CHEERS LADS ,
I had to use this method of work holding as you see in the photo's i had to drill and counter bore three holes for mounting the plates on the index attachment close to the bore ,and the plates are to large to hold on the O/D, also there would have been problems drilling all the holes and not hitting the chuck jaws .
close up showing under cut
60 deg tapper i used a large centre
M8 counter sunk socket cap , head turned to 60 deg , the origanal 90 deg dose not work as good
And next my quick exspanding mandral,, chuck lump of what ever you have to hand ,as long as it has large O/D than the bore of the job.
turn to size ,and give it some under cut , the one in the photos is one i had lying about .drill and USE A TAPPER TAP ,DO NOT TAP ALL THE WAY, just about the depth show in the photo.The reson for this is so you have tapperd threads
next using a saw cut 2 slots , leave in chuck. cleen of rag from sawing
screw in your screw
just to show what happens as the screw is screwed in
This holder was used for another job,, but still handy for other jobs .
O/D and face tuned