Make a disk sander

[jj777746]

I have wanted to build a disk sander for a while & looked at some really good examples on line (dozens) but I would like to know the best method of attaching the backing plate to the motor.I would really appreciate any information on doing this. Thanks .JJ.

[BobL]

The best way is using a custom made Hub that has a keyway and a grub screw that will firmly hold onto the mot shaft and sufficient width that will allow 4 - 6 screws/bolts to connect the backing plate to the hub.
The larger the hub the better chance there is of the backing plate going on straight.

A largish flat pulley that fits the motor shaft is a good alternative.
The backing plate can then be attached in the same way as to the hub described above.
This is what I did to attach the brake disc to the drive pulley on my BS brake.

http://www.woodworkforums.com/attachment.php?attachmentid=306946&stc=1

Am importantly thing is to get the to get everything aligned relative to the motor shaft.
Start by marking the centre of the backing plate and pre drilling the holes in the backing plate that will be used to attach to the pulley - try to get the as far out near the edge of the pulley and symmetrically arranged otherwise the backing plate will vibrate..
Put the pulley onto the shaft and leave a 1/4" or so protruding past the pulley.
Drill a hole the same size as the shaft through the middle of the backing disc and put the backing plate onto the small amount of shaft poking out past the pulley.
Now use a drill bit the same size as the other holes in the backing plate to mark the holes on the pulley.
Remove pulley and drill out the marked holes with a DP.

Any remaining wobble can be removed by spinning the disc and trimming the outer edge that same as you would on a lathe.

[jj777746]

Thank you for such helpful advice Bobl,you answered every question I had without having to ask.The robust method you advised is sure to endure all the rough treatment it will cop from me.Thanks again.JJ