Myford ML7 mainshaft

[martyn sParticipant @martyns]

[martyn sParticipant @martyns]

Hi I would like some advice please. I have bought a complete 2nd hand head stock for my ML7 as my existing mainshaft bearings are worn. Myford do not have stock. Would it be easier to fit the mainshaft / bearings into my existing headstock or fit the 2nd hand head stock complete? Im not sure if this will create more problems. thanks

[HopperParticipant @hopper]

Much of a muchness really. The old bearings come out, the other bearings go in. But you probably should rescrape the bearings after doing so, to make sure they are correctly aligned in case they seat sligthly differently in the new housing.

So if you wish to avoid that, probably change the whole headstock. But you will then need to check alignment and adjust by scraping and/or shimming the headstock base mounting strip, if required. Also make sure tailstock is the correct height to match the new headstock. If it's not, it will need scraping or shimming to suit.

The original headstock bearings are pretty much endlessly repairable by blueing and scraping. The white metal is about 1/4" thick so plenty of " meat".

Even with your new secondhand headstock, you may well have to remove a few shims from between the bearing caps and headstock to get it back to factory clearance spec.

Presumeably you have tried tightening up the original bearings by removing shims etc? This is the easiest option and does not require realignment (usually).

[martyn sParticipant @martyns]

many thanks Hopper- a lot to think about. Ill try tightening up the original bearings by removing shims. shimming / scraping the 'new' headstock and/or tail stock sounds a little daunting! thanks

[HopperParticipant @hopper]

Yes, scraping is not really a beginner-level task, although it has been done. But removing the shims is quite simple.

You first have to measure how much up and down movement of the spindle there is. Done by grasping about a one-foot long bar in teh chuck and shaking it up and down. A dial indicator bearing on the spindle just behind the chuck will read how much movement there is. Myford specifies 3 to 4 tenths of a thou movement here. So aim at a bit under half a thou with a normal one-thou resolution test gauge.

If there is more, you adjust it by taking off the bearing caps one at a time. Do the chuck end first. It wears more. Under the bearing cap, where the hold-down bolts go through, there is a shim on each side. Sometimes the factory shims are made from a stack of two-thou shims stuck together, so you peel off the appropriate number of layers. Remove the same from both sides. If no layers are present, you can cut new shims from brass shim stock, in a U shape and put them in place. Use stock the correct thickness to reduce the spindle play. Or buy the fancy shim packs from Myford for a suitable fee and peel off the layers. When finished, measure spindle movement again and repeat process if needed.

Repeat the process for the far end bearing and spindle. Dial indicator on the spindle sticking out of the bearing and move spindle up and down with a bar up the centre of the spindle for a bit of leverage.

If the bearings are not disastrously worn, this is usually enough to bring them back to spec. If after doing the above process, there is measurable side-to-side movement of the spindle, the bearings need rescraping, which is a whole 'nuther ballgame.

PS, before taking off a bearing cap, mark it and the adjoining headstock with a centre punch mark so it always goes back on the same way round. Very important!

 

Edited By Hopper on 01/07/2018 12:26:54

[Andrew TinsleyParticipant @andrewtinsley63637]

Hello Hopper,

I am faced with scraping the bearings on a friends ML7. I have managed to get scraping down to a fine art on "the flat", but I am blowed if have the faintest idea of how to scrape journals.

I have several old books on how to do this. But either the guys writing them have not done it in practice or those that have, don't seem to be able to get the message across in an understandable way.

Where would I start to get this skill? I don't want to learn by messing up someone else's bearings! The other thing that truly bothers me is how do you make sure that the axis of the spindle is true? No one seems to mention this rather tricky problem.

Presumably if the wear is large enough, then the vertical height of the tail stock would be out, after scraping, or isn't this going to be significant?

Andrew.

[martyn sParticipant @martyns]

thanks for the detailed method Hopper. much appreciated. ill try shimming and see how it goes. worst case is I ruin some bearings and have to wait 3 months for Myford to get stock. they tell me their new bearings wont need scraping though I am no expert ta!

[Andrew TinsleyParticipant @andrewtinsley63637]

Hello Martyn.

Please note that Myford DO NOT have any white metal bearings for the ML7. What they do have are some type of bronze bearing(?). But these MUST be used with a hardened main shaft which they now supply. You must not use the new type bearings with your current unhardened shaft. The two are incompatible and will cause rapid wear on your shaft.

Regards,

Andrew.

[martyn sParticipant @martyns]

Hi Andrew yes I spoke to Myford last week and they sell the hardened shaft and bronze bearings as a kit for approx £340.00 thanks for info.

[martyn sParticipant @martyns]

Hi well I tried re shimming the worn bearings and it has worked ( i think) .010mm up and down and sideways. Im still getting a little judder when I use a parting tool on steel though. thanks

[Brian WoodParticipant @brianwood45127]

Hello Martyn,

Mount the parting tool upside down, on centre of course, and run the lathe in reverse.I think you will find that gets over the problem of judder.

You should also be able to get a little closer than 0.01 mm [0.004"] with the bearings, the correct clearance should be nearer 0.001" but not to the point that the bearing begins to 'grab' the shaft. When set correctly you should just be able to turn the main spindle by hand gripping the spindle nose.

Until they have bedded in again after your adjustments, keep a careful eye on the bearing temperatures when running. Warm is OK, but ouch with a finger tip is most certainly not

Regards

Brian

Edited for silly emogy

Edited By Brian Wood on 03/07/2018 18:36:02

Edited By Brian Wood on 03/07/2018 18:36:43

[martyn sParticipant @martyns]

thanks for the replies

[SillyOldDufferModerator @sillyoldduffer]

Posted by Brian Wood on 03/07/2018 18:35:00:.

…

You should also be able to get a little closer than 0.01 mm [0.004"] …

Point of order Mr Chairman. 0.01mm is 0.0004", not 4 thou.

I hope I got that right!

Dave

[HopperParticipant @hopper]

SOD, I'd concur with your analysis.

Martyn, .01MM (.0004" ) play on the spindle is perfect. Bit of chatter on parting off is not unusual. As suggested the inverted parting tool is one good step, more often done with a rear toolpost on the Myford to avoid reverse running with a screwed on chuck. Also, lock the carriage and topslide in position so the only movement is on the cross slide.

Andrew, sorry I did not see your post earlier. Neil has a very good article (  ) up his sleeve on scraping Myford bearings and aligning the spindle, to appear in MEW at some point in the future. In a nutshell, you need to use a small, curved three-sided scraper in a sort of spiral motion along the bore, forming cross-hatch patterns on the high spots. There is an art to it, and it is hard to convey, but not that hard to do. Take tiny amounts at a time, basically lightly scratching the whitemetal surface. Aligning the spindle afterwards, if needed, is done by scraping or shimming the headstock where it mounts to the bed. If the spindle ends up a few thou lower than the tailstock, it's no big deal. Does not affect turning parallel very much. If it is too much, the base of the tailstock is scraped to bring it down to match.

Edited By Hopper on 06/07/2018 03:34:03

[Brian WoodParticipant @brianwood45127]

Posted by SillyOldDuffer on 05/07/2018 20:26:21:

Posted by Brian Wood on 03/07/2018 18:35:00:.

…

You should also be able to get a little closer than 0.01 mm [0.004"] …

Point of order Mr Chairman. 0.01mm is 0.0004", not 4 thou.

I hope I got that right!

Dave

Ooops Dave and Hopper, well spotted! I think heat damage to the CPU is taking place, not my usual performance

Brian

 

Edited By Brian Wood on 06/07/2018 09:28:41

[HopperParticipant @hopper]

…I think heat damage to the CPU is taking place, not my usual performance

Brian

Increase the flow of amber cooling fluid. It's what we do here in the tropics.

[Howard LewisParticipant @howardlewis46836]

Regarding mounting a parting tool inverted and running in reverse, presumably in the normal toolpost.

The ML7 has a screw on chuck with no means of retention for reverse running, so you risk unseating the chuck, and possible damage to the job, and the lathe, not to mention yourself!

By all means mount the parting tool inverted, and run in Forward; BUT in a REAR toolpost. You will not risk the chuck coming off, and get a better result.

Howard

[JohnFParticipant @johnf59703]

Martyn, Re parting off, don’t be afraid to “give it some welly” I.e. a constant firm hand feed, what many people do when it judders is go slower and back off the feed — don’t giive it more feed and you may well find it will then cut smoothly. In the case of really worn bearings or other problems, poor tooling, too much overhang etc, this will not work but it’s one operation you need to do with confidence ! Don’t allow the cutter to dwell on the work either.

John

[Brian WoodParticipant @brianwood45127]

Posted by Hopper on 06/07/2018 10:14:41:

…I think heat damage to the CPU is taking place, not my usual performance

Brian

Increase the flow of amber cooling fluid. It's what we do here in the tropics.

Would that be the ubiquitous Amber Nectar that can be tolerated in pretty much any quantity by the suspension on pick-up trucks? It is the bottle of sherry that is so damaging and it is not a cooling drink under these conditions

Brian

[Andrew TinsleyParticipant @andrewtinsley63637]

Hopper thanks for the heads up on scraping in the bearings on the ML7. I did manage to get my own ML7 pretty close, but it was far more good luck than skill. Which is why I was a bit leary at doing someone else's ML7.

I have a brand new set of white metal ML7 bearings which I am keeping up my sleeve in case I really make a mess of the job.

Thanks,

Andrew.

[martyn sParticipant @martyns]

Hi all- thanks for taking the time to reply to my questions re parting off judder. I found the bolts/setscrews that clamp the saddle to the bed were loose. I tightened them up and the saddle locked solid. re shimmed the rubbing strips and it now parts off a treat (from the front) And I have just ordered a rear tool post ! thanks again

[HopperParticipant @hopper]

You're welcome. Happy lathing.

Your adjustments should make general turning work a lot better too.

[Ben FrenchParticipant @benfrench46909]

Hi All,

Similar problem here, my ML7 has too much spindle play up and down, I've run out of shims to remove. I could buy a new spindle and bearing set from Myford for 300 quid which apparently also requires bearing-scraping to work well. I was thinking alternatively, seeing as there's plenty of thickness left in the bearing shells and both they and the spindle are in good condition, could i just skim of a very small depth from the mating surface on the top bearing shell where it meets the bottom bearing shell, so that it once again properly grips the spindle? I guess the bearing cap mating surface might also need the same amount removed. This could be done easily on my milling machine.

It might also be possible to place a very thin shim between the the upper shell and cap, so long as it has an oil passage…..

thanks

[Dave HalfordParticipant @davehalford22513]

Posted by Brian Wood on 06/07/2018 18:01:55:

Posted by Hopper on 06/07/2018 10:14:41:

…I think heat damage to the CPU is taking place, not my usual performance

Brian

Increase the flow of amber cooling fluid. It's what we do here in the tropics.

Would that be the ubiquitous Amber Nectar that can be tolerated in pretty much any quantity by the suspension on pick-up trucks? It is the bottle of sherry that is so damaging and it is not a cooling drink under these conditions

Brian

Brian,

I'm betting thats one advert that didn't air Down Under.

[Ben FrenchParticipant @benfrench46909]

Brian, what?

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