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Strong enough for clamping
Molded Magnetic Cauls
© Frank Ford, 8/11/02; Photos by FF

In a recent discussion with a magnet supplier, I learned that adding a steel bar across the opposite poles would "complete the magnetic circuit" and make for greater holding power for pairs of magnets. So I came up with this simple way to encapsulate pairs of magnets to make side reinforcement holding clamps.
I superglued tiny strips of pearl and abalone on the back side of my steel bar to mark the poles, mostly just for fun.
And I made up a little wooden mold, with two compartments for the two lengths I chose for my steel bars. I spaced both pairs of magnets evenly, but I thought it might be handy to have one long and one short bar.
Then, I filled up the mold with some West System epoxy. To avoid having it "go off" too rapidly, I used half the usual amount of catalyst resin
After the epoxy set, I simply chewed off the wooden mold.
And cleaned up the edges on my marble sanding plate. I must admit I tried the belt sander, but, of course, the magnets immediately stuck to the table!
As I trued up the faces with a double cut file, I didn't have to push downward at all. . .
So, now I have a pair of magnetic clamping cauls of different lengths, each with matching 5/8" diameter by 5/8" thick neodymium magnets.
They're strong as the devil, and can easily hold a side reinforcement inside a guitar.
The longer caul just bridges the entire side to give a solid flattening effect as the patch inside is glued in place.

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