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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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.

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.

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).

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

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

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.

I don't know if it will help, but the clearest intructions I have seen for Camlock fitting are on page 2 of this.

In my limited experience; the less than 0.004" starting-point is crucial.

MichaelG.

I had a similar problem with a couple of D1-5 Camlok baclplates before, It turned out that the taper in the backplate was "out ". The taper was correct but not of the correct dia [ too small ] so I set everything them up on the face plate and got the correct angle for the taper and had to take off 0.09 mm They were both the same so at least the error was consistent !! They now locate perfectly on the spindle nose. The tight taper was causing them to rock on the spindle nose, and you could tighten any one of the 6 camloks and that would cause the chuck face to deviate away from the spindle axis because it was not getting pulled fully up to the face of the spindle, with the result that any bar would not be held straight. I now only ever use Rohm ones, and no more having to machine the tapers. The Camlok system is great, but the tapers MUST be spot on or all bets are off.