Myford ML10 change Wheel question

[Ian George 1Participant @iangeorge1]

I have a Myford ML10. The first gear is fixed via a thread to the mandrel. Is this classed as the 1st driven gear? I ask because I have been trying to find out the change wheel combination to cut a 2.0mm thread on my ML 10. I got confused trying to understand how to calculate what I need and then found a few charts and calculators. However, I get results that suggest Driven 32 25 Driver 63 20 (these are not actual results, just an indication). If the fixed 25 tooth gear is the first driver then I have to have a result that has 25 as a driver.

Sorry if this has been asked before but everything I’ve read so far seems to relate to lathes with a reverse tumbler that drives a “changeable” first driven gear. Would someone please confirm that the fixed gear is the first driven gear and that I should ignore any other combination unless the first driven gear is 25.

Hope this makes sense.

The ML 10 is imperial with an 8tpi lead screw

[Ian George 1Participant @iangeorge1]

this

[BazyleParticipant @bazyle]

The power is coming from the spindle so the gear on it must be a driver.

You can also work backwards knowing the very last gear which is on the leadscrew has to be a driven one.

[BazyleParticipant @bazyle]

2mm is quite an easy one 25, 100, 63, 25 if you have the gears. Gets a bit annoying if you haven't got the right ones. Note that the 63 is always a driver for the metric conversion so is always in that position.

[Clive HartlandParticipant @clivehartland94829]

The driver for metric will be a 25 tooth wheel permanently on the spindle, for 2mm thread it needs a 50 and a 63 on the first stud, then a 45 idler on the second stud to another 50 wheel on the lead screw. this from the book. I doubt it can be any simpler than that.

[Mick B1Participant @mickb1]

Have you looked inside the gear cover? There was a diagram and table there on my Speed 10 IIRC.

[Ian George 1Participant @iangeorge1]

Thank you both very much for your help, I do have the change wheel information supplied by myford and it gives me the detail that you mentioned Clive. I think my journey with this started when I read somewhere that that sequence wasn't the only one available, the reason I looked was that I don't have two 50t change wheels and I wondered if I could use a different combination with what I had. Then I just got completely lost.

Best idea seems to get another 50t or a 100t as suggested by Bazyle.

Thank you both for your help

[BazyleParticipant @bazyle]

Since you mention other combinations here are a list of approximations used to get 1mm pitch from a number of sources. Arranged in order of accuracy. Obviously you don't use an 11 & 13 tooth gear and multiply them up to what you have eg 22/26 and the 1s are just there because the spreadsheet is set up for 6 gears while sometimes 4 is enough.

I think it is interesting that the early Myford conversions using the awkward non standard gears 73/46 is only twice as good as the earlier Drummond approximation using regular gears from the imperial set. This means you probably have the gears to use the bottom Drummond version without the 63 and not having to get another 50.

driver	driven	driver	driven	driver	driven	mm Pitch	Error
13	19	4	7	29	36	1	2.08855E-05	colchester
1	19	64	11	36	35	1	2.73411E-05	Harrison
25	63	25	35	50	45	1	6.29882E-05	baz
25	63	25	63	40	20	1	6.29882E-05	baz
35	60	45	50	30	50	1	0.000125	baz
63	60	30	100	1	1	1	0.000125	drummond
37	47	20	50	1	1	1	0.000212766	logan
46	40	20	73	1	1	1	0.000342466	myford
65	30	20	50	20	55	1	0.000606061	drummond
13	11	30	56	20	40	1	0.005073052	raglan

Edited By Bazyle on 18/08/2018 23:32:52

[Ian George 1Participant @iangeorge1]

Thanks Bazyle, yes I do have that combination. I will try it tomorrow and post back my results.

[Ian George 1Participant @iangeorge1]

Oh yes…….back to the start now, I can't try it out because I'm limited to a 25t first driver wheel. Perhaps I should have paid attention to the myford guide that Mick has mentioned, it does say that "other change wheels may be required" Perhaps it would be better to spend some time understanding the calculations a bit more. What did you mean about using the bottom Drummond set?

[BazyleParticipant @bazyle]

I was referring to my table that shows two rows attributed to Drummond in that they published the combinations at some time in the documentation for their lathes. Suggesting the lower of those However I now see it does not convert to starting with 25.
That fixed first gear is a nuisance. One of the advantages of a tumbler reverse is that it usually end up with a new stating point of an axle running 1:1 ratio with the main spindle that can take an alternative gear to start the chain.

[John OlsenParticipant @johnolsen79199]

This is going to get a little messy….but given that you can't change the first gear, and also don't have a tumbler reverse….Here is an approach that might work.

First, you engage another 25 tooth gear with the one on the main spindle. On the same axle, you put the first gear of the metric train that you want to use. you build up the rest of the train as per normal. That will get the pitch right. However, there is a good chance that it will be left hand instead of right hand. So to correct that you need to put another idler somewhere in the train. This can have any number of teeth.

The main difficulty I can see with this is that you might not have enough room on the quadrant to mount another stage of gearing.

Have you thought of making yourself a tumbler reverse? You could buy the gears, then you only need to make the other bits.

John

[Clive HartlandParticipant @clivehartland94829]

With 50 tooth change wheels going for £10.50 per why not order today. This from our favourite supply site.

The 2 x 50 wheel appears in nearly all the metric thread set ups.

Clive

[Brian WoodParticipant @brianwood45127]

I have to agree with Clive, it seems a very sensible purchase and overcomes the limiting conditions forced by having a fixed 25 t gear as the starting point.

Brian

[Ian George 1Participant @iangeorge1]

Clive, who would our favourite supply site be?

[David Standing 1Participant @davidstanding1]

Posted by Ian George 1 on 19/08/2018 14:20:05:

Clive, who would our favourite supply site be?

I would hazard a guess at eBay

[Howard LewisParticipant @howardlewis46836]

If you seek perfection, try to obtain a 127T. It will be large, being 20DP, and so may not fit in with a ML10 instead of a ML7. (Are the gears on the ML10 keyed, or are they like the ML2 and ML4, pinned?) Doubt if you will get one for anything like the £10.50 for a 50T.

Howard

[Brian WoodParticipant @brianwood45127]

With respect Howard, your suggestion is rather unrealistic. The 127T wheel will be 6.45 inches in diameter and will not fit an ML7 in the change wheel enclosure, let alone the smaller ML10

The cost would be prohibitive too, even if Ian can find one and the gearing posted by Clive Hartland will give him a pitch of 2.00025 mm. I know you said perfection but have to ask how much closer is he likely to want?

Regards

Brian

[Ian George 1Participant @iangeorge1]

Hello All, I have now purchased a 50t and two 21t (because someone somewhere suggested this was the answer). My original journey down this road was because there are a lot of suggestions that you don't need to stick to the recommended list Myford provide inside the change wheel cover, but, I have found out that you do need to stick to it with the ML 10 (without further modification to the lathe) I tried quite few different combination from the list I printed out from a change wheel calculator web site, I tried a few that might have fitted but didn't quite, I even considered making two non keyed bushed that were a loose fit so that I could pop the gears on and off until I found one off the extensive list that fitted. After a few goes at this I realised that someone far more enlightened than myself has done the calculations for the theoretical and physical gear ratios for the ML10, during this process I realised it's far quicker to order the right gears than to mess about reinventing the change wheel.

But thank you all for your help and suggestions, I've no doubt that many would have worked, but with my limited experiance it was far quicker to buy a solution to my problem.

If nothing else I've learnt a lot, although I can't help thinking that I would have done better spending time all this time trying to get my head around the change wheel calculation instead of looking for a quick fix.

Thank you all, what a great helpful lot you all are.

[Brian WoodParticipant @brianwood45127]

Hello Ian,

The calculation is easy enough.

It is the overall ratio of the change wheel gearing, including the fixed 25T gear, multiplied by the lead screw pitch in mm which at 8 TPI is 3.175 mm

Clive Hartford's set up is therefore 25 divided by 50, that product is multiplied by 63 divided by 50 and all multiplied by 3.175 The stages are 25/50 = 0.5 multiplied by 63/50 [1.26] all multiplied by 3.175= 2.00025 mm

I hope that helps

Brian

[Howard LewisParticipant @howardlewis46836]

Brian,

When I had a ML7, I had a 127T gear, but never needed to use it. If I had, on the basis of "Where needs must" I would have run without the cover for the time that it took to do the job. Knowing that the gears were exposed would have made me keep fingers, and anything likely to fall in, out of the way. Can't do that with the BL12-24, (Don't need to anyway, it has a 120/127 compound idler in the train to the Norton box), the interlock microswitch on the cover would kill the relay and leave me literally powerless! Have cut several Metric threads (mostly 1.5mm pitch for ER Collet holders, but need to change the first Driver gear from 40T to 32 or 36 for some of the other metric pitches.

And THAT with a lathe with a 3mm pitch Leadscrew!

Now you can all go back on topic!

Howard

[RobinParticipant @robin]

Posted by Brian Wood on 20/08/2018 19:45:09:

It is the overall ratio of the change wheel gearing, including the fixed 25T gear, multiplied by the lead screw pitch in mm which at 8 TPI is 3.175 mm

Useful post. So I want to cut about an inch of left handed, M30x2 thread for which I have a die nut.

I divide the leadscrew 3.175mm pitch by my required 2mm pitch then multiply by 25 teeth on the head stock and find I need a 39.6875 tooth gear on the lead screw.

Dont' have one of them but I do have a 40t.

3.175mm x 25 / 40 = 1.984375, so over my 12 threads I will be out by 0.1875mm, about 7 thou.

Only tricky bit is I will need 3 idlers to get the bottom gear turning in the same direction as the top for a left hand thread.

That wasn't nearly as hard/expensive as I expected. Well done Brian

Edited By Robin on 28/10/2018 15:12:59

[Brian WoodParticipant @brianwood45127]

Hello Robin,

I agree with your maths and if you are happy to accept an error of 7 thou then go ahead. You say you have a die as well so you could actually get better than you calculate by using the die to finalise the thread having screw cut it to a sufficient depth to get the die onto it.

The solution before also used a 63/50 intermediary to get a much closer match to 2 mm pitch and using that together with your 40 T gear will give you a 2.5 mm thread to close limits [actually 2.5003125 mm]

I don't know what gears you do have available, but the combination 25/40 x 63/60 x 3.175 produces a thread of 2.084 mm pitch. It also I think corrects direction so that you can cut your left hand thread.

Regards

Brian

[Clive HartlandParticipant @clivehartland94829]

The ML10 handbook for a 2 mm pitch thread from an imperial lead screw. offers the following. 2 mm = Driver25. 1st stud. driven 50/driver 63. an idler of 45 on 2nd stud. to a 50 on the lead screw . L/H thread of course needs anotheridler fitted for the lead screw to go the other way.

[RobinParticipant @robin]

Posted by Brian Wood on 28/10/2018 15:54:08:

I don't know what gears you do have available, but the combination 25/40 x 63/60 x 3.175 produces a thread of 2.084 mm pitch. It also I think corrects direction so that you can cut your left hand thread.

That's what I have on the table inside the gear cover. BUT my simple 25:40 does not involve buying a new 63 tooth change wheel and is out by .016 mm which beats their .084 mm

Very odd.

Is there some advantage to erring on the plus side?

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