Thanks for your input Chaps, some I'd thought about some had passed me by.
I was a little puzzled why they are described as clamps then I realised that they didn't' have the tong, groove and keep to stop the jaw tilting, so I guess that's why they call them clamps, and not vices, because of this I think you must have to use them differently to keep the work square. I'm still thinking about the best way to configure the screw:- on centre, above, or below, what I do think though is that it must have quite a sloppy fit to allow it freedom to tilt and push the work up against the square fixed jaw and keep the work square.
I had a good look at the ones on ebay and the odd ones show signs of being modified.
Jason I did buy a pair from Uncle Ketan but was disappointed to find that they were far from being a matched set but to be fair to Ketan I didn't stipulate that I wanted a matched pair.
I've come to the conclusion that they would be most use as a matched set, so I've drawn them up as a pair tied together with some spacers plus I've put a groove down the side for clamping and I've left the end square I'll also add a V on the inside of the jaw for round bar and I'll put a V goove along the bottom of one so that it could be used as a V block not quite worked out a clamp for this yet.
Her's whot I've roughed out. Don't know when I'll get round to making them as I'm busy making the motion bracket for the loco I'm building.
Cheers
Stew

Edited By Stewart Hart on 27/11/2017 19:16:31