To make this machine, take one low cost bench grinder, remove the wheels and guards and fasten it to a thick piece of softwood, which can be clamped to a bench when required.

The left hand guard can be replaced with a saw table. The one in the picture is made from a section of 4 inch aluminium angle. The hardest job here is to cut the slot for the blade. Take care to make sure the slot lines up with the final position of the blade.

The original large steel washers will be needed to mount the blade, but several half inch steel washers will also be required as the new blade is much thinner than the old grinding wheel. A small hole is needed in the blade to allow for the passage of the screwdriver when assembling the blade and the table. Remember the shaft thread is left handed on this side! Remember you will need blades with a half inch hole for this machine.

Water for lubrication is supplied by a tray cut from a plastic container. The tray has a thin plastic tube fitted at the end and is kept full by a trickle supply of water from a hosepipe.

Alternatively, you could fit two lap discs on the same machine. This would reduce the number of times that you would have to change the discs during a polishing operation. You can always use an electric tile saw to cut your rough, but this does create a lot of waste as tile saw blades are quite thick.
 

A splashguard can be made from a piece of UPVC window sill. This is cheap, easy to work and will keep you from getting too wet when you are working.

The splashguard is fitted to the main body using the screws that held the original metal guard. The old guard can be used as a template for drilling the holes.
 
 

The lap disks are mounted directly onto the standard half inch shaft with an aluminium backing disk for support. Extra washers are needed, as the disks are thinner than the original grinding wheel.

Water for lubrication is fed via a thin plastic tube, supported by a plastic coated copper wire. The tube is connected directly to a hosepipe. An inline tap, like the kind used for home brew siphons, makes a good regulator.
 

To finish off, a second splashguard needs to be made to keep spray off the switch and the cable. This splashguard has been removed in the pictures to make the machine easier to see.

It is also wise to connect a safety circuit breaker into the supply line, just to be on the safe side.

We have never had any problems with this machine, but other makes of bench grinder may be less well sealed, or require a slightly different approach to conversion than the one illustrated.