Blind bearings

[Mike Arman <armanmik@n-jcenter.com>]

Gerard asks "what's a blind bearing?"

Actually, it isn't the bearing that's blind - it just means you can't get
to the back of the bearing to beat it out of the hole it is in.

A blind bearing puller has a pair of jaws which fit through the center bore
of the bearing and expand - then you pull the bearing out of the hole - the
slide hammer is one way (remember you don't plan to use this bearing again
anyway, so who cares if it gets trashed . . . ), some have extra plates and
misc. fitments which are placed on other parts of the bearing housing and
pull against it - the bearing is the path of least resistance, so out it
comes. (Some are retained by snap rings - make SURE the snap ring is out or
the bearing WON'T come out!).

Another example of a blind bearing is the needle bearing for the end of the
mainshaft - it lives in the flywheel end of the crank. Procedure is to fill
the hole with heavy grease, insert a drift the same diameter as the ID of
the bearing, and hammer it. Pressure from the grease pops the bearing out
(most of the time).

To re-install, the suggestion of using a large socket is correct - however,
you'll probably find that the local plumbing supply store will have some 3"
or 3.25" pipe (80mm), and a length of that plus a cap to hammer on will
cost lots less than an 80mm socket - and you don't care if the $2.00 pipe
gets buggered up in the process.

When hammering (ouch) on a bearing to reinstall it MAKE SURE you are
hammering on the race that is the press fit!!! If the outer race of the
bearing is going into a hole, hammer on the outer race - hammering on the
inner race transmits the force of the frenzied hammer blows through the
tender, finely machined bearing surfaces - and you've just destroyed the
bearing. If the bearing is a press fit on a shaft, hammer on the inner race
(use a pipe to slip over the protruding end of the shaft) - same cautions
apply about hammering through the bearing surfaces.

A little oil and some heat on the housing the bearing fits into will help -
make sure the bearing is started EXACTLY SQUARE - it can start cocked, and
then you will get it maybe 1/4 of the way in and discover you've ruined the
bearing, the housing, and your attitude for the rest of the week.

Best Regards,

Mike Arman