Actually a very good question. I think tolerances is the answer.
In a jacobs, all three jaws likely come down nice, tight, and
symmetrically, just from one chuck key hole.

In an import, there is likely asymmetrical slack/slop, and mebbe even some
camming, so that after a little operation stress, the "cocking" of the
initially-tight drill then releases, and the bit is actually *totally*
loose. Like a sloppy dowel pin that first wedges tight, and then drops
loose.

Three out of five times, my 5/8 chuck drops the bit--cuz I refuse to tighten
from all three holes!! Other than that, it runs pretty true.

It's sort of a game now, to see if I can make it thru one hole without
having to re-tighten the chuck.
--
Mr. P.V.'d
formerly Droll Troll
"pogo" wrote in message
news
"Leon Fisk" wrote in message
...
On Fri, 10 Mar 2006 17:16:09 -0500, "pogo"
wrote:
Why does a stock Corvette beat a Chevette in the quarter
mile?

They're both Chevy cars...

Yeah I know one is better than the other, but WHY is my question .
Better tolerances ? Is the design different ? etc ...