Hi John,
Thanks for the reply. I realise most people seem to be from over that way, but have seen a few posts from this side, and there appears to be nothing equivalent to your forum catering to the Montreal community.
OD 4 inch Mild Steel or SG cast iron; I'm thinking just some sawn-off bar would be fine. If I can find someone local to do the threading then I have a good relationship with a local steel stockholder who would supply the raw material cut to length.
internal thread 1 inch x 12tpi UNF thread form with a 1-inch diameter close tolerance register x 0.2 inch long for the spindle register diameter
Thickness 1 inch - I can do all the subsequent machining for chuck register, countersinks and holes for mounting bolts etc. All I need is the internal thread and spindle register.