4 jaw chuck size

[reefy86]

when buying a 4 jaw chuck such as a 200mm chuck is that 200mm of material size or the chuck size its self?

[Neale]

Diameter of chuck body. Typically it will be able to handle work larger than its own diameter but that depends on the work and the lathe/spindle.

[reefy86]

looking at the data sheets its a little confusing because according to this for a 400mm work area which is what i am after it looks as if i need a 500mm diameter to use up to 400mm cutting material but looking at the cad model i can scroll the jaws past the body diameter so i would of thought that a 400mm chuck can handle 400mm material.

Look at D5

[Doddy]

I'm voting with the OD of the chuck. Re. 400/500 argument - maybe the chuck cannot reliably hold the larger workpiece on the last threads of the scroll (ok, indie 4 jaw - the chuck screw), hence the manufacturer's stated limitation?

Although you are able to wind the jaws proud of the chuck body - be warned - it's a good way to lose a knuckle or two (not that a lathe doesn't present any number of ways to lose knuckles and ring fingers already)

[Neale]

You can certainly wind the jaws outside the body diameter and hold work at least the same diameter as the body. However, if you are looking at typical lathe chucks, do you realise how heavy these things are? I have 200mm 4-jaw chucks for my lathe (metal-working) and it ideally needs two hands to comfortably lift and fit it. Up to 300mm and you are getting to the point of needing a hoist to move it.

[reefy86]

Its more for indexed rotation and yeah i realise they are going to be heavy but thats what i go to the gym for :)