Thread: Hercus chuck problem I think

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