The 200 mm chuck will be a lot heavier to lift and fit, if that is an issue for you. I have one but on a 12" swing lathe and have to be careful not to drive the cross slide into the extended jaws. I suggest 160 mm for yours.

I suggest you look out for the original Pratt and Bernard 4 jaw that was fitted to the Boxford. You should be able to easily pick one up complete with (or was it integral to?) the backplate from the regular second hand tool suppliers.

It will probably be a 6" and will cost a fraction of a modern chuck and be many times the quality.

I think I paid £50 for one from one of the dearer second hand suppliers two years ago so I had it available for my dividing head.

Jo

Edited By Jo on 08/05/2014 08:17:31

I agree with Nigel that a narrow body, light duty, 8" / 200mm Pratt Burnerd would be the ideal choice of four jaw for your Boxford. Its around half the weight of the standard version which, even if there were not more compelling reasons, would be a major point in its favour. A standard four jaw is getting close to the top end of what I care to haul out of the cupboard and heave onto the machine.

One such on a D1-4 mount is what I normally use for four jaw work on my Smart & Brown 1024 VSL. A machine of similar nominal capacity to your Boxford albeit much more heavily built and easily capable of coping with the mass of a normal 8" / 200 mm four jaw. The light duty Pratt Burnerd body is around 2" / 50 mm deep whilst the standard version is a little over 3", almost 80 mm, deep. The light duty Pratt Burnerd chuck jaws are essentially the same size as the jaws for the next size down (6" / 150 mm) four jaw so everything is that much more handleable and even small work can be conveniently held. Standard 8" / 200 mm jaws are very much on the chunky side so small jobs tend to either disappear or suffer badly from chuck-jaw-in-the-way syndrome.

My view is that in these sizes the standard style four jaw should be classed with the Chas Taylor three jaw as being for use when you need serious grip on a component. Not as a normal use resource.

Clive

Under drive Boxford's are quite common and have a 1-1/2" x 8tpi thread but this one has a D1-3 fitting so will need a D1-3 back plate. Buying a narrow body Pratt Burnerd is easy enough but you need add in the cost of a D1-3 back plate.

BobB