It occurred to me some time ago what a waste of
time it was buying a cheap bench grinder.
You know, the pony little things that tempt you
with a low price. Then, you get home and
try them only to find that they only have a 150W motor and slow down when you
start to think about using them. What a
waste of space!
However, (I thought), what about those nice
little angle grinders that they turn out so many of that they sell for peanuts
– well, very cheaply. These are typically
rated at 500W, rotate at 10-11000 rpm and accept a 115mm disc. They have fittings that allow the use of
cutting and grinding discs and they accept wire brushes, core drills, etc.
You have the options of buying a good quality item
or going for cheap and replacing more often.
In my location these cheap versions typically cost £15; the green one in
the photographs cost £8 and has completed 2 grueling days in hot sun of
virtually continuous running in order to wire brush lime deposits off my
swimming pool (as well as, more recently, cutting lumps of steel for which it
was patently too small). A drill mounted
brush was useless for this because hand drills typically only rotate at 1800
rpm on full squeeze of the trigger.
What, I thought, if I was to make a bracket
that would let me put the angle grinder in the vice to give me an extra hand
for working? That was it though. I thought
about it and then left it for a couple of years – as usual. Usually, by this time, someone else has done
the job, so I guess I won’t be the first with this type of adaptation. There
are a string of inventions that made millions that I may have thought of first.
This week I felt creative, so I slotted the
development of this adapter bracket into my crowded schedule.
I found that the grinders are supplied with a
handle that can be fitted in two opposite locations for left and right handed
use. This was an obvious site for
attaching my bracket. The handle is
fitted by means of a tapped hole on each side of the main case casting giving
the two locations. The holes are tapped
out to accept an M8 screw. The width of
the casting between the two holes I originally measured as 65mm (regretfully
using a tape measure and stupidly assuming that the distance would be a round
figure). When I came to fit my bracket
to the grinder,I found this distance to be between 67 and 69 mm depending on
the manufacturer, and I had to adapt my bracket accordingly. (It was also
necessary to remove residual “flash” from the case casting in this area to make
the fitting “snug”.
As I am without proper machine tools, the
models were all made with basic stuff like a pistol drill, vice, hammer, the
grinder and a welder. I know that most
people will have everything except the welder, but you could either
pre-fabricate and bolt together (not recommended) or find someone to weld it
for you – most garages have a MIG welder which will do a much better job than
my cheapy stick welder.
For my “A” model, I cold formed (beat it to shape
with a hammer in the vice) a length of 4mm x 30mm strap iron to wrap around the
end of the grinder. I cut a slot in
either side for fitting to the grinder and for allowing adjustment as the disc
wears down.
The slots were cut by drilling a hole at each
end and joining these up with the angle grinder, then finishing with a file so
that an M8 screw could slide easily along the slot.
Next, I made the bit that joins to this bracket
for clamping in the vice. I used 25mm square section steel for this and welded
the parts together. Actual sizes are not fussy.
Then, on the “A” model, I joined the two parts
together, but don’t do this yet.
I know that’s a weird angle, but I tried to
join the original sketches together. Never mind!
However, you can see the oversight as soon as
you get to grips with this view. The
tool rest runs into the bracket attaching to the grinder limiting access to the
left of the disc.
So, in the “B” model I improved this a bit by
welding a plate across the bracket and cutting away the surplus material.
You can see that the left hand side of the
toolrest is still slightly obstructed by
the new plate. The view is not quite right I know, but I don’t have a drawing
package and had to do these sketches in WORD.
If I make another I
will add a small plate to the left of the first modification, stepped backwards
slightly to clear the grinder body. Then
remove the surplus material
To hold the grinder in the bracket you could
use simple M8 screws, but I welded M10 or M12 wingnuts onto M8 screws and cut
these to length so that they just didn’t bottom in the tapped holes in the
casting. I allowed for a lock washer to
be used. (Take care to make off the screw ends nicely as the casting is
aluminium and would be easily damaged by hacked off steel screws,)
To adjust for different fixing centres or to
correct errors, you can put a double set in the fixing bracket if necessary – a
bit of fine tuning.
The above example increases the distance
between fixings.
Here are pictures of the “B” model fitted in a
small vice.
I guess that a manufactured item would be
pressed from something like 3mm sheet steel.
Well beyond my home capabilities.
Get in touch if you have any comments.
All the best.
Kev
