Chuck

I was watching Abom 79 on Utube and saw this, one way of machining small items on a very large lathe.

Peter.

I've even done that on the Myford, using a Simat chuck, but I did at least use all the jaws on the big one.

Bill

Thats how I did the wheels for my engine to machine the inside of the rims where the park brake rubs. (They are 2 foot diameter). Holding a 3 jaw chuck in a 4 jaw chuck also allows you to easily centre it.

Paul

Could I fit one of them to my Myford s7.

Steve.

So that's how preserved railways keep a wheel lathe in work, when business is slack!

Howard

I've read reports of hard-steel chucks held in hard steel chuck jaws coming loose, so care needed.

Less risky with a CI chuck.

Neil

Similar to Bill, I've used Unimat chucks in both Myford & Boxford lathes; I turned up a flanged mild steel spigot with M14 x 1 thread on it and the setup is excellent for gripping little fiddly things that can't easily be held in bigger chucks.

We always used copper jaw pads to protect the small chuck and help avoid slippage...

Yes I did exactly that, on spec, at Doncaster show a couple of years ago, got it home then realised mine's a Simat, so 14x1.4mm

Yes, I've now made one that fits, the main advantage for me is that the jaws are smaller, so they fit and expand into smaller holes.

Bill

Is there any guarantee that the OD of a chuck is accurately concentric with the jaws?

No. Always double check it. Its usually within a thou or three but no guarantee. 

Edited By Hopper on 17/03/2020 00:55:07

Does it matter if there is a 4 jaw independent chuck involved?[

Good point!

Hard to tell from the first pic. The second looks like a 4-jaw though.

First one looks like a self-centring 3 jaw in an independent 3 jaw.

First one looks like a self-centring 3 jaw in an independent 3 jaw.

The main chuck seems to be an independant 2 jaw to me.

Nigel B.

ndiy ... but I can only see 1 jaw in the large chuck (despite blowing up the image). Certainly can't see a another regular jaw 120 deg from the visible one.

Perhaps it's using fixed preset stops in two slots and using a single jaw to tighten?

Edited By Bandersnatch on 17/03/2020 15:47:01

In the top picture it IS difficult to see but there is another jaw at 90 deg clockwise from the one that's obvious. You can just about make out the lines across the jaw steps if you look closely.Just ba pity it's all the same colour of muck and rust all over with flat frontal lighting.

Nice going, Keith - nothing wrong with your eyesight! If you import the pic into a graphics program and increase the brightness by 50% and the contrast (a bit) it pops right out .... along with suggestions of the other two jaws.

Like this (somewhat over-sharpened):

Edited By Bandersnatch on 17/03/2020 16:15:12