I realised a long time ago that new motors were expensive so when
I saw my local DIY store selling bench grinders for £20 I knew that 1/2 horsepower 3,000
r.p.m. motor was going to be
useful. Since both a 6 inch trim saw and grinder need to run at around 3,000 r.p.m. I
figured I could build a real combination unit.
The base is sheet ply with glued and screwed 6x2 timber upstands to support the bearings
and raise the trim saw so that the drain hole works - only in theory, it is usually full
of gunge. The shaft and bearings are a Picador unit - a good tool shop should be able to
get them. Be sure to get the direction of rotation right, spinning the motor should
tighten the nuts on the shaft if in doubt try it first without the wheels. The whole base
is sealed with 2 generous coats of fibreglass resin - left over from abortive attemps to
mould fibreglass spray shields. The spray shields are bent up from 22swg steel sheet from
a cardboard template and mounted using the eyeshield mounts that came with the grinder.
Water is fed to the wheels via car windscreen washer tubing and jets from a can which sits
on the shelf above the unit. A recent refinement has replaced the tube with IV tube and
clamps giving an easily adjustable flow but I don't recommend a hospital stay just to get
the bits, I was there anyway!
In my eagerness to get cutting the plans for a folded steel water tray with detachable
rests gave way to the cut up gallon oil cans seen in the picture - not pretty but until
now nobody else has seen it.
I have added a belt guard, more sheet ply screwed to the bearing supports.
In hindsight I should have mounted the bearings on the front of slightly taller timbers to
give more hand room around the wheels - apart from that it works just fine and has cut
many hundreds of stones.
Remember - always run a wheel dry before turning off the motor and stand to one side when
turning the motor on - an out of balance wheel will vibrate like mad and can explode - not
nice!