Myford ML10 change Wheel question

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

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

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.

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?

Robin,

The 63 gear brings the translation to metric closer to the ideal of 127 teeth and your use of the 40 tooth gear is purely fortuitous in the answer it gives.

As you saw before, the 25/50 x 63/50 x leadscrew pitch gives a very close result for 2 mm pitch. Working with a very limited selection of change wheels will make things very limited for you

It is all of course your choice

Brian

I am not sure about that, but I am not here to argue

I left it unattended on a slow feed once. The saddle pushed the headstock back until it snapped the bottom of the gear quadrant off and graunched the lead screw under the split nut. Seeing as how both results would stop the saddle I think it is most unfair that I had to suffer both. Anyway, since then I leave a slow feed gear set up and avoid thread cutting. Too much regret when I have to hold the pieces together whild locking the quadrant.

Perhaps I exaggerate, if I really cared I would drill and screw the quadrant it back together

Robin,

I'm sorry to hear of that disaster, I am surprised at your candour.

At my last place of work I saw the result of a few moments of inattention on a power fed drilling job through a stack of blanks.

The drill grabbed on break though and was forced through the jaws of the chuck where it continued on to burn through the soft back of the chuck into the hard Jacob taper arbour. Fortunately we saw the smoke and stopped the operation before serious damage could take place.

The drill was reduced in length by about 1.5 inches and the shank was by now at half diameter. Despite that, we were able to recover both the chuck and arbour and with a new drill carry on with the job

Your quadrant could be recovered by careful brazing of the broken pieces, it would be stronger than trying to fix it with small screws. 

Brian

Edited By Brian Wood on 31/10/2018 18:19:25

We are not going to agree on anything, but I still like the way you think

Robin