Like the title of the post suggests it, this one's about truing and routing the bearing edges to their final shape.
While doing it, I really felt like I was finally working on a musical instrument. I don't know, looking at the edges getting nice, smooth and flat, and thinking about the head resting evenly made me feel like the whole restoring process was even more worth it.
Here's how the bearing edges looked like when I got the drums. They had been recut, since SONOR drums from that era had round bearing edges, but the job was poorly done.
I started off by checking the height of the shell using a template, based on the lugs drill holes. I actually took the smallest height and removed 3 mm both sides. After sanding, edges should be flat and parallel, assuming the drill holes are perfectly aligned. Which is the case. C'mon it's German engineering.
The idea is to sand off just enough material to be able to route fresh bearing edges.
Afterwards, I built a router / sanding table with birch plywood leftovers (from my uncle's carpentry company).
As you can see on the picture, I'm using a 24"x18" phonic plus shell as a reference for checking trueness. By the way, the shell will be part of a next project that I - of course - haven't planned yet.
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The white marks help me sanding flat until enough material is removed. |
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This is a - discarded - large piece of sandpaper from a wide belt sander. Very convenient. |
The re-cutting steps
1. Existing bearing edge
2. Edge flattened on the sanding table, 2 1/2 plies wide
3. Outside round out to 1/4th of the 2nd ply
4. Inside 45° to 1/4th of the 2nd ply
5. Careful finishing by hand, leaving a little less than 1/2 ply of head contact.
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Outer roundover, using a 1/4" radius bit. |
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Still a tiny bit to go to get to 1/4th of the second ply |
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The inside 45 was done with a chamfer bit, working with very small height increments (0.25 mm) to ensure the cut doesn't go too far.
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Finishing by hand, with P150, P240 and then some polishing with scotch brite |
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Always very complicated to take a good picture of the bearing edge, but it gives you an idea how nice it is now. |