"Ed" wrote in message
om...
I'm considering purchasing a 5C collet chuck for my lathe. I'm
currently using 3 & 4 jaw chucks and want the added accuracy of 5C
collets. Having no experience with 5C collets, can someone tell me if
they will hold my work:

Sure will. Probably better than a regular three-jaw chuck. Certainly as
good. I've yet to have work come out (if I tightened the collet, that is.)

I work a lot with bar stock in the range of
0.7" to 1" diameter, in pre-cut lengths of 0.120" to 0.5". I need to
bore these pre-drilled pieces to ID's ranging from 0.5" to 0.8". This
is not production work - I can't build a specialized fixture or modify
a collet for each piece.

The collets will be much better than the chucks for that application.
You're doing stuff that approaches thin walls -- a regular three-jaw chuck
will certainly distort something with 1/16" walls. Collets won't do that.

I plan to have 5C collets in 1/64" sizes for my OD range. Will
standard 5C collets hold my work for boring?

Sure. If you look at the collets you'll see that the gap is slightly bigger
for the 1/8 increments, smaller for the 1/32, etc. At least with my collets
they are. The 1/8 multiples have about a 1/16 1/8" diameter range. But of
course, you don't get as good a holding all around as with the closest fit
to your work.

What I mean is, I don't
want to bore a step in the collets (I'm not doing production work) to
hold the piece a fixed depth in the collet. I'd like to have some
sort of internal collet stop that still allows the 3/8" boring bar to
pass through the center. Any help is appreciated.

Most modern 5C collets are threaded internally for an adjustable stop. The
stop however, would also block the boring bar. I've never seen the kind of
stop you're talking about. But it isn't that big a deal to make a tubular
stop that would allow the boring bar through -- however, if you think about
it, the stop's wall thickness would have to be no bigger than your boring
bar.
How about just using a regular adjustable stop and putting in a piece
of thin wall tubing to act as the spacer and still leave room for boring bar
to clear?

If you're thinkingin terms of one of the Bison 5C, spend the extra bucks for
the "adjust-throug" versions. The added accuracy and run-out reduction is
well worth the cost.

boris
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