Thanks again to everybody for their advice … very much appreciated.
btw, Ian, forgive my temerity in venturing to question the advice of somebody much more experienced than I, but wouldn't a 3 jaw self centering chuck be better for this operation than a 4 jaw? I am thinking along the lines of Rod's post above …I will be repeating this same operation from time to time, so as long as the homemade collet is aligned the same way every time it is inserted, it should be perfectly concentric every time . Or a meringue? (Scottish joke …)
FWIW I ended up today buying a 3MT – ER32 COLLET CHUCK AND FULL 18PC COLLET SET from RDG … the price of £114 inc vat and carriage seemed very reasonable compared to buying MT3 tapered collets individually. Also, this set will handle every size between 2mm and 20 mm, including imperial sizes, so I am well chuffed.
For the 7/8" tube, I will make a shop-made collet as suggested above by Ian and Rod and others … once again many thanks, and apologies for the weird change in font … no idea how that happened.
Edited By murrmac on 01/08/2014 18:10:41