An Assortment of Useful Stuff: How to Convert an Angle Grinder to a Bench Grinder

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,)