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Mask for Belt Sanding

Mask for Belt Sanding

by John Calkin

Published online by Guild of American Luthiers, March 2024


My 6×48 belt sander is my favorite and most used machines, though getting the most out of it didn’t come easy. It takes a knack to use one accurately, and that took years to develop. Perhaps most importantly, I learned to join plates and sculpt necks, saving myself scads of time over the years.

This tip is about sanding parts on nearly completed instruments. It can be dangerous because the plates are already as thin as desired. In this case I needed to take down the end blocks of a dulcimer to the level of the plates. I had already shaped the sides of the blocks using a disk sander and sanding blocks. I used a scrap of poster board to mask the plates as I took down blocks to meet the plates.

The end blocks weren’t that much oversize. A hand plane might have done this job as fast as my belt sander, But I never use handtools if a machine will do the job.

Whew! I cut it close on this one, but it’s OK. The back of this dulcimer was already thinner than I liked.


The block on the bridge end has to be larger to make room for some sort of string fixtures. There are also blocks inside the dulcimer to support the end blocks.


The mask doesn’t have to be fancy or cover the entire plate. Sanding the block is done in quick steps with visual checking at every step.


No sweat this time. All of the hand pressure on the sanding belt is applied to the block. I usually keep 80 grit belts on my sander. Sixty-grit would last longer and cut faster but the scratches require more work to remove.


The abrasive barely touched the mahogany on this end. Most belt sanders of this size come with a 9" disk sander attached, but right from the factory mine wobbled badly. It was also frequently in the way, so I dismantled it. I considered returning the machine to Woodworker’s Supply, but repacking it would have been a lot of work. They still sell this machine. If they haven’t improved I wouldn’t buy it again. Standing the belt 90 degrees to the supplied work table turned out not to be a big deal, so I didn’t miss the disk sander very much. ◆