I know there are saveral "swing arm" machines out there that use large bed sanders, routers, even tablesaws to cut a compound radius.
I have a small shop(don't want to store a big fixture, and don't have a big enough sander), I like the idea of compound radius fretboards, and I do not wan't to sand them by hand with radius blocks.
I came up with this idea: It basically uses to radiused end pieces. When pushed across a router table(at the right angle) it will create a perfect section of a cone.
I also have the fixture tapered, to cut the f/b taper w/o needing to do doublestick tape twice.
The inspiration for this was reading that double bass makers do this by hand with a plane. This is basically the "handplane" way to do it on a router table.
The downside is that is is a little prone to user error. The way I see it if the bit is set to the correct depth(there will be a go-no-go gage built in) there will be no way to bite too much, but if used at the wrong angle a little too much meat could be left on.
If needed I have a touch up sanding block designed.(transparent grey in pic)
Don't know if this explains it easier, but I will basically need to move it across the router bit parallel to each string(which aren't parallel with each other) not an exact science. When doing the middle pass I will move it along the center line, and the outside passes will move along the line of the taper rather than parallel to the centerline.
I'm wanting input. Will this work? Has this idea already been done? If you were building it, how would you improve it?
I also made an excell spreadsheet, based on the stewmac formulas for conical fretboards if that would help anybody.
The spreadsheet was helpful to create the "ideal" radiusses for a given taper--> if you select the correct ratio between radius and taper your fingerboard will have the same hight in the middle and edges of the f/b all along it's length.
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