Fingerboard radius gauges that you can download, print out on card stock, cut out with scissors, and use. This article originally appeared in American Lutherie.
Initial appearance: November 5, 2021
Last updated: November 05, 2021
Copyright © 2003 R.M. Mottola
[This article originally appeared in American Lutherie #75. It has been updated.]
Everyone needs to check the radius of a fingerboard now and then. Commercial gauges for this purpose are available, but here are some you can have for free. There is one plain gauge and three slotted ones - one each for guitar, 4 string bass, and 5 string bass. The slotted gauges can be used to check a fingerboard with the strings on, although you may need to slacken the strings depending on where on the fingerboard you are trying to use the gauge. Each gauge has four surfaces, corresponding to the four most common guitar and bass fingerboard radii. The gauges can be downloaded below.
The drill here is the same as for the dot marker position gauges that appeared in American Lutherie #72 and are used in my book Building the Steel String Acoustic Guitar. To prepare the gauges, first print the pages onto card stock and cut them out with scissors. On the slotted gauges, cut the curves first, then cut out the slots. You will probably need to use a sharp knife to cut the top of each slot. Take some care when cutting the curved surfaces of the gauges, as these surfaces are the reference surfaces.
Lately I've been printing these and similar gauges onto heavyweight laser mailing labels (Avery 5526 or equivalent) instead of card stock, and then sticking the labels onto thin plastic sheet stock before cutting them out. This makes for a very durable gauge. If you use card stock or have a stack of labels you may want to make more than one copy in case one of your cuts doesn't come out just right. Be aware that a misaligned printer may make the copies bigger or smaller than the original and this will cause problems. Each gauge should measure 3.5" x 3.5". If not, try a different printer.
Gauges like these are simple to draw with any CAD drawing software, so if you need additional radii you can easily draw some more gauges yourself.
The downloadable copyrighted gauges are made available for non-commercial use only and may not be redistributed.