Thread: Chuck jaws not parallel

i take it that you have put the jaws back in there correct position,if what you say is correct that they wont hold bright stock tightly and it wobbles trying to grind the jaws cylindrical should only produce the same results,except you will probably have a solid grip on your bar stock but it should be running eccentric,good luck

I think "pipeclay" is on the right track. To expand.....the jaws on a 3 jaw chuck are numbered and must be installed in their correct position in order i.e. 1,2,3.
I personally wouldn't go grinding the jaws until I was absolutely sure that all other avenues had been investigated.
cheers.
Bill.

the other thing you can try is to close the jaws up with nothing in chuck,if jaws dont meet equally in centre you may have when installing jaws been one turn out on the scroll,if this is the case remove jaws from chuck,rotate scroll when start of scroll comes in to view in pos 1 install jaw repeat for jaws 2 an 3.

just wondering if you had machined anything in the chuck prior to refurbishing

Hi Pipeclay,

I purchsed this lathe 2 weeks ago, and did not use it prior to refurbishing.

By refurbishing, I mean cleaning and re-bluing some of the parts that had rusted, lightly. No serious restoration or dismantling.

Why do you ask?

Ken

just thought if you had used prior that it would confirm a problem with the re-assembly of chuck,did you check that the jaws meet equally in centre of chuck.

Each jaw is in the right slot, and when screwed right in, meet precisely in the centre. Let's get down to re-grinding the jaws, they obviously are not parallel with the centre line. How do I go about it? Reverse the jaws, and grind a lick off the outside, let's have some more comments, please.

Ken

Originally Posted by neksmerj

when the chuck is tightened, the round stock can be wobbled.
To me, this means the gripping faces of the jaws are not parallel with the centre line of the chuck.

CAN THIS BE CORRECTED, AND HOW?
Mr Graham Collins, this is probably right up your alley.

Hey!
I am the welder remember.
If you want it heated up and beat up with a hammer, then I'm your man.
Seriously,you are on the right track in thinking about regrinding the jaw faces, but the Dremel is not the tool to do it. It just does not have the power required.

A grinder would need to attached to the the tool post.I think an air driven die grinder might be feasible. The sucess would depend upon the amount of chuck runout.

Strangely enough my mate who has done this was here today looking at my lathe. It seems three jaw chucks can be suceptable to the jaws being sprung by chucking out of round items in them - ie reinforcing bar.

The toolmakers and fitters here are the guys who can give better detail on this.
Grahame

if you decide to grind the jaws they will have to be held in a fixed position,you cant have any backlass in them,im not familular with that type of lathe,you mentioned that you might turn the jaws and grind from the out side,i take it you must be able to unscrew the jaws to reverse them,once again they must be ridgid,the only problem with your external method is that when you run them the correct way the jaws will be convex,might effect surface area contact, An other thing that you may like to check is for any hair line cracks in your jaws,when under load they may distort and cause your problem,if all else fails try and buy yourself a new set of jaws and keep the old ones for black steel

Hi Grahame,

Nice to hear from you. I thought you were THE Guru of all things, including a mean BBQ.

The jaws in this mini lathe are about as big as your thumb nail. I still reckon the Dremel will do the job, if not, then it's out with the oxy torch and hammer.

My thoughts on this are, reverse the jaws, clamp in a piece of say 12mm aluminium bar, and grind the OD for concentricity, reverse the jaws, and again grind the OD, which will become the ID, and walla, job should be done. If that doesn't work, buy a new chuck.

Any one else?

Regards,

Ken

Pipeclay,

Your comments are most welcome, and taken onboard.

Ken

Gentlemen,
Don,t you guys sleep at night? I can't believe all the activity in the early hours of the morning!
Re the chuck. Are you sure you can just "reverse" the jaws on a 3 jaw chuck? Maybe I'm a dinosaur but the 3 jaw chucks that I am familiar with have 2 sets of jaws. Inside & outside! When you reverse a jaw the "scroll curve" will be running the wrong way. Yes or no?????
Ken, by how much is the odd jaw running out? Seeing that it is a near new unit I guess we can discount the possibility that the scroll is deformed because something "out of round" has been clamped in it. So maybe you have jaws that are not a set?? i.e. Two no.1's etc. Are the jaws numbered? Could even be stamped with the wrong number.
cheers.
Bill

http://mini-lathe.org.uk/true_the_chuck.shtml

looks like exactly what you're thinking of.

A google for "dremel chuck jaws toolpost" give a stack of hits, most of which look very much like this discussion.

Cheers,
Andrew

Hi Neksmerj,

I have done this operation several times over the years, but firstly I will give you the best advice I was ever given pertaining to using a lathe

3 Jaw chucks are for BOYS
4 Jaw chucks are for MEN

If you need to use a 3 jaw then put it in a 4 jaw and adjust it (with a DTI - clock) to run true.

Now for the real task. You will need a REAL grinder (a die grinder) NOT a Dremel. Click this link to see what I mean.

http://www.justtools.com.au/category15_1.htm

If you cannot buy, hire or borrow one of these then buy a brand new set of jaws. Place one of the cylindrical body shaped die grinder in the tool post via the attachment supplied (or home made) or more commonly known as a toolpost grinder. Then you would want to grip a small (in length) piece of new round bar (tool steel preferably) - the diameter must be large enough to allow the grinding /toolbit to enter the inside the jaws thus the jaws should not move as they are in tension while you are grinding the gripping face parallel. You are likely to move the grinder in and out a few times before the jaws are all being ground at the same time. However, dress the grinding bit with a carbarunum stone and do a final pass with that. Given that the back of the jaws are still at the original diameter just grind them back at 45 degrees until the pip has disappeared and you just have the surface left that you ground.

I know it maybe not easy to follow but hopefully you have a better idea of what to do.

Personally I think you should always buy a set of soft jaws that can be machined to within a 0.0002". Ony the outside of the 3 jaws chuck, one of the rebated holes (used to open/close the jaws should have a mark by it this mean that you should in theory use that one when clamping your bar in the chuck.

Btw, I have been told recently that you could also use a large steel ring and grip this on the outside of the jaws which seems feasable and easier to do. So even us in the trade are alway learning new tricks that what I like about it. So really it is up to you which way you go.

Well bugger me I just googled your query and I found a site that has pictures with it.

Here it is

http://www.homemetalshopclub.org/new...04.html#truing

All the best

MH