Model Engineers’ Workshop – July 2019

(Chris Devlin) #1
July 2019 29


Bearing Removal


Out, Out Damned


Bearing


I


n the recent past, I have had to remove
three bearings from blind holes, none
of which was easy to extract. I hope the
following may be of assistance to anyone
else in a similar position in the future.
I discovered this fi rst method by pure
chance and although I have not seen it
published elsewhere, I cannot imagine that
it is unknown, but I hope to bring it to a
wider audience.
I had a need to replace a small shielded
bearing, shaft size 5mm, that was fi rmly
located in a blind hole. Although the
bearing was un an unhappy condition, I was
hoping to recover it for the short term until
a replacement could be found. The problem
of course was fi nding a means of removing
the 12mm diameter race which was fi rmly
fi xed in a blind hole. Photographs 1
and 2 show the object with the bearing
partly replaced for these photos, I had no
intention of returning the bearing properly
into the hole just for this article!
Aft er various fumblings all of which
risked damaging the shields, I decided to

apply a method that I had read about but
never successfully applied. In this method,
the void behind the bearing is packed with
grease and a tight fi tting shaft inserted into
the bearing to act as a piston. This is then
fi rmly struck, and, in theory, the bearing is
then hydraulically ejected from the hole.
As is all too common the case, theory and
practise departed on diverging paths and a
lot of grease seemed to appear everywhere
whilst the bearing remained fi rmly in place.
The next step aft er removing the
larger globs of grease was to remove the
aluminium shaft I had used as the piston
which immediately presented a new
problem. The shaft would slide out until
a certain point whereupon it stuck in the
bearing. Major cursing followed until light
dawned that this was maybe my salvation.
I then gripped the aluminium shaft in a vice
and proceeded to pull it out on the slide
hammer principle.
This removed the bearing from the hole
with no further damage. Once removed,
the reasons for the shaft getting stuck

With apologies to the Bard, Simon Davies shows his powers of perseverance


1


The shaft aft er being cleaned up. The thin walls
around the centre drilling are clearly visible

Bearing partly returned to blind hole

This shot shows some evidence of trying to remove the bearing by
other means

2


3

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