Myford ML2 Change gear headache help needed.

PS, that 15T gear on a small diameter shaft is not actually a 16T that meshes with the leadscrew for the thread chaser/indicator dial is it?

Evening John and Hopper, the plot does indeed thicken as I've just been in the garage for a closer look at the tumbler reverse and it turns out that all the gears currently fitted to the lathe are Mod1. I've taken the little compound gear off the tumbler to compare it to the standard 20dp change gears and the difference is so obvious I'm surprised I hadn't noticed before. Also that grey 50t gear i just bought of a certain Myford seller on eBay looks a bit p1ssed to me lol

I'll go back into the garage and get you that pic of the tumbler reverse set up you asked for.

Here are the photos of the reverse tumblers . I think my quadrant may be different as well as in other photos of peoples ML lathes they have a quadrant with 2 slots arranged in a sort of V where as mine just has the single slot. I don't know if that will matter but there are plenty on ebay if I need the V type.

The black handle selects forward, reverse or not engaged, the red handle just tightens the v belt.

I have an old ML4 which is very similar to that, and I'm sure that your change gears and mounting are very different. Someone has heavily modified your machine, but that is likely to be a good thing. The actual Myford gears were quite good, but the original method of mounting left a lot to be desired.

I don't know if all of your gears are metric or not. There's no reason not to use metric gears if that's what your machine has been converted to use. The main thing of importance is that all the gears you use have the same pitch.

Don't forget that idler gears can be anything. An easy way to think about this is one tooth in, one tooth out. The only way you get a change is to have two gears on one shaft. Then you certainly don't get one tooth in one tooth out.

Your lead screw is probably 8 TPI, but that might have been changed too. If it is 8TPI then the 20T and 50T gears sound right for 20TPI. Just use whatever idlers bridge the gap. It looks like you have a tumbler reverse, so you can have odd or even numbers of idlers, as you find convenient.

Edited By Andy Ash on 25/05/2016 23:18:47

Yes it looks like the old engineer fabricated that reversing tumbler and belt tensioner himself. Judging from the rest of his work, it is quite possibly a better set up than the original ML2 rig.

It looks from a rough count of the gear teeth in your pics that he has a 30T on the mandrel and a 30T gear as the inboard gear on the tumbler output stud. So that gives you a 1:1 ratio. So, yes, you could set up your 20T gear as the outboard gear on the same stud and it would be the same in effect as having a 20T mandrel gear.

Thus you could put your 20T on the reversing output stud, the 50 on the leadscrew with a couple of idlers of whatever sizes fit to connect the two together in a train. Dont use any compound gearing in the idler train. Just gear to gear to gear etc.

I reckon if your old lathe could talk it could tell some stories. Quite the innovator that previous owner by the looks. It would be fascinating to know what models etc he made on the old machine over the years.

Thanks Andy and Hopper. I was told the original owner used it to build model jet engines, The table he built for it weighs a bloody ton I can tell you that...I had to take the legs off it so I could move the table top. I think the compound on the tumbler is one piece so i may be buggered unless I can find more Mod1 gears but being new to lathes I have no idea what they would be fitted to as standard or where to look for them. According to the PDF version of the user manual, which assumes the reader has a good knowledge of lathes already, any of the change gears will fit on the mandrel but I'm sure the mandrel is a bigger diameter than my 20dp change gears but I'll check to be sure. If I can swap out the Mod1 gears and forget the tumbler reverse and go direct from mandrel to lead screw via idlers all using the 20dp change gears that'll allow me to cut threads. Then I'll put the Mod1 gears back on so I can use the tumbler reverse and also benefit from the very slow feed rate...does that sound feasible?

In the mean time I'll try and find out where I can get hold of more Mod1 gears so I an build up a selection so I don't have the mammoth swap out each time I have a thread to cut.

If I understand things write The full diameter of a Mod 1 gear is teeth+2 in mm? if that's correct then are these what i need? **LINK**

I dont see where it says what the mini lathe gears' module number is, but if you contact Ketan at ArcEurotrade i am sure he can quote you chapter and verse on that stuff.

I would still try to figure out how to use the 20dp gears that you have. Is the gear on the main spindle 20dp? if so, and the last gear in the tumbler group is the same number of teeth, you have a 1:1 ratio, and may be able to mesh a 20dp gear with the inner gear of the compound pair and carry on in 20dp from there.

Or, you may have to make up a compound gear to go on that tumbler output stud with a gear that matches the main mandrel gear compounded with a 20 tooth 20dp gear. Your list of extra gears, I understand, includes a 30T and a 20T so if you mount these on a stud, pinned together and use them to replace the current compound tumbler output pair, you should be able to cut your thread with the 50T on the leadscrew and couple of idlers in between.

The more I look at that tumbler combined belt tensioner, the more intriguing it gets. It looks quite possible that the old engineer had the belt tension handle right there next to the reverse tumbler so the belt tensioner could be used as a clutch to disengage drive before shifting the tumbler from forward feed direction to reverse, then re-engage the belt. Much quicker than stopping the motor, changing tumbler and restarting etc.

And if your 20t 20dp will not fit over the diameter of the main spindle, your lathe may have been fitted with a larger than standard spindle, with larger bearings and a larger hole down the middle. All very advantageous.

Jet engines eh? A look into the making of jet engines may reveal more about what goes on that rather special vertical slide. Machining turbine blades is rather specialized and maybe this was the gizmo used.

Edited By Hopper on 27/05/2016 09:58:58

Edited By Hopper on 27/05/2016 09:59:59

The tumbler compound gear won't be one piece as it would be difficult to make like that. The teeth on the smaller gear can't (easily) be cut right up next to the bigger gear. It is probable that the smaller gear has a section of plain shaft onto which the larger gear is pressed or glued or pinned. Heating up the pair will break the glue down and release a press fit if you can arrange to press it out with a vise. Don't worry about the heat harming the gear as they are low stress in this application and do not need to be super hard.

The vertical slide thingy is not special for making jet engines, just an adaption of a random bit of bigger machine that the original maker happened across, like the gears, in some scrapyard or at work.

"I think my quadrant may be different as well as in other photos of peoples ML lathes they have a quadrant with 2 slots arranged in a sort of V where as mine just has the single slot. I don't know if that will matter but there are plenty on ebay if I need the V type."

Richard, it doesn't matter. Earlier ML1-2-3-4s had a single slot quadrant, later ones had the vee shaped two slot ones. As far as I know, the only practical difference is that the vee style is easier to set up.

The pins which Myford used to link the gears were silver steel, 3/32" diameter and 1/2" long. The originals had nice domed ends.

George

I don't think it makes a difference but I noticed something else about that machine.

There is a square boss on the back of the headstock casting. On mine the boss has a spot face and a tapped hole. The hole takes a threaded pin and is the pivot for the tumbler assembly. Given that the hole is not there, then the machine must never have had a tumbler originally.

I also wanted to qualify something I said earlier.

"The main thing of importance is that all the gears you use have the same pitch."

With hindsight this should have read;

"The main thing of importance is that all the gears you use have the same pitch, where they mesh".

Hopefully it was obvious that you can mix gear pitches in a gear train. Where the gears mesh the pitch must match or the teeth will interfere, crash and bind.

Having found my copy of Ivan Law's book I did some perusing last night. BTW it is published by Argus Books under their Workshop Practice Series and is a very good book to have to hand.

MOD = 25.4/DP and DP = 25.4/M

So a 25T gear with MOD1 has a pitch circle diameter of a fraction under 1-inch. That is a little finer than a 20DP gear which allows more teeth than a 20DP on the same size gear. Doubling the DP reduces the gear diameter to half for the same number of teeth. A 20DP gear with 25T would be MOD 1.27, a 20DP gear with 50T would be MOD 2.54 etc.

My guess is the modifier of the lathe worked for a company that only had MOD gear cutters and so it made sense to use them rather than the older DP cutters. Anyway, what you have looks perfectly OK and is probably better than the original Grayson/Myford setup.