Need help with chuck design

I'm thinking of making a collet-like chuck. It would be collet-like in
that it would have a fixed size and have fingers that close to hold.
Unlike a collet, it would taper to the front and have a threaded tapered
sleeve over the nose:
formatting link

There are two versions shown, one with a 2 degree taper and one with 5
degree. I can't decide which is better using my standard TLAR (That
Looks About Right) methodology. The lesser taper has more mechanical
advantage, but requires more turns of the sleeve. Similarly, a fine
thread pitch has more mechanical advantage, but requires more turns.
Using the goals of .004 change in the bore with 1/2 turn of sleeve, I
can use 2 degree taper and 9 tpi or 5 degree and 12 tpi. The 2 & 5
degree alternatives were just picked out of the air using TLAR. The
pitches resulted from the 1/2 turn for .004 close goal.
The biggest uncertainty is which, if either, will provide adequate grip
for reasonable torque on the sleeve. The application is to hold a buff
or wire wheel, so the needed grip is not that great.
I've got the feeling that this is the kind of thing that I could make a
lot of versions of if the approach was to just try something (i.e.,
TLAR). I think that I need a more analytical approach, but I don't know
what it is.
As always, your expert advice is greatly appreciated,
Bob
BTW - the drawing was done with DeltaCad. Anyone know how to add cross
hatching? Also, to get the jpeg, I PrtScn'ed the DeltaCad window,
pasted it in Adobe Photodeluxe, cropped it and saved to jpeg. Any
better way?
Reply to
Bob Engelhardt
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