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View Full Version : What makes a good 4-jaw chuck?



serriadh
06-14-2010, 02:05 PM
So, I'm looking to buy myself an independant 4-jaw chuck for my little lathe (8" swing), and (as usual) I'm confronted with a huge price range from 60 at the bottom to six times that at the top.

Unlike scroll chucks where you pay extra for precision scrolls and the like, where does the money go in a 4-jaw? The only thing I can think of is the material the chuck body is made from, but surely there must be more to differentiate a bargain basement nameless import on ebay from something by Bison which costs a good chunk of the value of the lathe.

I'm prepared to make a bit of an investment here, as I don't want to be stuck with something that is going to be an irritation or limitation in the future. On the other hand, I'm not keen to pay a 500% premium just because the chuck's been finish ground by naked Balinese maidens but is otherwise identical.

Advice much appreciated!

serriadh
06-14-2010, 02:50 PM
Hurr, and I see someone asked an almost identical question on this forum last week.

Maybe I should be working harder on my searching skills.

Alistair Hosie
06-14-2010, 04:56 PM
Don't fall into the trap of thinking all 4 jaw chucks are non scroll ,therefore independent. I have 2 four jaw eight inch chucks one scroll and another independent plus others.Alistair

PeteM
06-14-2010, 05:35 PM
As you suggest, a good chuck will be made of better materials and able to handle higher rpms.

In addition, a good 4 jaw chuck will have its guides and jaws manufactured precisely. This along with a rigid construction will assure a parallel and good grip.

gwilson
06-14-2010, 07:44 PM
The jaws and their guide grooves need to fit pretty well so that the jaws don't tilt backwards when you tighten them down,causing the workpiece to be pushed outwards some thousanths of an inch.

Rich Carlstedt
06-14-2010, 09:29 PM
Pratt Burnard

J. R. Williams
06-14-2010, 09:37 PM
What makes a good four jaw chuck?- Money. I have a steel body four jaw chuck that has served me well for the past 25+ years. Buy a quality chuck that is strong and not speed limited for your lathe.

JRW

Littleleroy38
06-15-2010, 12:58 AM
The big dividing line seems to be whether or not the body is made of cast iron or steel. Steel will be significantly more expensive. However, it will allow you to turn at higher rpms. In contrast, a lot of CI chucks are rated well under 2000 rpm. Supposedly, a steel-body chuck will last longer too.

Arthur.Marks
06-15-2010, 01:33 AM
First, a clarification:
What size?

I see you are listed in the UK. Does 8" swing lathe mean you can turn a 16" diameter workpiece or an 8" diameter workpiece?

I apologize if this is a stupid question. I have seen both in British designations.

Ian B
06-15-2010, 04:13 AM
Another couple of desirable features:

1. Having the mounting machined directly into the chuck body, rather than depending on a backplate. More rigid, less overhang, more room between centres.

2. Having tee slots machined into the face (only applies to larger 4 jaw chucks). Useful for bolting clamping bars across awkward workpieces, making it half faceplate, half chuck.

Ian

John Stevenson
06-15-2010, 04:39 AM
Pratt Burnard

Which are now made by TOS except for the 3 jaw Griptru which is still made in the UK.

I like TOS chucks, they fill a need of accuracy and cost.
The cast iron ones are fine, steel is recommended for high speed running but anyone running an 8" 4 jaw wallowing round at 2,500 rpm with some off centre work in it is going to be wearing it whether it's steel or cast iron