Myford ML4 headstock thread size

[StevegParticipant @steveg18231]

Hi

I need a new 4 jaw Chuck for my myford ML4

but I have no idea what size or thread it is.

can anyone advise please?

thanks

[StevegParticipant @steveg18231]

[OldironParticipant @oldiron]

Maybe some info here >>ML4

regards

[GeorgineerParticipant @georgineer]

Myford used three different spindle nose threads for the ML4, all Whitworth profile:

Earlier ones were 7/8" x 9tpi or 7/8" x 12 tpi.

Later ones were 1 1/8" x 12 tpi, the same as the ML7 but with a smaller register diameter ( 1 1/8" instead of 1 1/4" ).

Mine has a non-standard mandrel with a 7/8" BSF thread of 11 tpi. It's a jungle out there!

George B.

(edited to remove the blasted smiley which the software added.)

Edited By Georgineer on 08/02/2021 18:11:19

[StevegParticipant @steveg18231]

That links takes me to YouTube and a ship video?

[StevegParticipant @steveg18231]

Thanks George but how do I find out the year of mine?

id read 1 1/8 x12tpi but unsure.

[GeorgineerParticipant @georgineer]

Posted by Steveg on 08/02/2021 18:04:16:

That links takes me to YouTube and a ship video?

Me too. I think that my post was better!

George B.

[GeorgineerParticipant @georgineer]

Posted by Steveg on 08/02/2021 18:05:58:

Thanks George but how do I find out the year of mine?

id read 1 1/8 x12tpi but unsure.

No reliable way of telling the year – for many years the ML1, 2, 3,& 4 had no serial numbers, and I don't think anybody has a register of the ones that did. Your most reliable option is to unscrew the existing chuck and measure what you've got.

George B.

[StevegParticipant @steveg18231]

Posted by Georgineer on 08/02/2021 18:09:21:

Posted by Steveg on 08/02/2021 18:05:58:

Thanks George but how do I find out the year of mine?

id read 1 1/8 x12tpi but unsure.

No reliable way of telling the year – for many years the ML1, 2, 3,& 4 had no serial numbers, and I don't think anybody has a register of the ones that did. Your most reliable option is to unscrew the existing chuck and measure what you've got.

George B.

So the next question is how do I measure it?

[OldironParticipant @oldiron]

Posted by Georgineer on 08/02/2021 18:06:22:

Posted by Steveg on 08/02/2021 18:04:16:

That links takes me to YouTube and a ship video?

Me too. I think that my post was better!

George B.

Well I do not know what happened there. ???? It was supposed to link to a forum post. Link

Most strange. But that has been life for the last 12 months

  Just watched the YT video. gets interesting at 2-15

regards

Edited By Oldiron on 08/02/2021 19:05:26

[GeorgineerParticipant @georgineer]

So the next question is how do I measure it?

I presume you have a rule of some sort. To measure the diameter, hold the rule vertical with one edge against the end of the mandrel and look straight at it. It should be easy to tell if the outside diameter of the thread is 7/8" or 1 1/8" – that is, more or less than one inch.

To measure how many threads per inch, lay the rule along the threaded part of the mandrel so the edge touches the crests of the threads. Line up the zero of the rule with one crest, then count how many crests there are in half an inch (I don't think the threaded portion is long enough to do a whole inch). Counting the crest at position zero as zero, you will either count to four-and-a-half (which gives 9 tpi) or six (which gives 12 tpi). Anything else and you're in uncharted territory!

The 7/8" x 9tpi is a standard thread, 7/8" BSW, and my guess is that Myford didn't use it for long because people didn't have to go to them for taps and dies, so they invented the proprietory 7/8" x 12 tpi. If that is what you have, you will find it difficult to get hold of an existing backplate for your chuck, and may well end up having to make your own.

The 1 1/8" x 12 is also a Myford proprietory thread, but was also used on the ML7 so you can buy a new one which will fit, but won't use the register for location. If you don't know what that means, read up about it on line or in books.

There is a lot of information on this forum if you do a suitable search (start with ML4, then ML3, ML2 and ML1 which are closely related). There's more at lathes.co.uk including a description of how to make a backplate.

George B.

[Howard LewisParticipant @howardlewis46836]

Measuring the thread on the mandrel should be pretty easy.

For a British made machine of this vintage it is fairly safe assumption that threads will be Whitworth form, BSW or BSF (On a ML4 you will find both in various places ) measure dimension in Inches, not mm.

Certainly for the OD, use a 6" rule, a mic, or a calliper for the OD of the thread. It will be either 0.875", or 1.125

If 1.125, you can take it that the pitch is 12 tpi.

If it 0.875" then you need to measure the distance between thread crests. The difference beteen 9 and 12 tpi ought to be obvious.

The better way to do it is to use Whit form thread gauges., 9 tpi will be listed as 7/8, 12 tpi as 1/2" probably.

Study the Lathes UK web pages for the Myford ML1, 2,3 and 4.

You will learn a lot from there.

Howard

[Howard LewisParticipant @howardlewis46836]

SteveG,

You are unlikely to find a new chuck with a thread to fit yoiur ML4.

Either you will need to buy a plain backplate and cut a thread and machine it to fit your Mandrel.,before machining it to suit the new chuck, or make an adaptor to match your mandrel thread to the 7 Series thread and possibly register.

You can buy backplates and chucks with thread and register for the later 7 Series machines.

To fit one of these, you will need to make an adaptor, from 7/8 thread to the 1.125 x 12 tpi, thread and register for the 7 Series.

If your machine is one of the later ones with the 1.25 x 12tpi thread, you will need to sleeve the register down form 1.250 to 1.125. Since the sleeve will only be 0.0625 thick in the wall, this might entail boring out the 1.250 register, so thast a sleve with a thicker wall can be made and secured into place, with an anaerobic sealant.

If you choose to follow this route, I would suggest that the boring the register is left as the final operation.

Fit the backplate onto the mandrel, wrong way round, (having already measured your register ), before boring it out to be a snug fit (almost a tight fit ) on the register..

Once the register is completed, the backplate can be fitted normal way round for it to be faced and the OD turned to be a snug fit in the chuck of your choice, before drilling and tapping for the securing setscrews or studs..HTH

Howard

[StevegParticipant @steveg18231]

George B and Howard,,

thank you gentlemen for your expertise it’s very much appreciated!

I shall look into this and hopefully get the information I need using your methods.

thank you

ill update this thread as soon as I’ve done the measurements.

[StevegParticipant @steveg18231]

George b and Howard

the diameter is 1 1/8 and over a 1/2” distance I have counted 6 crests so am I right in thinking

that my spindle thread is the 1 1/8” x 12tpi?

[Howard LewisParticipant @howardlewis46836]

Yes, it sounds like you have one of the later Mandrels.

Good news in that you can buy ready machined backplates, or chucks with the standard 1 1/8 x 12 tpi thread.

The bad news is that these will have a 1 1/4 register, so you then need to turn up a plug to fit securely into the 1 1/4 register., so that it can be bored out to 1 1/8. Put a small lead in chamfer (say 0.010 – 0.015" ) on the end that will first go into the register on the 4 jaw.

Now comes the Catch 22 moment. But all is not lost.

My suggestion:

Measure, as accurately as possible, the diameter of the register on your Mandrel, and note it.

Turn up a plug so that it has 0.001" interference in the register for your 4 jaw chuck (Measure it! )

Put a piece of bar, at least 3/4 " diameter, into the 3 jaw chuck and turn it down so that it just cleans up for a little more than the length of the jaws of the 4 jaw chuck.

Clamp the 4 jaw chuck to the turned diameter with the register facing outwards. (i e Jaw to jaw more or less, but with the 4 jaws only on the turned diameter. This turned diameter will be concentric with the Mandrel )

Clock the register, and adjust the jaws of the 4 jaw until the register runs as true as you can get it (Within 0.0005" would be my target ) While you are doing this, put the plug into the freezer, and leave overnight.

Once you are happy with the concentricity of the register, Remove the plug from the freezer and immediately pull / drive the the plug into the register, which has been coated with a high strength Loctite or similar anaerobic retainer. Leave the anaerobic to cure for at least 12 hours, before drilling / boring it out to (The dimension of the lathe Mandrel + 0.001" ) If needed, face the sleeve to length, and make a small internal chamfer, (Again 0.010 -0.15" ). The sleeve is going to be only 1/16 " wall thickness, so take things very gently. during the drilling, boring and chamfering.

HTH

Howard

Better to spend too long on these operations than to save time and pull the sleeve loose! Also, you don't want to produce a lot of heat which might degrade the anaerobic.

Hopefully you should now have a 4 jaw chuck which will be snug fit on the Mandrel of your lathe.

In reality, with a four jaw you could have a fit which is a little more slack than a 3 jaw, but the looser the fit, the greater the risk of something moving during machining after you have clocked it concentric in the 4 jaw chuck!

So better not to take the risk.

HTH

Howard

[OldironParticipant @oldiron]

Just an addition to Howards post if I may. After you drive the plug into the register do not remove from the chuck or mandrel until you have finished all the operations.

regards

Edited By Oldiron on 10/02/2021 19:07:06

[StevegParticipant @steveg18231]

Thanks gentlemen but being of limited knowledge this has gone over my head.

its not just a matter then of buying a 4 jaw Chuck with the correct 1 1/8 x 12tpi back plate and screwing it on?

[Howard LewisParticipant @howardlewis46836]

I would be amazed if a new chuck or a backplate with a 1 1/8 x 12 tpi thread was commercially available.

You are looking for spares for a machine that is nearly 80 years old!.

The ML4 went out of production in about 1944. And was superceded, post war by the ML7 in 1947.

The best that you will get are either secondhand parts (which may be worn or damaged ) or modern parts that can be modified to fit.

For such a machine there is no "Make or Buy" choice, apart from any used components.

"Make" is about the only option.

The last ML4 with which I had contact, about three years ago, needed a gear cover. It was made out of sheet Aluminium made alongside it, I managed to modify a gear for a ML7 to be used on it!

To make fitting a 4 jaw chuck to it (A n even older machine with the original 7/8 x 9 BSW Mandrel, so possibly 90 years old ) I made an fitting to go on the Mandrel so that a "modern" Myford chuck could be fitted.

Comparatively speaking, only needing to sleeve such a chuck, you are lucky!

Making such parts will be a useful learning exercise for you, and familiarise you with both the machine and machining processes. As would making accessories such a Centre Height Gauge, to aid setting tools in the toolpost. So would making a mandrel Handle, for when you start using Taps and Dies to cut threads.

If you have no books on machining, may I suggest buying and studying:

L H Sparey "The Amateur's Lathe" Basic, principles, leaning towards the ML7 in the illustrations, but still useful.

Ian Bradley "The Amateur's Workshop" Basic principles, of Fitting as well as lathe work

Tubal Cain "the Model Engineer's Handbook". An extremely useful reference book, with data on all sorts of aspects that you will encounter as a machinist.

You will find a set of Zeus Charts invaluable. I constantly still use mine, dating from 1958.

As you find a need for them, you can buy some of the books in the "Workshop Practice Series". Various ones deal with things such as Tool Grinding, or Taps and Dies; and many other things with which a Model Engineer may come in contact at some time.. You are unlikely to need all of them.

Or you could also buy Harold Hall's book "Lathework" It will deal with more modern machines than yours, but the principles remain the same, even if the detail differs.

A while ago, Neil Wyatt ran a short series in Model Engineers Workshop, on Lathework. The machine shown there was a modern machine, a Sieg SC4, much more sophisticated than a ML4 but obeying many of the same rules.

I have had these books, for years, and refer to them from time to time, some more frequently than others, but ALL useful info.

Howard

[GeorgineerParticipant @georgineer]

SteveG,

You have the most useful thread of the three, you lucky man!

If you look at the spindle nose you will see there is a length of thread, and then a plain bit next to the collar. The plain bit is called the register, and is machined very accurately. The purpose of the register is to locate the backplate very accurately, and the thread is made with a bit of slack to allow the chuck to align accurately on the register.

The ML4 spindle you have has a 1 1/8" register, the same diameter as the thread. The later ML7 has the identical thread but a larger 1 1/4" register. That means that your chuck wouldn't screw fully onto an ML7 spindle, but the good news is that any ML7 backplate will screw fully onto your ML4 spindle. However, there would be fresh air between the ML7 backplate and your ML4 register. In this case, the ML7 backplate would be located by the (slightly slack) thread and the contact between it and the flange of the spindle. This is perfectly safe and would be accurate enough for a lot of purposes.

Howard has suggested making a plug to go into an ML7 backplate, to make it fit your ML4 spindle. If I were doing it, I would take the opposite approach and make a sleeve to fit the spindle, converting it to the ML7 fitting. That way, anything made for the ML7 will fit, and a whole world of possibilities is opened up.

The sleeve would need to be accurately machined. (Harold Hall's website has some useful information on how to do this at http://www.homews.co.uk/page133.html ) Howard's suggestion of securing it with Loctite or similar is a good one, as the sleeve will not be subject to big stresses in use. You can get the dimensions you will need from one of the recommended books or the ML7 handbook, which is available on the internet as a scan.

As others have said, there are books and websites full of information, and you will find that as you know more you will know better what to look for and what questions to ask. We are here to help.

George B.

[Howard LewisParticipant @howardlewis46836]

Good Idea, Georgineer!

Having once sleeved the spindle, and skimmed it to correct size, You will have then brought your ML4 upto the normally accepted Myford 7 Series standard. A "Myford" fitting 4 jaw could be fitted and used to set a bar to run absolutely true. The "old" 3 jaw could then be clamped to it and the register opened up to the same dimension as the new sleeve.

The world will now be closer to a oyster than a lobster!

Howard

[StevegParticipant @steveg18231]

Thank you gents,I’ll make a sleeve.

thank you for your help it’s much appreciated.

[GeorgineerParticipant @georgineer]

Posted by Howard Lewis on 11/02/2021 17:41:23:

The "old" 3 jaw could then be clamped to it and the register opened up to the same dimension as the new sleeve.

Ooo, I wish I'd thought of that!

George B.

[StevegParticipant @steveg18231]

For information the 1 1/8 x12tpi Chuck fits perfect without a making a collar

for the register.

[GeorgineerParticipant @georgineer]

Posted by Steveg on 13/02/2021 19:15:01:

For information the 1 1/8 x12tpi Chuck fits perfect without a making a collar

for the register.

As I mentioned earlier, this is accurate enough for most purposes, though you might find it unsatistactory if you ever go for a collet chuck. Happy turning!

George B.

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