MIMF

Here is the version of fretboard radiusing I am presently using. It is simple, it is labor intensive, but it works well. I will say though that the more elaborate types as presented by Martin Taylor and Mike Trobaugh are outstanding and maybe I'll build one someday when I'm tired of the 'back and forth' sanding approach.

The jig is simply 3/4" MDF with an 1-1/2" x 1/4" oak strip centered in the trough to raise the FB and allow for a side space in which most of the sanding dust collects. I simply center the FB on that strip.I have since tack-glued a thin piece of wood as a stop at the nut end and simply use a couple of thin pieces of double stick tape to hold the FB in place. I use a 20" radius for my instruments right now and pretty much any other sanding beam would fit in the trough. The one thing you can't get away from with either version when you want a different radius is the need for additional sanding beams ($$) or additional ridiused jig components and then you're dealing with removing the router, plus additional storage, etc....

I am considering adding a handle to the sanding beam just to make it easier to grab on to. Another thing I've found was that the full length sanding beams, if that is what you like, are the best. When I used the shorter ones I had a tendency to end up with tapered ends on the fretboard and the full stroke of the long beam eliminated that.

Thanks for looking,

This is exactly my method, but with a shop-made 16" sanding caul. Yes, put handles on it!

If you don't mind muscle power, here's an easy way to make any radius, including compound radius, and not buy any radiused sanding blocks.

Some of the lengths of material don't really matter, it just depends how much room you have.
You need a straight 5' long base. Could be a melamine shelf from home depot, or a piece of marble back splash, or even a straight hardwood board. About 6" wide is good.

Get a roll of 80 or 100 grit sand paper with the sticky back from harbor fright or where ever, and tape a 3' long piece to the center of your base.

get a 4' long two by four or hardwood board, plane it flat, and tape your fretboard blank to the center.
at each end of this carrier, attach a 3/4" thick section of a circle. It should have a radius of what you want, say 12", plus the thickness of your finished fretboard.

You can make these 3/4" "pucks" on a band saw or router or whatever, and I can explain it more if anyone wants me to, but it's pretty easy.

Cut the puck so you have an arc a little longer than the fretboard is wide. The "cord" of the pucks will attach to the face of the carrier, one at each end. The center of the arc needs to be the thickness of the finished fretboard above the carrier. I'm not sure what you call this line as part of a circle, but the line perpendicular to the cord and at the center of the cord is as long as the fretboard is thick. Put one of these on each end of the carrier. Double sided duck tape will work. A center line on the carrier will help you line it all up.

So then you just flip this assembly over and sand with the pucks sliding on the base and not hitting the sand paper. When it doesn't sand any more, you are done.

You can use layers of masking tape to fine tune it. Masking tape is about .005 thick.

If you want a compound radius, the pucks at each end just need to be different radius.
Determine the two reference radius you want, and the scale length
So let's say 25" scale, 8" at the nut, and 10" at the 12th fret.
The radius changes 2" over 12.5", or .16" per inch"

Lets say your pucks are 6" from the nut, and 12" from the 12" fret.
The radius for the head end puck is 8-(6x.16)+1/4=7.29"
The radius for the puck at the heel end is 12+(12x.16)+1/4=14.17.
If you really want to dial it in, your measurement should be to the headstock side of the 3/4" thick puck, because that's what actually rides on the base.

I just use a handplane and plane along the imagined string paths letting the taper of the board dictate the compound radius. If you plane the nut end to the desired radius and take full length strokes each time, you don't have to worry about whatever the radius ends up as at the other end.

I tape the tapered, slotted blank down to a chunk of marble clamped in the vice so it stays nice and flat. Once the board is radiused, I make sure the slots are still deep enough on the edges and glue on the bindings. I then have to flush up the bindings but it doesn't take too long. Sometimes I sand the board with paper on the edge of my straight level, again being mindful of the string paths, If I feel like I need to because I didn't get all the facets planed away.

It is a good idea to bevel the edges of the fret slots with a triangular file to help avoid blowing out as you plane. Just like you do to the edge of the board if you are dressing it by hand and planing across the grain. With fretboards, you are planing with the grain but some of the spaces between frets are pretty small. . .

Bryan,
It sounds like your way requires actual skill. In my family this skipped a generation.