On Wed, 25 Nov 2009 04:18:14 -0800 (PST), Jim Wilkins
wrote:

On Nov 24, 11:36*pm, Ned Simmons wrote:
On Tue, 24 Nov 2009 20:38:12 -0500, "Ed Huntress"
...

One problem with tapered roller bearings, depending on how fussy you
are, is that the runout specs on standard bearings is pretty bad
compared to run of the mill ball bearings. And precision grade roller
bearings are horribly expensive and can be difficult to source.

Ned Simmons-

Does bearing runout matter as much if you finish the spindle nose -
after- keying and clamping it in place?

For my version you swap spindles rather than making precise threads
and tapers on the nose, so keying or at least putting the clamp
setscrews back in the same depressions is important.

Probably not as much, but keep in mind that a ball or roller bearing
is not in the same configuration on every revolution -- there's
relative motion between the races and the balls (rollers) such that
the balls (rollers) orbit at a different rate than the rotating race.
Consequently, my understanding is that if you monitor runout with
enough resolution you'll see a component of the runout that's not in
synch with the RPM of the race. As a practical matter, for a
home-built spindle, I wouldn't worry about the effect with normal deep
row ball bearings. In the case of tapered rollers I don't have a good
SWAG one way or the other without doing more research.

--
Ned Simmons