Hercus chuck problem I think

Am I having problems with my self centering chuck on my Hercus lathe.
I'm very much a novice when it comes to metal machining.
I've suspect for a bit that my three jaw self centering chucks are a bit off centre so today I pulled my dial gauge and had look and play.
First I put it on the spindle http://img.tapatalk.com/d/14/03/29/zyruzusu.jpgturned the lathe by hand and this is has far as it is out http://img.tapatalk.com/d/14/03/29/dajejezu.jpg
Then I did the same with the chuck the piece in the chuck was turned between centres .
So I am pretty confer dent it is square and truehttp://img.tapatalk.com/d/14/03/29/8umaby4e.jpghttp://img.tapatalk.com/d/14/03/29/3e2ajyde.jpg
So questions are have I set up to check the main spindle correctly ?
Have I set up to check the chuck correctly ?
Is this amount of run out I think that's the correct term, ok or not on the chucks ?
Both my three way chucks are showing about the same amount of run out
If the chucks are the problem ?
I also made sure the jaws were clean before clamping down on the bar for testing.
What should or can I do about it ?????
And lastly am I making sense lol is this normal or not ?
And one last question my dial gauge good ok , bad I really have no idea about quality of this sort of stuff ?
Tho I spend a lot time in here reading all the threads pretending I understand lol.

I suggest you do a search on 'chuck runout', to save us typing the same stuff all over again. :)
FWIW, here is the short version:

1. 'Self centering' is a lie, at least for scroll chucks.
2. Buy a 4 jaw independent chuck and learn how to use it. It's a rite of passage.
3. Most likely your chucks can be improved somewhat by careful attention to mounting.

Thanks Bryan
Imm should of mentioned I have a four jaw chuck
So has you say maybe it's time I stopped being shy off the four jaw and get on with it

Quote:

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Originally Posted by Simplicity

http://img.tapatalk.com/d/14/03/29/dajejezu.jpg

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There's paint there on the register surface of the spindle nose just near the tip of the dial gauge - not where you want paint.
Probably best to remove it, ditto for any paint on the vertical face of the spindle nose where the chucks make contact when tightened, as well as any paint in the nose threads. Depending on paint thickness, removal may improve the concentricity of work holding.

Other than that, give the 4-jaw a run as advised.

Cheers,
Bill

Thanks Bill
Will get the paint off
And see how that goes I didn't think the chuck round all the way up to there but it won't take much either to eliminate the paint either and eliminate that possible cause

And just checked I'm wrong the the chuck does run all the way past the paint :-( lol

Quote:

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Originally Posted by Simplicity

Thanks Bill
Will get the paint off
And see how that goes I didn't think the chuck round all the way up to there but it won't take much either to eliminate the paint either and eliminate that possible cause

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The first issue with the paint is that it invalidates the DTI reading for spindle run out because you are adding the uneven paint thickness to the spindle diameter and measuring both. Admittedly, the run out reading result appears to be a fair guess at the paint film thickness, so there may be even less run out than the initial reading suggests.

There definitely is paint in one patch of the thread, and maybe a patch on the register face of the spindle. The chuck backplate and spindle thread are like any nut and bolt, there has to be some clearance between the threads or you cannot move one relative to the other. Looking at some of the cheaper (Chinese) nuts and bolts you find in hardware shops and barns, the nuts are very loose on the bolt and have a lot of lateral movement. Hopefully the thread on the spindle and backplate have been formed with a lot more precision, but they still need some clearance.

The cheapo nuts and bolts work reasonably effectively, provided that you don't strip the thread, once tightened. This is because the underside of the bolt head and the underside of the nut make intimate contact with the material they are sandwiching, and align to those surfaces and eliminate the lateral movement present in the loosely coupled situation. The same happens with the spindle nose thread and backplate, the tread provides the coupling forces to fix the chuck, but the register faces on the spindle and backplate provide the precision alignment you need to make the chuck reasonably accurate. A patch of paint on the register will cock the chuck to one side and throw everything (including the four jaw) out of whack.

Ok I've cleaned all the paint of carefully soften it with turbs first.
Then just rubbed polished it off with some cloth.
Didn't want to scratch it all up
Then did my first test again same results in my view being a novice it's not the spindle.
I'm pretty sure it's the chucks.
They may and I'm speculating here.
That the chucks had a hard life before coming into my hands
The lathe is 9inch Hercus model AR
And was brought by my father in law (ex machinest)
From box hill tafe just before he left there in the 80s I think.
Unfortunately now the father in law is getting quite old
So can't really ask him for help ?

Hi Just a few observations from me , a novice . :roll:

Your 2nd test . The bar your have in the chuck is sitting in the outer edges of the jaws , this isn't an ideal method for testing the runout of that chuck .

How old is that chuck ? Grab the jaws and try to wobble them from side to side , get a feel of the wear in the jaw guides . There should not be ANY sideways movement of the jaws at all .

BTW a half decent 3 jaw chuck should have around a .003" runout .. Mike

- A brand new, good quality brand name 3-jaw chuck of 125mm diameter in the $500 price class has less than 0.025mm runout. But note that this accuracy can very quickly and permanently be destroyed by abusing the chuck, such as overtightening or using a hammer on the workpiece etc.

- A less expensive chuck in the $300 price class has when new typically 0.06 to 0.1mm runout. This too can quickly be degraded substantially if abused. Lowest cost Chinese and India made chucks have been knows to be off as much as 0.5mm from new.


Please download this .pdf file. Go to page 4. Here you see how the 6 (six) runouts that a chuck can have are measured to DIN standard. It is important that everyone measures chuck runouts the same way (eg same distance from the jaws etc) for the results to be truly comparable.
http://www.tos.cz/tospdf/technicke_informace.pdf

This website gives you the same figures in inches, if you do not like using metric measurements:
http://www.jtsmach.com/jtswebshop/Workholding/LC035.asp

Now you have a good idea what to expect from new, or well looked after used chuck.

Your chuck is not new. The scroll may be worn in places. The jaws may not anymore be a tight fit in the chuck body slots. The Jaw's clamping surfaces may have been damaged and worn by clamping onto the irregular hard outside scale of warm rolled steel. Someone may have used a mallet to straighten bar stock clamped in the chuck. Also, the fact that there is paint on the registration flange of your spindle nose, means that the chuck backplate is not a tight fit to the registration flange, and chuck centering depends entirely on the spindle thread. Chucks do not last forever. If you like to use the 3-jaw chuck a lot, and you expect it to repeat reliably to better than 0.1mm, it is maybe time to consider a new chuck. Chris

Ok I'm starting to think
I buy a new expensive 3 jaw
Learn to use my 4 jaw
Find a good second hand 3 jaw
Or just put up with what I have
Thanks for all the great replys
I feel I'm a little bit further a long this road now :-) lol

Quote:

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Originally Posted by Simplicity

Ok I'm starting to think
I buy a new expensive 3 jaw

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Not worth it because the most expensive 3 jaws have runout... Is in inherent to the design.... I use my 3 jaw much more then the 4 jaw..

You just work around it.... I did fit a new $100 chinese chuck to my Hercus though...

If you get a new chuck, you will need a new backplate as well and machine it to size... The backplate is the adapter that screws onto the spindle nose and bolts onto the back of the chuck.

Have a read through this thread..... with some of my experiences there https://www.woodworkforums.com/showth...31#post1427131

I've never really measured the run out on my 3 jaw. I'm thinking it would not impress me! I just work around it, if I need a 50mm finished piece then I start with 52mm! I have never really seen it as a limitation. It is as good as the lathe it is attached to which is all good enough for my use.


Simon

Looking at the picture, the jaws of the chuck appear to be replaceable soft jaws. Can you make an impression on them with a file? If so they could be a part of your problem. Do you have any other chuck jaws with matching numbers to the chuck?
Mm.

As said earlier the length of material you are using to check is a bit short.

A longer piece passing through the chuck to at least reach the rear of your jaws would give a better reading.

As said the jaws may be worn on the outer edge giving a possible false indication.

If after checking again you have a similar result then there may be something wrong with the jaws or chuck.

Have you removed the jaws from the chuck.

If so have you replaced the jaws into the same position they came from,they should be numbered to correspond with the chuck.

If this is all good, reverse the jaws and do a similar test.

This should indicate if the outside jaw is worn/faulty or if there may be a problem with the chuck.

It's nice to have an accurate 3 jaw chuck, but if all you have is one with runout, it doesn't necessarily matter.
If you can do all the needed machining without removing the job, then you'll have as perfect a result as with a perfect chuck.
Other alternatives to a 4 jaw chuck are to turn between centres - the classic technique. Or, for small diameter work, use a collet system.

I've never seen a small Hercus lathe that uses the so-called register to centre the chuck. There's always been a gap between the mounting plate/chuck body and the cylindrical portion beyond the spindle thread, so it cannot. But if there's enough paint or stuff in the gap, it could muck up alignment. The flat shoulder the chuck butts up against should be pristine.
Just to mention, a common problem is chucks getting stuck by over-tightening. They can be challenging to remove, if they've been allowed to spin up hard into place. They only need to gently come up against the shoulder.

Jordan

Ok as suggested all paint removed from spindle threads cleaned with old tooth brush turps.
Chuck threads cleaned ,no burrs or any thing noticeable .
Did a dial test again with piece of machined brass round in chuck ,but this time as pointed out it was clamped all the way through .
Also noted jaws have been removed prior but always put back in corresponding order ie followed the numbers.
The jaws do have side ways movement when not clamping .
So I suspect it's that the chuck is just worn out it's properly 30 years old .
So I will just have to put up for the time being and as suggested get on with learning to use my four jaw chuck :-)
The other question was the dial gauge.
Is the Kennedy dial gauge any good it was a gift a long time ok in another live I had in the uk
Did a quick google search but could only find information relating to buying them!

Someone has pointed out that the chuck pictured has soft jaws. That means they can be bored true. They may only be perfectly true at the exact diameter you bore them, but they will probably be pretty close at other diameters. Better than now anyway.

But first you should eliminate mounting problems and make sure the body of the chuck is as centered as possible. If you're happy the threads are good, inspect the surfaces between the chuck and back plate. Gently run a fine stone over them to show up any high spots. See if there is any clearance to allow fine tuning of the position of the chuck on the plate. Put an indicator on the body and with the bolts not tight see if you can true it up at all. Also indicate the face to see if it wobbles. If so you may need to take a cut off the back plate.

Once all that is as good as it can be you can think about boring the jaws. Something needs to be clamped in them so they are loaded the same way as when you're clamping a workpiece, but allowing access to the jaws. I'll help you when you get to that point.

Ok some more stuff to check out.
Will do that next time I'm back at the lathe.
My shed is an hour and half way so I only get to play on the weekends at the moment back in Melbourne now
Work live style thing long story :-)
The other thing Bryan you mention is to check the body of chuck with the bolts not tight are you referring to the bolts on the back of the chuck I'm a bit confused there :-)
Thanks everyone for help so far
That's what I love about this forum
Matt

Sometimes the bolts are on the back, sometimes the front. Wherever they are, remove them AFTER making marks on both parts so you can reassemble the chuck and back plate in the same orientation. There may already be some punch marks or similar. If not I would suggest something non-permanent for now.

Once you have the plate cleaned and deburred mount it on the spindle and clock both the face and the rim.

Ok will do
when you mean mark I think you mean what I call a witness mark a triangle for instance in felt tip marker

I just realised they're not soft jaws but hard jaws. I saw 2 piece jaws and my brain jumped a tooth. Sorry about that. :- I'm still recovering from a heavy dose of morphine so that will do for an excuse, although I'm perfectly capable of being stupid all by myself.

So you can't bore them easily. I've heard of hard jaws being bored with carbide but it's outside my experience. Anyway it's good news you could fit soft jaws later. And I think everything else I said is still valid.

Seriously, type 'chuck' into the search box and start self-educating. Every newbie has been down this road.

Am on the road off chuck discovery
Next time I'm up at the house will have another look and play
Mean while I will do some more you you tube clips and some more googling lol
I had never heard of saw soft jaws before but that does make sense of being able to true them up by boring them out
But I think that would be a bit down the road for me

Try this:

Will do thanks Bryan
Matt

How are you getting on Matt? I hope I didn't sound dismissive in suggesting some reading. But with some background knowledge you can ask better questions and get better answers.

A clean out might be the best starting point. Chucks do get full of chips and crud and should be dismantled occasionally.

Thanks Bryan, you just reminded me that one is overdue for a clean out.
One more disc brake to machine for a bloke at work and I'll strip it down.

Phil

Hi Bryan
No you were not dismissive you were just giving me a little slap for being lazy lol.
Haven't had much time.
But I did take the back plate off installed that nearly zero run out.
But now I do notice the jaws have a bit of side play you feel with fingers.
There was a little swaf in the chuck but not a lot that's been cleaned out
The chuck has been put together and still the same problem ??

Is the error repeatable? Is the amount of runout consistent? Does it happen at the same o'clock every time? Is it the same at different diameters?

The more repeatable it is the better your chances of fixing it.

I just tried to repair my old 3 jaw, but it's too worn out to be of much use . If you remove the jaws, take a look at where the scroll in the chuck body engages the teeth on the rear of the jaws .... looking at the teeth from each side of the jaw you will see gaps between the teeth , in my case I noticed that the gaps were even on one side of each jaw but badly worn and uneven on the other side .......... hope that helps Mike

Ok more things to check I may be there this weekend and will have a look
I'm learning heaps
Thanks for all the help so far much appreciate
Matt

Ok did has was suggested still the same and still happing at the same clock position I think
I think the jaws could be the problem but not sure
Has i don't have new chuck to compare to eitherhttp://img.tapatalk.com/d/14/04/12/6ysa3aga.jpghttp://img.tapatalk.com/d/14/04/12/yde9abyv.jpghttp://img.tapatalk.com/d/14/04/12/utanyzut.jpghttp://img.tapatalk.com/d/14/04/12/6adyseda.jpghttp://img.tapatalk.com/d/14/04/12/y9uvy4uq.jpg

That is same jaw in all the pics

Simplicity I admire you perserverence with this endeavour , Have you tried undoing the removable jaws from the main jaws and reversing them,as if you wanted to hold a large flange or such. I am not familiar with this machine ,but the reversing will still allow you to chuck up your test piece ,albeit on a shorter section of jaws , I assume the jaws are held together on the locater step by one or 2 cap head bolts. Before you start try and see which jaw is the culprit,and after reversing see if its the same one or its improved :). In use three jaw chucks can get a strained and even bell mouthed ( slightly wider at the tailstock end of the jaws) this can happen from holding short sections of work at the end of the jaws ,the pure mechanical forces of tightening on the front section of the jaws can eventually take the jaws out of parallel , not easily seen to be sure , it just means at times you have a fuller grip on a workpiece it can be out of true . I recently upgraded my baby sieg C3 to a 4" 3 jaw chuck,of course it was out a bit , so I simply set up a dremel with a suitably mounted stone in my tool post and ground the jaws true , its as good as gold now , at least for my purposes hehe, Doesn't hurt to master the 4 jaw if you have one though :) cheers ~ John