Chuck out of true

Here’s a photo of back plate thread...

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The fact that you wre able to do that, apparently without effort [otherwise you would presumably have mentioned it] seems to confirm that the thread is as it should be ... That is one of the reasons why I suggested doing that first.

You have now eliminated the thread from the list of suspects; without modifying it.

I think it's most likely that there is some barely measureable blemish on [or in] the parallel register area of the spindle nose [or the backplate]. Your indicator tests are looking good; but they cannot tell you everything, because the probe is only making point-contact [ish]

It's probably time to start applying some blue, and checking that register very thoroughly.

I hope it goes well

MichaelG.

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The thread looks good from here, and [as per my previous post] is best left untouched.

It may be a trick of the light, but ... I think there is some scuffing on that parallel register, and that's where you need to focus your attention.

MichaelG.

From reading thru the posts, The backplate thread and register appear to be OK but have you checked if the backplate is running true when attached to the spindle ?

If the backplate checks out OK, the problem must be in the chuck and if cleaned and no swarf in the scroll, etc, then the jaws or scroll is worn and the jaws need a re-ground.

Paul.

Grotto said ----Thanks for all the help

John F - Good point about where the indicator stalk is on the head stock. I did it again against the register and there’s no movement in the gauge.

also checked the back plate on the outer edge. Photo shows maximum...

Grotto, re the above and the relevant photo, a runout of 0.005" is far more than it should be -- look for 0.0005" or better ! From what you say about previous owner it has not been the original fitting/making of the backplate so one must assume something has changed.

As has already been said and this also suggests to me there is some damage, dings of embedded swarf in the register or maybe the threads. A finger nail or tip can often detect imperfections not seen by the eye.

Assuming the thread fitted easily when in reverse and if it is still tight when the right way around then clearly that is the first thing to solve. When that is solved re-check face with your clock and look for an improvement.

Unless there is a serious bruise on the register part its unlikely the bore is damaged but look/feel for any swarf or scoring. However your photo suggests this is not the case. The rear face I would stone this with a very fine India stone - make sure it is flat and not worn !! If you don't have that use a parallel or similar with 800 paper-- use very short back and forth strokes to ensure flatness and work around the the boss not just in one direction. This is to remove only any dings -- take care not to remove parent material.

Once the all the above is resolved should there be no further improvement I would consider skimming the face where the chuck locates BUT take care not to alter the diameter of the location register for the chuck body.

Might be good to say where you are located there could be someone close by to offer hands on help ???

Regards John

Truing the face of the backplate is vital, but if the chuck register also runs eccentrically, something must be done about it. The only thing that can be done to the chuck fitting register is to reduce it till it runs true. This is not the end of the world. Most of the chucks I use have had their registers reduced on purpose. this enables the fine tuning of any size work after slackening the fastenings slightly and truing up the chuck with gentle tapping with a copper hammer before tightening up and rechecking.

Very true Old Mart but we have not seen a true concentricity reading for the register yet and with the dial gauge Grotto is using it will be difficult to do this on the narrow register. The face is out by 0.005" and this will throw the chuck out even if the register is zero TIR so my assumption was too correct this first and see the result.

Should the result not be conclusive then as you rightly say the register needs attention thus the chuck can be adjusted manually before final clamping is applied.

It would be advantageous for Grotto to obtain a suitable clock - dial gauge to enable checking of the register TIR.

All of this may be avoided if the reason the chuck has suddenly become tight fitting is resolved ?? Assuming of course it was OK before it became tight !

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Am I alone in thinking that the problem area is visible in Grotto's last photo ?

... I have identified the 'region of interest' in this cropped version:

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MichaelG.

Nay lad, tha c'd well be right. Possibly a raised lip on the lower edge of the darkest gouge about a pitch or two above the thread?

Worth adding that in the first set of pictures there are scuff marks on the spindle register that might correspond. Difficult to know how serious they might be without copping a feel...

Maybe a bruise is the cause but Grotto's original post implies the chuck was OK up to the point it suddenly went wrong. To me that implies an event, something happened to cause the problem.

I wonder how often Grotto has the chuck on and off his lathe? If he's the kind of user who never moves the chuck, then damage inside is surely unlikely? On the other hand frequent chuck changing might explain bruising.

Not infallible, but new faults can often be traced to something that happened recently. What changed last? Bob Stevenson asked if the chuck had been dropped recently, I'd extend his question to cover anything out of the ordinary such as crashing the saddle, work camming out of the jaws, or a dig-in etc. If more than one person uses a machine, remember the one who had the accident may be reluctant to admit it!

In the absence of a crunch, I don't think Grotto has tried stripping the chuck and cleaning the insides yet. Swarf gets into the works and it can effect the jaw settings. That's my number one suspect until swarf is proved innocent. Less likely perhaps the scroll is damaged.

I'd suggest jaws inserted in the wrong order except the error it produces is obvious, hence unlikely in this case.

Before cutting metal to fix a problem I like to be certain of the cause. One thing's for sure; removing metal from the wrong place is likely to add more problems.

Dave

You're right about implying an event. I don't think those marks inside the backplate register could've arisen without one that involved some force beyond simple manual pressure.

Seems as though son might know more about the incident that caused this. Father should be more likely to know the registers need to be scrupulously clean when swapping chucks and would surely have noticed it ‘on his shift’, before posting on here. Ages, experience, etc of dad and son might be revealing?

That the 4 jaw goes on fine indicates that the back plate is damaged (or the 4 jaw back plate is loose on the register).

I think I would know if I had trapped some swarf in the register on my lathe, so it is likely a third party! Aluminium swarf would ‘smear’ quite easily, perhaps, but it would still be there in a thickness sufficient to throw off the accuracy of the chuck.

Show this post to son - and watch for his reaction?

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Like [perhaps] bumping the register on the end of the spindle nose thread whilst removing the chuck ?

No offence to Grotto intended ... it's all-too-easy to do.

MichaelG.

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We're on the same page, Dave.

Thanks again for all the help!

Unfortunately I’m located in Auckland NZ, so guess it’s not so handy for someone to drop around.

I do change chucks every so often, I didn’t appreciate they should be scrupulously clean (should have), and can’t swear it hasn’t been bumped ( hadn’t been dropped). I haven’t had any major crashes, but have had a few dig ins when parting. May have bumped the register?

no offence taken by any suggestions of mistreatment or carelessness, I tend to learn best by making mistakes and am learning to slow down and clean up, but limited time and space makes it hard.

i have pulled the chuck apart, no sign of any swarf in the gears, but will give it a good clean tomorrow (work & family have prevented me from putting in any workshop time today.

JohnF - what type of clock - dial would I need to check register TIR?

I'll investigate the “region of interest” tomorrow.

I’ll avoid removing any metal in the short term, that would be a last resort, can’t see that route leading me anywhere other than getting a replacement.

Judging by how often I make them it's far too easy to make mistakes! A jolly good thing about owning a Chinese lathe is operator error doesn't worry me much. I'd be a nervous wreck if I was learning the ropes on a new Myford Connoisseur and kept dinging it.

If Grotto's chuck problem is due an accident, it's more important to know what it was than to play the blame game.

My mistakes are confessed on the forum because they might help someone else. Or perhaps it's because my cupboards are so packed with skeletons there's no room left for keeping the latest embarrassments secret.

Dave

Grotto, Dave's [SOD] comment is very pertinent :-

Before cutting metal to fix a problem I like to be certain of the cause. One thing's for sure; removing metal from the wrong place is likely to add more problems.

Dave

Also Micheal G and MickB1 have good points, particularly Mick's comment about the spindle scuffs, looking at your photo's I would polish the machine spindle register under power with very fine or worn wet & dry - just enough to remove any surface grime or small burrs, DO NOT remove any scoring or deep marks just polish the surface, probably best with the paper wrapped on a suitable piece of flat metal. Remember to lubricate this area with oil [not grease] when fitting your chucks etc.

The dial indicator type you need is similar to this **LINK** I'm sure you will find a local supply of something similar

John

For checking the Register, you are looking for very small errors, so a Finger Clock, of the Verdict type would be ideal, since they tend to be graduated in 0.0005" or 0.01 mm increments. By estimating between the graduations, you can achieve better than that.

Personally, I would be very wary of removing metal from the register on the mandrel, unless it is a raised bruise or burr. Once certain that the mandrel is free of burrs, if the problem persists, then my attention would be turned to the 3 jaw chuck and the faceplate to look for burrs on the register, or dirt or damage in the threads.

If the worst came to the worst, the chuck could be fitted with a new backplate, and the faceplate worked on until it is a snug fit. Any work held in the 4 jaw, or mounted on the faceplate will need to be centred, so any small errors will be countered by this.

Howard.

There is certainly a mark in the picture, it looks like the backplate was screwed on dry, and I always like just a tiny bit of oil when I change chucks.

The lever type indicators are much easier to use on machinery, I would only use plungers in conjunction with a surface table, with their axis vertical.

The recent legacy of tools and machinery included a Baty or Mercer plunger DTI in a box with a number of accessories including lever type adaptors. I hid it somewhere and haven't had time to have a good look at it. I wonder if such lever converters are available these days? I have just looked on ebay, there is a listing showing the lever I mentioned: 264409293958. The lever style can be bought very cheaply, probably not as robust as my Miyutoyo's, but so much easier to use than a plunger.

Edited By old mart on 31/07/2019 21:41:00

Managed to get some time today, so pulled the chuck apart. No significant swarf, but gave it a good clean and lube and put it back together.

It looks like some swarf has got between the scroll plate & chuck at some stage, but I don’t think this would cause issues.