Model Engineers’ Workshop – July 2019

July 2019 31

Bearing Removal

result of trying to ingest part of a shield or
cage. This half outer was fi rmly embedded
into a blind hole without even any notches
for a puller, leaving no opportunities to
remove it. Presumably the bearing would
be removed by inserting a puller inside the
35mm shaft under normal circumstances.
Photograph 4 also shows the location of
the bearing some 50mm below the height
of the surrounding drum.
Realising that the only way to remove the
track was to provide some means to attach
something to it, I got my MiG welding set out
and welded a couple of pins to the remains
of the track. I then proceeded to break the
weld since this bearing was well attached.
I then tried a trick I had heard about
some time back from the classic car world
and applied a thick and deep layer of weld
around the entire visible remains of the
track. Photographs 6 to 9 show various
views of the welding, I make no claims for
a quality job here and I doubt it would pass
any welding examination. Care was needed
to ensure that I did not weld the bearing to
the hole and just ensure that the bearing
would never come out but a Dremel with
a grinding wheel fi xed a couple of those
errors. Some evidence of this work can be
seen in photo 10. The theory is that the
cooling of the weld bead should shrink the
entire bearing and thus loosen it. Plenty
of heat and thermal shock may also help
the process. Aft er a couple of beads were
laid down, I welded 2 scrap bits of studding
to the track and used a slide hammer to
successfully remove the whole lot.
Once the blind hole was cleaned up, a new
bearing was obtained off the shelf at the
local tractor dealer, somewhat to my surprise
and the drum and mixer reassembled.
Generally, we look upon the eff ects of heat
and stress being applied to one side of an
object as being a bad thing, but in this case, it
got me (and the bearing) out of a tight hole.
In a last case, I had to remove a 12mm
shaft sized bearing from yet another blind
hole. This bearing had also started to break
up but was still in one piece fortunately.
Lacking a puller to fi t inside the shaft , I
found a Rawlbolt (expanding bolt used
for bolting structures to masonry) slightly
smaller than the hole. This one was the
variety that has an exposed thread with
a nut to tighten it against the end of the
expanding part. As the nut compresses
the unit, it expands thanks to a simple set
of ramps. Enough force can be generated
to crack individual bricks in two! I then
inserted the expanding part into the
bearing and tightened it until the bearing
was fi rmly gripped. A second nut was then
added to provide purchase for my slide
hammer. A couple of blows and out popped
the bearing.
The expanding bolts come in a range
of sizes and intermediate sizes could be
achieved with thick shim I suspect. They
form a very useful method of gripping all
manner of holes provided no precision is
required and are readily available at DIY
stores. ■

Some Dremel work is visible upper right where I was too enthusiastic and welded bearing to

drum. The studding for the slide hammer can be seen as well

This shows more clearly how the bearing outer broke up into two

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