Fretboard Radius Blocks
All guitars, with the exception of classical guitars, have a slight radius on their fretboards. The radius gives the player a bit more comfort in playing. It also aids in the setup of the instrument. Over the last 60 years of modern guitar manufacturing, guitars have been made with all kinds of different fretboard radii. Each manufacturer seems to come up with a slightly different size radius. Some manufactures have used different radii for the same line of guitars of the years. Since fretboard and string radius is such an important part of guitar setup and playability, it is important to have the right tool to create this radius. A fretboard radius block does just that.
You might think that a complicated CNC machine is the only way to put a radius on your guitar fretboard. Well, that's not the case. Luthiers have used fretboard radius blocks to create fretboard curves long before CNC machines were even invented. A fretboard radius block is a rectangle block of wood or steel that has one side cut out into a concave radius. You put double stick sand paper on the radius side of the fretboard radius block and sand the fretboard back and forth until the fretboard is rounded properly. This will take a little bit of time and you may have to blow off the wood dust from your radius block a few times. While you are sanding, keep checking your fretboard with a fret radius gauge. You don't want to over sand the fretboard if you don't have to.
Since guitar fretboards are made with all different sized radii, there are many different radius blocks. I don't think that you need to go out and buy five different radius blocks because unless you build guitars you probably won't use them all. The radius is already sanded into your guitar fretboard. You don't really need a radius block to repair a fretboard. You do need one if you are planning on replacing a fretboard. I'd encourage you to look at what style of guitar you mainly repair: Tele, Strat, Les Paul, etc. Then you can buy whichever block works for that style of guitar. Until you get into building many different guitars, I don't think you need a full set of these. One or two radius blocks with do. If you would like more information about guitar fretboard radii, please see my how to set your guitar string radius article.