Fret slots in radiused fretboard

tobinsuke

tobinsuke

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Hi. I just posted this question to the fine folks at StewMac, and I thought I'd see what some others have to say while I am waiting to hear back.
"So I bought the table saw fret blade and made up a good template (tenor uke scale) and sled. I set the height of the blade to a touch above the depth of the tang, and I was all set to go when I started thinking..... hmmm, I wanted to put a 12" radius on this fretboard (yes, I bought some sanding blocks as well) - if I cut the slots at this depth and then remove material from the sides of the fretboard to create the radius, then won't the slots be too shallow along the edge of the fretboard?

What is the accepted way around this problem? I can imagine cutting the slots deeper so that after radius sanding they are the correct depth along the edges, but I don't know if the extra depth toward the center of the fretboard would be a concern. I can also imagine cutting the slots to the proper depth, radius sanding, and then having to get the slots to depth along the edges by hand. But I am not sure how to go about that, and this seems like I would be re-introducing the human error factor that I am trying to eliminate with the table saw set-up in the first place. What do other people do to get around this dilemma? Thank you." tobinsuke
 
tobinsuke said:
Hi. I just posted this question to the fine folks at StewMac, and I thought I'd see what some others have to say while I am waiting to hear back.
"So I bought the table saw fret blade and made up a good template (tenor uke scale) and sled. I set the height of the blade to a touch above the depth of the tang, and I was all set to go when I started thinking..... hmmm, I wanted to put a 12" radius on this fretboard (yes, I bought some sanding blocks as well) - if I cut the slots at this depth and then remove material from the sides of the fretboard to create the radius, then won't the slots be too shallow along the edge of the fretboard?

What is the accepted way around this problem? I can imagine cutting the slots deeper so that after radius sanding they are the correct depth along the edges, but I don't know if the extra depth toward the center of the fretboard would be a concern. I can also imagine cutting the slots to the proper depth, radius sanding, and then having to get the slots to depth along the edges by hand. But I am not sure how to go about that, and this seems like I would be re-introducing the human error factor that I am trying to eliminate with the table saw set-up in the first place. What do other people do to get around this dilemma? Thank you." tobinsuke
Click to expand...

Cut the slots with your table saw maybe slightly deeper than you would if the fretboard was flat. Radius the board and then you can use a hand held fret saw to make the slots deeper on the edges. It is not difficult and since the slots are already in the board, there should be no further error involved unless you slip, just be careful and all will be fine.
 
With a 12" radius you are going to be taking off about 0.5 - 0.7mm or thereabouts to the sides of the fret board. You can cut the slot that much deeper if you like without worrying. Afterwards you then wick thin CA glue down that left over slot.

Or you can do as I do, and I imagine a lot of the other pros here and go a little bit deeper than what you would need on flat board, and then nip the ends of the tangs off each end of the fret wire about 2-3mm back from the edge. In ebony and other dark woods you can then fill the slot on the side of the fret board after it's been fretted so it looks like a bound fret board.

It also means that you aren't going to run into that problem that you figured on.

Did I say I hate having to hand cut any sort of fret slot?;)
 
Grab a compass and draw a 12" arc 2" long. Measure the deflection in the centre of the 2" arc. This is how much deeper you need to cut for everything to be fine.

If someone could do this I'd appreciate it. I'm working away from home and don't have a compass handy. I'm tipping it's an almost insignificant value.

EDIT:Ok Allen beat me to it.
 
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Much to go on

Wow. Thanks to all. Looks like I might want to do a little a prototyping before I settle on how I want to accomplish this. Which I guess brings me (newbie that I am) to another question... I'd rather not go through much ebony or rosewood on the road to figuring out what is you going to work best for me - I have a surprising variety of other scrap hardwood lying around though - any suggestions for a stand-in fretboard?
 
You don't need a compass, just do the math and it comes out like this:

If the radius is 12 in. (305 mm) and the width is 2 in. (51 mm) then the calculated arc height would be 0.04 in. (just over 1 mm).

arc height.JPG
 
Update

Thanks again, all. In case anyone is interested, the tech from StewMac who replied suggested cutting the slots deep enough to still accommodate the tang after radiusing (pointing out that a 12" radius over the width of a uke fretboard will not be much of a difference). He also suggested a dab of glue if pressing or hammering and then wicking a bit of CA glue - included a link to a past StewMac newsletter on the subject.
I am delighted at the help that is out there (here) for the asking; hopefully as I build my skills I'll be able to pitch in.
Still going to try both the "over cutting" method and the touching up by hand after sanding method on some scrap, as I think I'll learn more as I go by trying both (I'll save the tang nipping for a bound fretboard project down the road). And yes, I will use a compass - having experience as a machinist, it helps me to see a "print" even when I have the numbers.
Thanks again!
 
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