Posted on August 11, 2021August 19, 2021 by Dale Phillips Conical Fretboard Radiusing Jig Conical Fretboard Radiusing Jig by Mike Nealon Originally published in American Lutherie #66, 2001 How flat does the top surface of a fretboard need to be? A good working estimate would be to equate the tolerance to the gap between the top of the 2nd fret and the bottom of a string fretted at the 1st fret. The tolerance must be less than this gap or the 2nd fret will come into contact with the string. With the bottom of the open string about .01" above the top of the 1st fret and about 1/16" from the top of the 20th fret, the gap between the fretted string and the top of the second fret is about .005". Making a hardwood board flat to within .005" is not too difficult using ordinary woodworking tools. The router table and movable plate described here will produce a machine-carved surface smooth enough to require only a minimal amount of sanding or leveling. Photo 1 shows the jig fully assembled, with the router. Photo 2 shows the jig partially disasembled to show the function of the parts. The conical fretboard made with this jig has a 10" radius at the nut, flattening to a radius of 16" at the last fret. The fretboard blank is 3/8" × 2 1/2" × 21", and is flat on one side. The finished fretboards are 7/32" thick at the crown, and taper from 1 11/16" at the nut to 2 3/16" at the 12th fret (12.670" from the nut). Become A Member to Continue Reading This Article This article is part of our premium web content offered to Guild members. To view this and other web articles, join the Guild of American Luthiers. Members also receive 4 annual issues of American Lutherie and get discounts on products. For details, visit the membership page. If you are already a member, login for access or contact us to setup your account.