Ultimate Fretting Caul Set


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The Ultimate Fretting Caul set – a 24 piece set of fret press cauls to allow you to fret any radius between 6″ and 24″ – with a brilliant piece of ingenuity when it comes to sizing of the cauls from David Collins of Ann Arbor Guitars.

This set is designed to have a constant change in sagitta between sizes rather than a constant change in radius. What this means is that if a particular fret caul radius is a little too far off the radius of the fretboard, you simply grab the next size caul and try it. The cauls are spaced roughly 0.003″ apart so there’s always a size that fits.

From Dave Collins of Ann Arbor Guitars:

“The traditional approach is of course to say if you are fretting a 12″ radius board, use a 12″ radius caul. My experience however, places this practice to be one of blind faith in numbers and specs, with shortcomings easily overlooked for convenience. By and large, for the majority of fret work seen in real life, these specs rarely end up so perfect. From the thickness of the wire, to the glueing, leveling, and sanding of the board, it is quite rare for a 12″ radius to be a true 12.0” radius, even when it comes time to install frets on new construction.

For anyone who does refrets or uses compound radius boards, the schism between spec and reality become even more obvious.

So my approach is a preference to abandon the false comfort of tidy round spec numbers, and instead shift toward a series of narrow increments. This means the radii these will be cut and marked as will not be a nice neat series of 10, 12, 14, 16, etc. Instead I would prefer a series of consistent increments spanning whatever range may be typically encountered.

I write this long preface because at first glance the odd numbers they will be spaced to could no doubt be received as discomforting when they do not line up with the precise (but rarely real) numbers we like to list as specs. In practice however, I find the neat round numbers to only be of false comfort, and when pressed to the board don’t necessarily provide the best palette of choices to work with.

Instead I’ve come up with a series ranging from around 6″ to 24″, with the focus on incremental change in the sagitta, or the height at the center of the radius. The geometry gets a bit complicated, but the current layout is arranged to set increments ranging from approximately .002″ in the shallower range (slightly less when viewed from perspective toward the nut, slightly more as it widens toward the extension), up toward .0025″-.003″ as you approach the shallowest radius of 6″.

The end result will be that if you find yourself pressing against any radius not perfectly matching the caul (which in reality pretty much amounts to every guitar or caul set you’ll ever work with), you will use the next smaller radius. The difference in the center is then automatically compensated for by the slight bit of slop that exists in just about every pressing system. At the widest gaps between radii, the caul need tilt no more than 1.5° max to press the center fully down that last ~.002″ once the ends are seated.”