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Making a Compound radius

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Depends on the fret-board width difference between the nut end and last fret at the body, and the exact path of your sanding block is going. If you level exactly in line with the strings, it can be pretty subtle, like 9.5-10" at the nut and 11-12"" at the last fret at the body end. If you make a little more effort to exaggerate the path of the outer strings, it will make the radius difference between the nut and body end greater. You have to use radius gauges and check what's going on, so you don't sand more than you should.

I hated always having to make a real effort to keep radius sanding blocks lined up with the neck center-line while sanding with them.

I never did buy stew-macs wood radius blocks, because I made my own. But I wondered how straight theirs were, and thought they probably warp a little after a while. It's much easier to check a flat block, plus a longer block (13"-18") that is dead flat, makes a more buzz-free neck, than using 4-8" wood radius blocks that could very well have some kind of twist/warp that is hard to detect.

Of course I'm not the only one who feels this way, because stew-mac has come out with those sanding bars, long after they've been offering the radius blocks.

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Thanks for the replies!

The main reason I'm asking is because I'm far from happy with the results I get with the radius blocks.

It's almost impossible for me to make a 100% straight fingerboard with those. I'm trying to use very little pressure, but I always end up with some area of the board that is higher or lower than other areas.

I kinda figured out that pre-radiusing with a radius block and then make the board 100% level with a dead flat longer block would be more precise.

Because of the taper of the fingerboard, block sanding parallel to the centre line would be impossible... and if you'd go with the string path, you'll end up with a CR...

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@tsl: I once had a good idea on how to produce perfectly straight compound radius fingerboards. It is a method often used for shaping the profile of RC Plane's Wings. I did not try the idea myself, because after thorough research discarded the idea of a compound radius fingerboard and went with cylindrical fingerboards. The idea works like this:

1. Make metal templates for the both ends of the fingerboard, which have the desired radius and shape you want on each end.

2. Take a long fret leveleing block or a long and not too wide sanding block and sand along the run of the strings, until you have sanded the wood down to the metal templates on both ends.


Marcel Knapp!

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Making the metal templates should take about 10 minutes for every template. You cut it out from thin(about 3mm) metal with a a metal scissor(dont know the correct word in eglish) and sand it to perfect shape. This method would also work with a cylindrical fingerboard and would give you the perfect results you are looking for. There are many well-known builders which do their fingerboards with radius blocks though. I think practice makes perfect here. You draw a center line on the fingerboard and always guide your radius block along that line. Change the orientation of the fingerboard several times during the sanding in order to avoid uneven results. Sand down until the center line begins to dissapear. And always check the flatness of the fingerboard with a straight edge during the process. I have to admit that I did not radius a fingerboard myself though. But the method I described above is used by most builders and is recommended in most good books about guitar building. If you are not happy with your results you can still buy the fingerboards pre-radius from lmi or stewmac.


Marcel Knapp!

P.s.: Are you German or did you learn it school?

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