Magnetic Spin Sander
© Frank Ford, 5/24/02; Photos by FF
When these rare earth magnets came on the lutherie scene a few years ago, Dan Erlewine shared with me an idea he had for using them as remote sanding blocks way down inside guitars. He fastened sandpaper to the magnet he stuck inside the guitar, and simply scrubbed away on the outside, the way you'd use one of those magnetic fish tank cleaners to wipe off algae.
I recently came up with a twist (pun intended) on his sanding method.
Scrounging around in my junk boxes, I found I had a ball bearing that was a perfect press fit inside this piece of PVC electrical conduit. So I made a 1/2" diameter shaft to fit the bearing:
At the other end of the shaft, I stuck a piece of plywood into which I had set four neodymium magnets, each of which measures 1/2" diameter by 1/4" thick:
To avoid having every little piece of steel in the shop drawn up inside this mechanism, I capped the end with 1/6" thick acrylic.
The inside "slave" unit is a similar group of magnets, but for extra holding power I added a second row:
On the bottom, I glued a piece of that coarse steel "shark skin" sanding sheet:
Now, I can hold my rotating power head against the side of an instrument, stick the magnetic sander inside, and sand away by remote control:
To avoid any scuffing of the finish outside, I hold the PVC section steady as I slide it gently along:
Inside, this little dervish spins at 200 RPM and sands away like crazy:
Just the thing for sanding off epoxy residue left behind by, er, "less careful" repairers. . .
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