My bandsaw got to the point where it was very tired, the guides needed replacing, bearings in the wheels were struggling and it was a 3 wheel variety with an unusual blade length. All in all time to go, but the motor was quite an impressive 300W and 1400rpm.
I did some searching around and realised that I could buy 6″ (150mm) diameter sanding discs with a sticky backing at a good price. How hard could it be to make my own sanding disc?
The motor has a flange and bolts to attach it to a plate – this actually made it easy to make a basic open structure from 3/4″ MDF.
The basic structure consists of a baseboard, 2 side boards that are tapered at the front to allow the sanding bed to rotate and an upright bulkhead that the motor bolts to.
You will need to design this structure to suit the motor and disc size you plan on using.
The basic MDF structure is glued together with Titebond and screwed – note where features are such as bolts for holding the sanding bed and avoid these when placing screws.
The sanding disc is again made from a piece of 3/4″ (roughly 18mm) MDF. This is fixed to the motor with a boss made from aluminium that has a bolt to lock it onto the motor spindle and holes that allow screws to pass through this boss and locate in the MDF disc. I was careful not to have all fixings on the disc locate from behind so as to give a solid font finish where the sanding disc will attach.
The disc was cut roughly to size on the bandsaw and then once attached to the motor and sanding machine base I machined the edge true using a chisel and sanded to a clean finish – this ensured the disc runs true and minimises vibration.
In the final machine assembly the bolted hub on the motor can only be accessed by removing a panel that ensures fingers and debris cannot be dropped into the space behind the sanding disc.
With a sanding disc it is really important to follow the basic health and safety rules in the workshop and use a dust extractor and a face mask. I use both as the dust extractor only collects so much of the dust created by a machine like this.
The dust extractor pipe is a push fit into the hole underneath the sander and you can see above this a simple wedge shape duct focuses the extraction onto the disc.
The sanding discs are available from RDG in a number of grits: RDG Sanding Discs
Overall this machine works really well, the discs stick really well to the MDF, but I would varnish the MDF as this will help with removal of the discs and it will harden the MDF if you use an exterior polyurethane varnish. If you have trouble removing the discs then warm them up by first sanding an old piece of hardwood. This makes the glue hot and softens it.
Old adhesive can lose it’s stickiness and so it’s ability to hold on a sanding disc.
This is a quick way to revive those old discs and make them workable again.