Myford 10 change wheels

[DellParticipant @dell]

I feel sure that this must have been asked before but I am dammed if I can find anything in the search I have been looking at the change gears on my new to me Myford ML10 today and I googled what’s in a standard set but that wasn’t much help either because I have found three different versions of a standard set.

I have 2X20 all others are singles 25 30 32 35 38 40 45 50 55 60 65 70 75 and I think the one on the spindle is 25 but threaded I think, I don’t know how much I am going to use the but I will use them to get to know how to use them just in case, most of the clocks I repair/ restore are BA or very old so I have to use thread plates, I would also like to be able to cut metric and possibly BA although I have BA taps & dies, have read that 2X 21’s an 80 a 127 although I think that would be way to big but Myford say 11 extras are needed .

I know there are some very learned people on here so if anyone can make things less confusing it would be much appreciated, I can’t see the point of having the lathe and not being able to use it to its full potential if need be.

I have just had to order a retaining funny looking hollow bolt because when I took the cover off where the change wheels go it fell out luckily I hadn’t used it with the change wheels.

Dell

[DellParticipant @dell]

[John HinkleyParticipant @johnhinkley26699]

It appears that you are not using the site search facility on the Home page ( half way down ). I came up with these two to be getting on with:

Myford ML10 change wheel question

and

Change wheels for Myford ML10

I'm neither a Myford owner nor user, so these may not be of any assistance, but might get you started in your quest.

John

[BazyleParticipant @bazyle]

You have all the gears you need for all normal imperial threads using 4 wheels in the train, sometimes as an idler.
38 is used for 19 and 38 tpi which are for plumbers.
BA and metric are a little more difficult. The 32 may help here.
If you can get 6 wheels in the train then you can do adequate metric threads for nuts and bolts.

If you can send me a PM with your email I can send you a spreadsheet for imperial and metric but at the moment I can't find the one for BA.

[DellParticipant @dell]

I did two different searches John and they never showed up although there was some other post but not what I was looking for.

Bazyle

i have sent you a pm.

thanks

Dell

[Mike PooleParticipant @mikepoole82104]

To cut a perfect metric thread you will need to include a 127 tooth gear in the train. It is rather impractical so many trains have been devised that will cut an approximate metric pitch, the approximations are so close that unless you have a high end metrology lab at your disposal then the error can be regarded as immeasurable and for most practical purposes will not be a problem, a 21 tooth gear is often used in the metric gear trains but is usually listed as an extra to the standard set. If cutting metric lead screws for accurate movement of a slide then the error may be exposed but for other less demanding applications there should not be a problem. BA threads have some very awkward metric pitches that people rarely screw cut, the small size is not usually a problem for tap and die work.

Mike

[GeorgineerParticipant @georgineer]

I presume you know that ML10 changewheels are identical to ML7 ones. I have found Duncan Munro's "Myford ML7 gear calculator" program very useful, and have long since abandoned any attempt to calculate changewheel combinations by any other means. It will not only use the standard set, but will also accept your own list and generate combinations for the pitch you need, and a whole host of close approximations. It's worth remembering that practical thread cutting rarely needs to be very precise, and the metric threads made with some of the 'conversion' wheels, such as the 21-tooth, are surprisingly close to the theoretical values. I have a 127-tooth wheel, and have never found a need to use it.

Duncan's program is at http://metal.duncanamps.com/software.php

George

P.S. Mike types faster than I do.  It's gratifying to see that we are in agreement!

Edited By Georgineer on 13/03/2023 18:37:56

[DellParticipant @dell]

Thanks for replies

Mike as I said I will use my BA tap & die set as I do now but it’s nice to know how to if the need arises.

George

yes I did know that the wheels are the same , and 21 tooth change wheels don’t seem to be available even second hand, thanksfor the link to Duncan’s program.

Dell

[Nigel Graham 2Participant @nigelgraham2]

Two Golden Rules:

1) – Do not get trapped into thinking that because your lathe is an ML10 the calculations must be for an ML10.

No: they are for any lathe with the same leadscrew pitch and wheel set.

.

2) – In the absence of a 127T conversion wheel, the substitute tooth-count is a factor of 126 or 128. So –

21 (x6 = 126)

32 (x4 =128)

42 (x3 = 126)

63 (x2 = 126)

.

The table in the ML7's gear-cover gives several metric pitches with none of those 4 tooth-counts.

I calculated a spreadsheet giving a few surprisingly close metric pitches for the EW lathe, with 8TPI screw but more limited wheel menu and maximum 2-step train. Near enough for up to 10 turns cut a little shallow and finished to profile with a die, sufficient for making most studs and similar work.

[BazyleParticipant @bazyle]

One of the traps is thinking that the reason a 63 works is because it is close to half 127 however when it appears in the train it is as a driver not a driven gear as the 127 is.
Note that 63 is just 3×21 so there is a link based on the way they introduce the primes 3 & 7. It's one of those maths things that the more different primes you can get into the mix the better your approximation. If you follow one of the links given earlier you will see a post I made listing the methods some major makers had used – not their use of primes like 11, 13 & 19 getting them a good result.

[Chris CrewParticipant @chriscrew66644]

Dell,

There's a 21T Myford change wheel listed on eBay for £43.20 plus £6 postage, but it's from Home & Workshop so not surprised at the price.

[HopperParticipant @hopper]

Martin Cleeve's inexpensive book Screwcutting in the Lathe includes all the charts for cutting metric threads on an Imperial Myford, using the standard set of gears (20 to 75 in steps of 5, I think, plus the 38), using compound gearing. Accuracy is about one thou in 3 inches up to one thou in 8 inches. IE, more accurate than the lathe's mass produced leadscrew. He includes the BA gear charts too. And no need for oddball and expensive gears.

A very handy book, well worth buying.

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