Run-out on face of 4-jaw

This is an 8" camlock fitting chuck. I decided to try and square up an ally bar on the lathe rather than mill (no mill powerfeed) for a better finish and was unhappy with the accuarcy of sizing so checked the runout of the chuck face to find 0.04mm difference.

It was late and i have yet to recheck all three camlock positions, clean up, test and reattach to the backplate in different positions etc but just wondering what sort of 'average' one is likely to expect. (when i tested my facepate prior to skimming it a couple of weeks ago there was hardly any detectable runout at that time).

About 0.01mm on the front face of my nearly 40 year old Emco 150mm 4-jaw, slightly more on the ground faces of the jaws.

Thor

Edited By Thor on 04/10/2015 11:17:12

I would have thought that if the chuck is mounted on a back plate it's more likely to be that than the actual chuck. By backplate I don't mean the fitting on the lathe - any plate actually attached to the chuck itself.

It might pay to chuck something, face and centre drill it and engage a running centre fairly forcibly and see if the run out changes just to rule out other possible causes.

Personally I don't remachine face plates. If made correctly they will be pretty flat were as a lathe will generally face concave by some amount that can vary a lot in some cases.

John

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Just clocked by 160mm Bison which was second hand and I machined a backplate for it to fit my Warco. showing a bit less than 0.0005" so about 0.01mm in new money.

Camlock chucks like any other need to have the mating surfaces carefully cleaned before fitting. After cleaning always wipe with your hand / fingers which are extremely sensitive to any particles that may have been missed by a rag.

If you still have problems, fit the chuck and shine a light from the back to check that the chuck is being pulled hard on to the register.

I have had more trouble with camlock fittings than with any other type (my bad luck I suspect), though once correctly fitted I find them very convenient. I had 2 denford easiturns that both had D 1-3 fittings but the two chucks were not accurately interchangeable.

I have found it useful in the past to remove the pins and offer the chuck up to see if it rocks on the taper although this isn't easy on big chucks.

As others have said the backplate is a key area as well but my past history would suspect the camlock.

I hope you get it sorted and look forward to finding out what is causing the problem.

Regards.

David.

David,

You can say that again about large chucks, one of my 4 jaw independents weighs in at 25Kg, its bad enough lifting it on without trying to find out if it wobbles!

I've no idea what an 8"'ish chuck weighs but it got heavy enough after messing about trying it in every hole option and the same hole several times...

Removed the back plate and been playing with that seperately for a while now. Best I get is 0.02mm runout, typically 0.03mm runout and ocassionally 0.06mm runout depending on which hole and also soem variation between putting it back in and out of the same configuration.

After a coffee break I'll mark the high/low points and see if they remain consistent through all those options then I guess a skim is in order and mark the nose and backpate with witness marks for consistency...? At least the outside of the register runs perfectly and there's a couple of mm spare depth so only the outer part of the backplate will need refacing by, say, 0.05mm?

I have mixed feelings about oil and chuck fittings as it can increase the force they retain at rather a lot. If your getting mixed readings it might be worth putting some slideway oil on the pins. It's a heavy chuck and you might not be applying enough force to pull the chuck really home. Oil will help with that.

When I was working on lathes with big chucks they always had a wooden block that fitted on the bed and also aligned the chuck effectively taking it's weight so all the locking mechanism had to do was pull the chuck in. I've been thinking along those lines of late as I have just bought a monstrous 200mm chuck. The increase in weight over the 125mm grip true normally fitted is pretty dramatic.

John

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The pins were oiled anyway with the same general oil as the gears and oiling points oil recommended by Chester and I always give an oily rag wipe on the surfaces as corrosion prevention.

Post coffee break the highs and lows are consistent and about 1/3rd circumference apart. I;m currently getting a consistent 0.03mm runout on the backplate.. which mayalso be due to the fact that this chuck has been on and off here more times today by many times than in the 9mths I've had the lathe.

I also do use a lathe board..but more to protect the ways than to align the chuck.. it still needs an inch of lift to seat the pins. If going to build one to sit dead in line then it'd probbaly need roller bearings to avoid trapped fingers when aligning stuff...

I've decided to skim 0.05mm and see what happens.

This is a 200mm chuck and yes it's heavy enough...

Edited By pgk pgk on 04/10/2015 21:36:47

Have you checked the fit of the taper into the backplate?

One of my 8" chucks had a similar issue, blued up the taper and fitted the backplate, it showed clearly that the taper in the backplate was incorrectly machined and not mating correctly with the D1 nose. a quick re-machine of the backplate (stting up took longer than the machining) and the backplate and subsequently fitted chuck now fit perfectly with negligable runout. Once you do get a good fit/runout, mark the backplate so that it always goes back on in the same location even with 4 jaw chucks this is important.

It looks to me like it's the backplate not fitting the camlock nose. To get an idea of this, label the tightening socets 1,2 & 3, set a dial gauge upon the face of the backplate slacken the backplate so it is loose (but won;t come off) then tighten up in sequence and note the reading. Slacken the cams until you can just free the plate and without turning the spindle tighten 2 3 1 and note the reading do the same but in order 3 1 2 and note the reading. If there is a difference it will indicate that the taper in the backplate is too small and that the backplate is being pulled into whichever cam is tightened first. Try the trick of removing the pins and seeing if you can feel it rocking, which is probably doable with the chuck separated from the backplate.

If this is the case it is worth checking all the chucks and the faceplate to make sure they are OK.

Good luck.

David.

I'm now totally confused and need to sleep on it.

I skimmed the 0.05mm ad had the backplate running deadnuts true - as you'ld expect. To avoid confusion (I thought) after cleaning everything up I re-attached the chuck to the backplate with the backplate still on the lathe. And got a runout of 0.30mm (WTF)!. Removed chuck and backplate.. checked and cleaned everything again, seperated chuck and plate.. put it back on 180 degs from before and still have a 0.30mm runout on the face.

Only thing I didn't do is mark the high/low point first time. Currently they are at least 180 degs apart.

the only immediate thought i have is that the 'junction'/'corner' of the register and surface of backplate might not be right although i did feed the skim in until I saw the first flakes come off the register and the chuck body has plenty of relief there. The finish is superb too with no toolmarks at all.

Time to leave it alone today

When I bought my lathe, I discovered that the 8" D1-4 camlock chuck could not be trued up. It turned out to be that the register on the chuck was a bit too big for the female register on the lathe's spindle. A replacement from the supplier (Hare and Forbes) was the same. In the end they gave me their own 4 jaw off their own workshop lathe, after I was able to prove conclusively the problem with dial indicator, with my chuck, and chucks from their stock, (bad) and their chuck (good).

My shed time depends on available energy end of day and farm chores/weather..

The register between backplate and chuck is tight, To seperate I have to tap a thin ally knife edge wedge around the junction.

Having slept on the problem I;m going to try the next two things.. first remount the backplate on lathe a few times to check that post skimming it contiunes to run true. I have stamped a witness mark for consistent orientation.

Secondly time to blue up the register and see if that gives a clue. It's about the only place where there could be a tiny burr preventing it seating.

One of the things that I have never seen documented is how this (Camlock) type mandrel system actually works.

I have only recently changed to a lathe with a D1-3 fitting and its a breath of fresh air compared to the screwed mandrel/chuck fitting.

My understanding of how it works is that the short taper section centralises the two parts as the flat faces are brought into (full) contact with each other.

If the two faces did not come into contact and the parallelism of them relied on the three (or however many) pins and cams being equally tightened, then it would not be a very repeatable system.

Last week, purely out of curiosity I mounted and remounted a faceplate on the lathe and checked its runout about 10 times. The faceplate is one I cobbled together by fastening an ali plate to the lathe's driver plate (which I would never otherwise use). The aluminium has an assortment of random holes that I drill and tap to suit whatever I want to mount.

After machining the edge an face I used a 2 micro resolution finger indicator to check the run-out. Basically any meaningful measurement is masked by the needle movement caused by surface roughness. I could not see any real difference regardless of which pin went in which hole. All my lathe mandrel fittings have a reference mark (which I adhere to) but in reality it does not seem to be that critical.

Ian P

Edited By Ian Phillips on 05/10/2015 11:13:51

Due to miserable weather i got shed time this am (every raincloud....).

This mornings messing about. remounting the backplate alone and it's conistently showing no appreciable runout apart from less than 0.005mm with direction changes/play in the lathe head itself.

Swapping the chucks 'high' side rotated 180 degs to the backplate and with the register blued I got 0.06mm runout. The blueing did show a quadrant of the chuck female being tight. I showed that quadrant a very little sandpaper and also spun up and light sand/scotchbrite on the male register of the backplate. Now when i attach the chuck either way around to the backplate I get 0.04mm runout always at the same high/low points. Repeated bueing shows no marking but the register is still tight enough that it takes a gentle tap to seperate.

I'm coming to terms with the view that the original 0.06mm has been improved by facing the backplate's 0.02mm runout away and that the remaining issue is the chuck itself. I have no facilities for grinding that (or the abiity). I'm also starting to get arm ache.. that chuck must weight 18kg and I've been lugging it on and off dozens of times.

Unless there's any other ideas (or a freebie grinding offer <hint> then all I can think at the moment is to take multiple micrometer measures around the rim to try and prove my point and perhaps try to shim between backplate and chuck body.. One thickness of kitchen foil on the outer low quadrant???

Rain now stopped.. so gotta do some work

ideas?

Out of curiosity I've just measured my 8" 4-jaw chuck on a D1-4 camlock. As near as I can tell runout on the front face is less than 0.01mm.

When changing chucks I normally wipe the spindle end and the mating half on the chuck with a paper towel, but I don't worry about which pin goes in which hole. Apart from adjusting some of the pins early on I've never done anything the D1-4 fittings; it just works.

There is a line marked on the lathe spindle by one of the holes. The only chuck that has a similar line is the 3-jaw, but I don't normally bother lining them up. I almost never use the 3-jaw anyway, as the jaws are quite badly worn. The Burnerd collet chuck covers all the basic turning needs, and if the work is bigger than 1.5" diameter, or an awkward shape, I use the 4-jaw independent.

Andrew

If the backplate is now true and you have a consistant high spot on the front chuck you could try a shim between backplate and chuck at its lowest point, would probably need to be half the thickness of the runout as you will be packing nearer the middle.

Over the years I have seen quite a few big 4 Jaw D1 chucks with bruised taper sockets. I think it is essential to provide some support for these heavy chucks when fitting to the hardened lathe spindles so that the chuck is supported & aligned to the spindle. A properly made chuck board to support the chuck at the correct height should do the trick. Chucks of 8" or over are too heavy to manually fit to the lathe spindle without some kind of aid to align & support.

Another few hours at it and still not winning.

I miked around the rim and the depth of the chuck measured as a variation of 0.03mm in keping with the positions I had marked as high and low..so thought it ought to be simple to shim things out with slips of cooking foil...

First attempt and all i seemed to achieve was moving the high point 90 degs. Subsequent attempts obviosult failed or I wouldnlt be writign this... then removed all the shims and got a worse runout than I'd started with!

I feel that shimming might be canting the register and stopping it seating fully but my blue is undisturbed. Why all shims removed and still out.....well i left it for tonight and next session it'll be back to checkng the backplate is still attaching with a zero runout, recleaning everything and starting again.

I'm sorely tempted (but a nervous newbie) to mount the thing on the faceplate somehow and skim the back.. there's enough depth to the female register for thinned down bolt heads if they'd line up with the faceplate slots and if the runout when mounted matched the measured discrepancy.