Myford ML10 countershaft

My ML10 has way too much play in the countershaft. Guess I’m going to have to fix it. (* sigh! *)

Myford no longer sells replacement parts of the countershaft. This shouldn’t be a problem, since Oilite bushings can be sourced elsewhere. Also, the countershaft is not an overly complicated part and should be within my admittedly modest machining capabilities if it comes to that. Nevertheless, I do have some questions…

1) Does anyone already have the dimensions of the ML10 Oilite bushings? Length, outer diameter, inner diameter?

2) The same question goes for the steel countershaft. Does anyone have the measurements of same? Or even (gasp!) measured drawings?

Yes, I know I could disassemble the countershaft and then measure everything, except that this would leave me without a working lathe just when I need it the most... too, I might run into unexpected ‘reassembly’ issues, again, at the worst possible time.

If the steel countershaft is worn and I have to machine a replacement, then…

3) Is there any particular grade of steel required for the countershaft? Or will most anything do?

4) I have experience with TIG welding and thought that another possible approach to repairing the countershaft would be to build up the worn areas with silicon bronze and then turn the shaft back down to the correct OD.

Does anyone have an opinion about such a repair?

Edited By Ignatz on 03/08/2017 11:27:02

With no detailed knowledge, and a Masters Degree in stating the painfully obvious, the shaft dimensions are almost certain to be Imperial.

From memory, the countershaft on my ML7 was 3/4" diameter. The longitudinal dimensions should be measurable from the original, as should any unworn diameter of the shaft.

Possibly the more difficult part of making a new shaft may be cutting the keyways, otherwise should be reasonably doable.

Howard

Would my best approach be to start machining the shaft from 3/4" ground stock?

If so, which grade of ground stock would be the most easily machined?

- also -

Just had a kind reply from the folks at Myford UK. Unfortunately, they do not seem to have any remaining information on the ML10,

Having replaced the Bushes and the badly scored countershaft on my ML7, the original appeared to be Mild Steel when I used it as raw material for something else. So you have choices, Mild Steel, Ground steel or even Silver Steel.

Literally, you pays your money having made your choice!. Obviously, Silver steel will less easily machined than Mild Steel, but will be less likely to wear.

Howard

Bright steel instead of silver steel seems to me perhaps the best economical decision but for only one bit of shafting this may not be so much of issue.

In any case, having the stuff ground to size would save me a lot of machining work, meaning I would only have to cut the grooves, keyways and do a bit of chamfering on the ends.

If as you say the shaft is mild steel then the answer is to use, 'Ground mild steel' available from Reeves or such places.

The shaft sits behind the machine and gets neglected for lubrication. It should be lubed every 4 hours with Shell Vitrea or Esso Nuto or equivilents.

Most lube points say 4 hourly lube. How many follow that?

Clive

Clive, thanks for the pointer about using ground mild steel. Probably good enough for this purpose.

You are doubtless correct about that lubrication neglect. The headstock spindle of my ML10 is running pretty much within tolerances (as far as I can tell), but that countershaft... horrors!

The end of the countershaft with the triple pulley moves visibly when pushed.

Edited By Ignatz on 05/08/2017 11:24:06

Sorry folks, this one is a bit wordy.

I bit the bullet and disassembled the countershaft assembly to inspect for wear and/or damage. I was surprised to find that it does not match the technical drawing in the Myford ML10 manual.

This is obviously an earlier version of the countershaft unit in which no bronze bushings were used. Instead, the cast iron was bored out, with the steel countershaft running within it, somewhat akin to the way the lathe spindle of the ML10 is carried in the cast iron of the headstock. The difference being that the steel of the countershaft is not hardened. Also, the countershaft sports two grooves at the lathe end to help distribute the oil.

The photos of the journals of the casting and the ends of the countershaft show wear as well as an amount of galling. This unit was evidently run dry at some point, much to its detriment.

The wear is not evenly distributed. The journals in the cast iron measure as large as 0.753” at the motor end, and up to 0.755” at the lathe end. The steel of countershaft seems to have taken the bulk of the wear, measuring 0.7233” at the motor end and 0.7235” at the lathe end.

All of this translates into a fair bit of runout – as much as 0.0297” = slightly more than 0.75mm (ouch!). No wonder this joint has been weeping oil.

My assumption is that the steel of the countershaft started life as a true 0.75” and that the journals were bored very slightly larger. Perhaps someone would know what an acceptable beginning tolerance would have been.

Anyway, I’ve still got to fix this somehow.

What would be my best approach?

If I simply repair the shaft to bring it back to a true 0.75” – either by bronze brazing or else a complete re-machine – I will have cut the total runout to something like 0.005” which is already way better than what I’ve got. But this begs the question. Will the galling in the cast iron journals just start nibbling away at my new shaft? I’m thinking that the galling will have been worn down a bit over time, but this is only surmise (or wishful thinking).

I have no machine at my disposal to bore out or hone the cast iron journals… excepting if I tried to sort of use the ML10 as a hand-turned device to do the work with the cast iron countershaft unit somehow clamped to the carriage. Scary!

Another thought was maybe to run a hand reamer through the countershaft journals to clean them up. That would be either an adjustable reamer, or else a carefully-chosen, oversize reamer. Naturally, I would have to slightly oversize the bearing surfaces of my steel countershaft to suit.

What would be my chances of success with this approach?

Until I get this fixed I’m going to slap it back together so that I at least have a working lathe.

Because of the heavy amount of play in the shaft I thought to pack the journals with graphited grease instead of using oil at the moment. Is this a bad idea?

Edited By Ignatz on 06/08/2017 22:30:24

No grease, use an EP 90 oil which is thicker and will stay in the journal. In the long run you may well find that it will be OK to use for some time while you try to find a part on Ebay perhaps and work on that at your leisure, you may even find a newer one with bushes, I would start looking and see what comes up.

Clive

Thanks again, Clive. I'll take that 90-weight oil tip to heart and order some tomorrow.

Have you an opinion about the idea of my laying down silicon bronze onto the shaft and then turning it back down to size?

Ignatz,

The same thing happened to the countershaft on my early ML10 not long after I got it - I forgot to oil the countershaft on a long job. I repaired it by inserting Oilite bushes in the countershaft casting and I must have made a new shaft. When I say I did the work, I actually got the help from colleagues at work who had access to machinery in the mechanical workshop to bore out the casting and mill new keyways in the shaft. It was about forty years ago and I can't remember the exact details and I would probably have to strip down the assembly to see if there were any clues as to exactly what was done. But the new shaft and the Oilite bushes are still working well today. I also apply 32 grade oil regularly so there has been little chance of the bushes drying out.

Jim.

The quick and easy way to repair would be to use a length of 3/4" diameter bright mild steel bar to make a new shaft and run it in the bearings as they are, or maybe after a very light hone or ream to knock any roughness off. Yes there will be a few thou of slack but not enough to stop proceedings.

If you want perfection, hand ream the holes until they are cleaned up and both teh same size, and in alignment, then machine a custom shaft down from a piece of 7/8" or 1" bright mild steel bar to suit the diameter of the bearings, with a one thou clearance for oil. Then fit some small drip oilers (available cheep cheep on the net from China) to keep the lube up to the bearings.

If you want modernization, buy a used part from a later ML10 with the sintered bronze (oilite) bushes and fit new bushes. These hold oil in the porous material and won't need the drip oilers providing you remember to add a few drops of oil every day the lathe is used. Then sell your old part on fleabay to recoup part cost.

Personally I'd go for option one and see how it goes for a while. If not happy, search around for the part for option 3 while still using the option one repaired part.

My path is clear. EP 90-weight oil to keep the countershaft happy and running in the short term.

After that I order some 3/4" ground stock and machine a replacement shaft. This should bring me up to (only) slightly sloppy but workable runout on the countershaft.

When time permits I can the think about possibly reaming the journals and machining a slightly oversize shaft to match.

Jim, the suggestion to bore out the casting and insert Oilite bearings sounds great... except that the ML10 is currently my largest machine tool and otherwise I do not have access to anyone here who could do that sort of work. I'll have to leave that as a future possibility.

I have the later ML10 with oilite bushes, so have little problem there. However, I have recently obtained a 1/2 HP, 940 rpm 3phase motor and inverter, and am wondering whether I need a lay-shaft at all with the speed variation available (5 to 1500 rpm as I have set up the inverter).

Any advice on this, please?