pitch but a '0' mark is always useful when working repetition jobs.

I have wracked my brains to see if I could make the lead screw scale a, 'slipping scale' but it would mean a complete re-work and making of a new mounting boss.

The problem is getting the scale off as a ring but then mounting it on another part to allow 'slipping'

Clive

[chris jParticipant @chrisj]

I'm begining to wonder if it is worth the trouble to worry about it.

Perhaps change the gearing on the lead screw but leave the top and cross slide as they are and fit a DRO of some kind.

Thanks for all your replies by the way.

[Ady1Participant @ady1]

Perhaps change the gearing on the lead screw but leave the top and cross slide as they are and fit a DRO of some kind

—-

Fit a 10 quid DRO to your cross slide one evening and be amazed

The Digital vernier I use switches off automatically, stores the reading and uses AG13 poundland batteries

It's the best simplest most useful mod you will ever make

 

 

The biggest problem is drilling the stainless jaws, they are TOUGH, you will need to drill them with carbide

http://www.model-engineer.co.uk/forums/postings.asp?th=55550

gl

 

Edited By Ady1 on 09/07/2012 09:40:36

[pierre ehly 2Participant @pierreehly2]

Hi,

For the lead screw (8tpi) myford table are usable aproximations

Exact (exeption from your LS error/wear) conversion is obtained with a 127T wheel

A very good translation is made with 47/37 (1,27027) this gear train is more handy

as the big 127T wheel.

By adding this gear train at the end of the lead screw (TS side) you can obtain a

handle rotation 1 turn = 3mm.

Is is also neccessary to graduate the handle with an appropriated graduations

(75,100,150,300)

As the Xslide & topslide are 10tpi pitch for imperial & 2mm pitch for metric, 100 divisions

give 0,001" & 0,02 mm. So the dial can remain the same in both case.

Owner of ML7 Sn° K37512

pm

[Ady1Participant @ady1]

IMO guys like Sparey Bower and Westbury would have jumped at DRO had it been available

One unforseen handy thing about a saddle DRO is that once you have set up the lathe for screwcutting you can advance the saddle a set number of headstock revolutions, the TPI of the thread you want to cut, and see if things are going to work right, since the DRO should read 1 inch, 2 inches etc

DRO is independent from the machine

This also makes resetting a cut easier too, because a DRO is not affected by any cross slide backlash

So resetting a screwcutting operation to +2 hundredths of a mm becomes a doddle

 

Wish I'd done it from the start

Edited By Ady1 on 09/07/2012 09:59:55

[Ady1Participant @ady1]

One unforseen handy thing about a saddle DRO is that once you have set up the lathe for screwcutting you can advance the saddle a set number of headstock revolutions, the TPI of the thread you want to cut, and see if things are going to work right, since the DRO should read 1 inch, 2 inches etc

——

It also occured to me that if you needed a really accurate long thread and your leadscrew was old and worn a DRO would tell you what your best configuration was

A change by a single wheel tooth to a "wrong" setup might actually be more accurate over the full length of the cut

so 20-73/40-60/40-50 would be better as 20-72/40-60/40-50 because of machine issues over the length of the cut

Might only be useful to a real professional btw, but it's still handy to know

Because DRO is an INDEPENDENT measuring system I got options which never occured to me until I fitted it

Edited By Ady1 on 09/07/2012 10:22:19

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