Sandpaper for a luthier dish - and making a luthier dish

[btberlin]

There are dozens of instructional videos on how to make your own luthier dish out of 3/4 inch medium density fiberboard (MDF). The latter is readily available in big-box stores, usually in 2 foot by 4 foot pieces (as well as 4 foot by 8 foot sheets). If you select the 2 x 4 piece, you can have it cut in the lumber department to two 2 x 2 foot pieces, perfect to make two dishes, one for the top, and one for the back. I used a brace template for the curve that i wanted to put into the dish, transferring the curve to a pair of runners for the router jig used to make the concave shape (see any of the jigs featured on U-tube and elsewhere). The brace template was cut to a full-sized pattern, which i had printed at Staples (less than $7 per sheet for a full-sheet print - cheapest I have found). I cut out the pattern, and glued it to a piece of lumber with 3M type 77 spray adhesive. The curve was cut on a bandsaw keeping slightly to the outside of the line, and then faired with a spokeshave and sandpaper. That became the master to create the runner for the router jig.

After making the dish, i sanded it with an oscillating sander (80 grit) to take out tool marks from the router bit, then sprayed it with 3M type 77 spray adhesive. Now, here's the saving money part - you can buy 80-grit sandpaper with a rubberized backing from Home Depot (and online I suppose) made by 3M. It is called Pro Grade, and it is great stuff. Sanding dust is easily brushed out of the grit. It takes 4 sheets to cover the 24-inch dish. See attached photos. This saves the cost of a 24-inch diameter sanding disk, which runs over $30. Three sheets of Pro Grade are less than $4.00.

It comes in a wide range of grits, up through 600. The 600 grit is useful for leveling a WB sprayed lacquer, such as Target EM 6000, dry. The EM 6000 powders beautifully, and the white dust comes right out of the 600 sandpaper with a piece of cloth or a brush.

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Bert

Hey Bert,
Welcome back. Nice tutorial. Thanks.