Joe,
Normally there is some kind of spacer between the inner races of two housed
ball bearings. The arbor shaft spans the distance between the two inner
races. If there was no spacer you could tighten the retaining nut for the
arbor (opposite blade end) so tight the inner races will be preloaded to the
point of early failure. If after the installation of new bearings the arbor
does not spin freely something is wrong.

Bob


"Joe" wrote in message
...
On Fri, 25 Mar 2005 04:48:48 -0600, "Bob Krecak"
wrote:

Joe,
How are you installing the new bearings. When ball bearings are installed
in
a housing you CANNOT PUSH ON THE INNER RACE or the hardened balls will
put
permanent dents in the outer race which will cause the bearing to fail
prematurely fail. When the bearings are installed into the housing you
may
only press on the outer race.

Good point Bob and a fact that I am familiar with. Check out that
Harbor Freight bearing puller set I am using to install the bearings.
I make sure the pressure is even and lubricate the arbor housing and
outer/inner bearing surfaces with high quality teflon grease I use on
my mountain bike bearings before pressing them into place. I also
heat the arbor housing to give a bit more clearance to the outer race
of the bearings when I press them in - a trick I learned from working
with my high performance model airplane engines.

Also, is there a spacer between the inner
races of both bearings (I'm assuming there are two to support the arbor)?
It
is possible the spacer is a little too short causing you to preload the
inner races of both bearings which can cause them to fail if the loading
is
excessive?

Not quite sure if I follow you here Bob. My procedure when installing
the bearings is to fully seat the bearing nearest to the arbor threads
on the arbor, then pull it into the arbor assembly by the outer race
of the installed bearing. That should cause no loading on that
bearing. I then pull the other bearing from the pulley position on
the arbor by grabbing the outer race and flush it with the pully side
of the arbor assembly. That could load the inner race of the pully
side bearing but that one never goes bad. I have also tried using a
round piece of hardboard with a 5/8" hole drilled in it on the outer
pulley side of the bearing to put equal pressure on the inner and
outer races and that did a real good job of seating it with I would
assume equal alignment of the races..

I don't think your dado head should be an issue unless something
you are putting on the arbor is out of balance or the head is too large a
diameter for the saw. Delta recommends only a 6" dado head be used on
their
Unisaws to prevent bearing wear.

That is pretty significant if a Unisaw can only swing a 6" dado then I
need to reconsider that 8" hunk of metal I'm trying to spin.

..Joe L