4 jawed chuck - centering

[Stiggy]

I have just got an old Sealey 300 swing lathe and I wonder how you guys centre work in a chuck with 4 jaws - is there a trick to getting work perfectly centre?

I've just spent out on a couple of crown chisels and can't afford a new chuck right now - can someone help me please?

 

[bobham]

It sounds like you have got a metal worker's 4 jaw independent chuck rather that a woodworking 4 jaw scroll chuck. A scroll chuck's jaws all move at the same time and it is self centering. The independent chuck's jaws are moved individually and getting centered is a much more complex procedure. The jaws on chucks that are intended for metal working also have quite small contact areas where they hold the workpiece. That is fine for holding metal but they tend to crush and dent wood. They really are not suitable for turning wood at all.

Take care
Bob

 

[CHJ]

http://www.littlemachineshop.com/Refere ... wChuck.pdf

 

[woodpig]

Not enough information to give a proper answer but I can't imagine anyone would put an engineering chuck on a wood turning Lathe, most of them wouldn't fit anyway. Both of my 4 jaw Independent chucks bolt onto a backplate.

 

[MusicMan]

It's not that hard to do, and +1 for CHJ's reference. You preferably need a dial gauge but for woodwork you can get away with a pointer on a stand; you'll have to estimate the mid points so it will take three or four iterations rather than one or two but is possible.

A four jaw chuck is fine for wood if the jaws are not too skinny. Most woodwind instrument makers turn their products on engineering lathes with three or six jaw self-cantering chucks or a 4-jaw independent chuck. It is normally worth allowing plenty of sacrificial material to be gripped in the chuck, which makes it usually OK for spindle work but very wasteful for bowl turning.

For economy, you could get either a screw chuck or a faceplate which fit in the 4-jaw, and off you go; only need to centre it once. A pic of your chuck and lathe would help to advise you how to do this cheaply.

Keith

 

[Stiggy]

Thanks for the reply guys, it's great people are willing to help!

I found a picture of my chuck online which will have to do until I can work out how to post photos.

http://www.sealey.co.uk/PLPageBuilder.a ... uctid=8079

I had a look on the Axeminster site and found this one - what are your collective thoughts on it?

http://www.axminster.co.uk/key-operated ... -chuck-set

I don't have a lot of money as I've just bought a Crown 9mm Bought gouge, a 6mm spindle chisel and Keith Rowley's Foundation in Woodturning book!

 

[CHJ]

As others have said, that Sealy chuck is not ideal for wood turning, it has its uses if you are an experienced turner but for everyday turning it could be down right dangerous to use without tailstock support of the piece.

The reason being is that wood is readily compressible and to hold an item securely and in worst case retain it should the wood compress and slacken the hold you need jaws that have dovetail form or enhanced gripper capability so that the piece does not fly off at speed if you have a tool catch.

The axminster chuck you have linked to is very small in diameter (63mm diameter) and most suitable for small parts and fine work.

Ensure any chuck you purchase has a thread or an adapter facility to match the lathe spindle.

 

[Stiggy]

I think I'll retire the chuck to the shelf until i can afford a new one.

In Rowley's book he uses a technique of cutting a decent base to the bowl and then wedging that into another piece of wood on a face plate - how reliable is that?

I'm quite happy practicing my cuts between centers and I'm in no rush to produce bowls or anything else - it's just great being out in my shed using the lathe!

 

[CHJ]

..In Rowley's book he uses a technique of cutting a decent base to the bowl and then wedging that into another piece of wood on a face plate - how reliable is that?..

For an experienced turner capable of assessing the security and loads applied by tool presentation it's an OK procedure but personally I would advise caution for someone new to turning without someone more experienced running through the various scenarios with them.

 

[woodpig]

Save up and get something like this once you know what your spindle thread is.

http://www.axminster.co.uk/axminster-cl ... ning-chuck

Edit: Looking at the Sealey site all the current range of wood Lathes have 3/4" x 16 thread which is common enough. Best check yours to be sure though before ordering anything.

This looks only slightly more useful than a chocolate teapot. :?

http://www.sealey.co.uk/popupimage.htm? ... CC5.V2.png

 

[Stiggy]

Well, I took your advice and hopefully Santa will be bringing my new SK100 chuck with C type jaws on Friday!

WOOHOO!