Ml4 change gears

Have a read of this to see how to add photos.

A good source of info on ML4s might be the Yahoo Group for Myfordlathes.

Charts of change gears for cutting metric threads with 8tpi leadscrew and standard changewheels appear in Martin Cleeve's book Screwcutting in the Lathe, which is quite inexpensive.

The gear on your lathe, or the one in the other thread, may have been changed over the years if it is the removeable type. Not sure if they went to a bigger gear when they went to the larger diameter spindle. It's possible.

Thanks for replies. Book has been ordered!!!

what i was trying to ask was if the tables i found were correct. as they have different information in them. or are they just different ways of reaching the same outcome?

Ah, there's a bit of a trap for young players shown in your pic there. Your lathe has the optional, but very handy, tumbler reverse mechanism. So the gear on the spindle is not the first gear in the train used to set up for screwcutting. Usually, the gear you have marked as 26T would be 25T the same as the spindle gear. That way, it rotates at a 1:1 ratio with the spindle, regardless of the sizes of the two intermediate idler gears. No idea why or how yours is a 26??? Try recounting and see if it is in fact a 25T.

With a 25T on the reversing tumbler, the 20T gear you have shown coupled to it becomes the first gear in your gear train for using those screwcutting charts. You then follow those charts for the first gear (labelled either mandrel or driver on your charts), first stud, second stud and leadscrew gears.

Martyn,

I agree with Hopper, and you can easily check the truth by measuring the diameter of both gears, they should be identical without having to go to the trouble of counting the gear teeth.

ML 4 lathes were all fitted with a 25 tooth gear on the spindle, locked as yours is with a grub screw across the joint and it was matched after the tumbler reverse gears by an identical 25 tooth gear. The stud that is mounted on was extended to fit the first gear in the chain, the so called Mandrel gear.

The reversing gears are both idlers and play no part at all in the calculations

And your earlier thinking on the differing charts is correct, there are often several ways of setting up gear trains that give the same result for the pitch of a screw thread, no one result is better than another.

Regards

Brian

Martyn,

Looking properly at your picture, the only working gears are the 20 as Mandrel and 65 on the leadscrew.

The 45 and 30 are idlers and make no contribution to the calculation, the other two [35 and 25] are being used as collars to take up the space on the studs

So the threading calculation boils down to 20 divided by 65, multiplied by 0.125 [8tpi as a decimal figure] which gives a pitch result of 0.03846-- inches. Expressing that as the reciprocal gives the final result as 26 tpi and if you look at the entry for that pitch on the ML 4 table it is identical

Regards

Brian

My maths / arithmetic is pretty ropey but the OP says the mandrel is 25 tooth so by my reckoning it looks something like this, using all the gears that are in mesh:-

Ratio (Driver/Driven) = 25/20 * 20/26 * 26/45 * 45/30 * 30/65
                             = 1.25 * .7692 * .5777 * 1.5 * .4615
                             = .384615
Multiply by pitch (.125) = .048076 or 20.8 TPI or about 1.25mm pitch

I rounded the ratios a bit as they work out to about 8 decimal places as is usual with gear calculations. Don't know whether this is particularly useful, is the set of gears shown supposed to provide a specific pitch / tpi?

Of course my calculations may be off or I have misunderstood something (probably both)

John

Edit: trying to space it out!

Edited By Journeyman on 08/04/2018 12:25:51

Yep. Get rid of all the idler gears out of your calculation.

IE, back to the 20/65 as per Brian Wood above.

Edited By Hopper on 08/04/2018 12:25:15

Journeyman and Hopper,

I have made the assumption that the 26T gear was in error, if fact I doubt if it could be made to fit on the standard ML4 reversing cluster anyway and mesh happily with the smaller idlers.

Regards

Brian

Yes, but the mandrel is 25 so should be 25/65 which still gives and end result of .048076 or 20.8TPI !

John

Journeyman,

Sorry to have to correct you, the spindle gear, reversing cluster and the erroneous 26T gear are all part of the first stage in the drive down from the spindle and will normally be, in this case, 25/25 to give a ratio of 1, I have corrected the 26 to 25. Note they are all running as idlers however they are meshed..

The first WORKING gear in the change wheel drive is in this case the 20T gear

Regards

Brian

Don't be sorry! I understand now what you have done. Always willing to learn a bit but things take longer to sink in these days Just to put my mind at rest, I did the calculation again using all the gear ratios but using your assumed 25t gear and got the same answer as you. The idler ratios do indeed cancel each other out...

John

Edit: Typo

Edited By Journeyman on 08/04/2018 13:21:58

Hello John,

I'm glad you have proved it for yourself, the only way really.

There is unfortunately a lot of confusion over gearing in general, especially idler gearing and what effect it has; the best way I can explain it is to consider the idlers as the belt linking two pulleys, it then becomes obvious.

Regards

Brian

Thanks Brian, I think most of my confusion arose from the "Mandrel" gear which I erroniously assumed was the "Spindle" gear not something that was in fact half way down the gear train. It's a long time since I used a Myford. I hope my error has not confused the OP, if so my apologies.

John

Hello Martyn,

There are perfectly satisfactory alternatives to the use of 127 tooth gears for conversion to metric pitches. You would struggle to fit one to your size lathe anyway.

One of these is the combo 63/80 which I suspect will be rather large for a Myford ML4, the other is much more suitably sized at 37/47 that has an error value of 1.7 mm in 10 metres of thread.

Without trying to influence you one way or another, the subject of lathe gearing is of particular interest to me and you might find my book published last year helpful. Arc Euro sell it at £12.50 plus postage. Myford series lathes are covered in some depth with all the charts you could wish for but there is much else of general interest as well.

The title is Gearing of Lathes for Screwcutting by Brian Wood ISBN 978-1-78500-250-2

Kind regards

Brian

Edited By Brian Wood on 09/04/2018 15:27:23

Hello again Martyn,

I have just remembered that my book is based on Myford lathes with gearboxes, so the tables I mentioned with such enthusiasm may not be that useful to you. However, the ML7 tables you listed earlier in this thread extend the range of the earlier ML4 tables and they will be useful for you.

Sorry about that, I got a little carried away. The translation gearing of 37/47 for metric conversion is also correct, the gearbox has no influence on that and I would be happy to construct a table for you FOC using that if it would be useful

Regards

Brian