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Fret Radius..........


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Ok so I already know that most luthiers in small shops use a pre-shaped block to sand down the radius when making a fret board.......

Larger shops use a twin arm jig thats motorized and swings the fret board across the abrasive to radius the top...........

But just how does one go about doing a compound radius, anybody have a clue?

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Did you try the Stew Mac website ? Go to : Fretting supplies : Fretting tools : Fret Dressing, Leveling and Polishing :

They have what they call "Wooden Radiused Fret/Fingerboard Leveling Blocks"

They create an accurate playing surface radius, quickly and without guesswork.

For compound radii, change blocks as you progress along the fingerboard.

Hope this helps you


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elementary my dear watson, with CNC milling machines, you can create any compound radius you want, they simply use a (usually 1/8") straight bit and a 3D milling program. The bit cuts literally hundreds of passes, then all that is required when completed is a couple swipes with sandpaper and you're done, I had to do this in the metal shop on aluminum parts a few times.

Any mass production shop has CNC equipment, and a compound radius board probably takes about 1 and a half minutes in a high speed machining center to produce, if you consider probably 1 minute part change, that equals 192 fretboard a day based on 8 hours, but I know most of those companies run shifts :D

Really, it's not so hard to understand when you consider the back of every neck we have is a compound radius from nut to heel, and those are all done on CNC machines.

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  • 4 weeks later...

Actually, it's pretty easy for a small time builder to knock out a few compounds. I use the blocks, myself, but I have seen the twin arm jigs. Just make the arms two different lengths. Make it like a swing with one chain shorter than the other, then swing it back and forth over a huge belt sander. I would build the belt sander into a benchtop, and build the frame over the top of it. By angling the top bar, and altering the uprights, any compound radius could be done. we had a jig just like this that we used to make the curves for wooden boat rudders, except we had a few extra steps in, as there were three different coumpound radii cut on top of each other for each side of the rudder, or daggerboard. I have seen wooden frames, with adjustible arms that look fairly easy to make. I wish I had made a couple of fretboards when I was working on the boats, but I never got the chance.

One other small safety tip. Always know where everything is, when you turn on a 42" belt sanding table. Especially if you have a 38" inseam, and are standing next to a 42" workstand, with workboots on, and there is a coffee cup sitting on the belt. I'll let you all guess where that thing hit me, and the worst guess is gonna be the right one :o

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