4 jaw chuck size

[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 :)