Official Luthiers Forum!

I'd like to get the info on compound radius fret boards as to your action heigths that you are getting and another advantages you think it gives and also you jigs for making the compound radius boards and what radius you are using at nut and tail.
How you are fretting them such as hammering or press and ect. And why you use them or why not if that's the case.

Good Morning Chris,

I use a router setup that I adapted from the Grizzly sanding type swingarm. I usually will setup for a 10" at nut to 12" to tail for electrics, I find this works nice and allows no fret out on upper register string bends.
I press my frets in. I believe that Stewmac radius is 10" to 12" at the 12th fret and 14" at tail?

Below is a link to my jig. The link of the prototype section shows how it is adjusted for compound radius.

Section 2 is not done as far as the building of sled and jig though. I hope soon I can finish this and revamp the other sections for more clarity.




http://www.mikrovisions.com/jig/index1.htm

Just my way of doing this
Hope this helps in giving some ideas on one way to get there.

Mike

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I'm outside looking in, just farther from the window than most.

My jig is very simple. I'll post a picture of it tonight or tomorrow. I can do single or compound radius in 2" increments from 10" to 20". I hammer frets.

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I didn't mean to say it, but I meant what I said.
http://www.brackettinstruments.com/

Very interesting Mike. Have you ever thought about a way of locking the arm swivel and routing lengthwise? But that's giving me some ideas. I've seen something simular in concept but is like turning it upside down and using a hand router. I think Rod True has one that's modeled after Marios. But the router table usage has me thinking. Thanks for sharing. I'm hoping this discussion yields some good info for us all.

I start with a handplane, and then just use a variety of radiused sanding blocks, and then blend them together with a sanding stick that covers the entire length of the FB, following the lay of the strings. I do a 10"-12" or 10"-14" on electrics, and 12"-16" on steel strings. I pressed frets for a while, but went back to hammering a year or so ago. Me like hammer. Bang.

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Mike

"The Dude abides. I don't know about you but I take comfort in that. It's good knowin' he's out there. The Dude. Takin' 'er easy for all us sinners. Shoosh." The Stranger

I'm interested in trying a compound radius but need a jig/fixture that doesn't take up a lot of room.

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Steve Smith
"Music is what feelings sound like"

Steve, you don't need a jig/fixture at all, especially if you just want to try making one compound board.

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Mike

"The Dude abides. I don't know about you but I take comfort in that. It's good knowin' he's out there. The Dude. Takin' 'er easy for all us sinners. Shoosh." The Stranger

I have done my last couple as compound, roughly 12-20, and I have no trouble doing it by hand. I rough each end on the belt sander and then use the sanding blocks and a card scraper to get it really close. The final step is a straight edge with sandpaper following each string path making sure it is straight the whole length. Basically, just what Mike just said! If I am working fast it is about 20 minutes or so. I am certainly not against a jig but it can definitely be done easily and quickly by hand. For the frets I press them in with the complete caul set from CNC guitar parts. I hand bend regular frets as well as I can before pressing and they seat very well. I have had trouble with the larger gold frets, I can't really hand bend them beforehand and they don't stay seated as well as I would like right off the bat. Pressing and CA'ing in place would solve that but you risk gluing the caul to the fret. I have been going back and gluing them which takes longer.

I like the fact that the compound board gives you a more even set of string heights at the bridge. You can get all of the strings at roughly .5 instead of different heights for the middle strings and lower for the outside with a regular straight taper. It always bugged me that the G string, the one with the highest tension (I think) was also the highest off of the soundboard. I have also noticed less buzzing and easier bending on these last few compound boards, I don't want to go back.

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Burton
http://www.legeytinstruments.com
Brookline, MA.

Well at my current build rate of about .75 guitars/year it looks like I don't need a jig

Seriously though I would like to try it on my next. Anything I can do to improve playability is a good thing in my mind.

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Steve Smith
"Music is what feelings sound like"

Yeah but why take away all that fun!

I hand sanded my last fretboard and I'll give you guys credit who do it by hand. It's just not my cup of tea. I like seeing the jigs as I have an idea of one I want to try and see if it works that can be adjustable. And shouldn't be much larger then a old carpenters wooden tool box. If it works out I'll be sure to show it but for now keep the jigs a coming if you have them cause I might just change my mind after see yours. No use in reinventing the wheel if I don't have to.
For a one off you could buy a radiused board with of the large radius you want and then put the compound into it. It would save you a little time.

Chris, there was a pretty comprehensive thread on compound radius fretboards/jigs for same a while back - here's the link Compound Radius Fretboard Jig.

Cheers,
Dave F.

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Cambrian Guitars

"There goes Mister Tic-Tac out the back with some bric-brac from the knick-knack rack"

Here's how I handled the adjustability factor - an extra long bed. I'm out of town right now but, best I recall, the radius varies from 10"-20". Depending on where you place the board on the swinging platform you can wind up with anywhere from about 10"-16" compound or 14"-20". I've got hash marks across the bed at 2" intervals so all I have to do is line the nut up with the desired nut radius.

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Wes McMillian
Santo, TX
http://www.wesmcmillian.com

Thanks for the link Dave, I remember reading that link a while back and for some reason I thought it was Rod True that made it but it was you. I've been aware of Marios design for some time and have thought about doing one like that. There is a drawing on one with that simular design but not using the bearing in the MIMF library that I found some time back. But it wasn't by Mario so I'm wondering if thaty's who came up with it first. I can't remember who it was and when. I'll have to look it up again. One question though, I always assumed that you ran the router length wise a pass and then moved the swivel and made another pass. Is that how you do it or do you move the router forward a little at a time and swivel and move and swivel?
Two questions, Have you made any improvements to it in the last year and a half?

A plane is a good tool for the job. Shaping the FB can be approached in a similar way to shaping the neck shaft, if you do it after the board is on the neck. Draw a center line and begin planing, working from the outer edges toward the middle. Always plane in line with the string path, starting at the edges planing parallel to the tapered edge, with the plane tipped outward a bit. Never plane away your center line, but sneak up close to it. Visualize the compound radius (like a section of a cone) you're creating as you go, and let that image guide the plane. Keep checking that the edge of the FB remains a consistent thickness down the length of the board, and keep measuring each end, and a few places along the length, with radius gauges. It really isn't important that the arch of the board be a perfect radius, or that it be exactly some specific radius at either end, just that it's a nice smooth curve, and that the surface is parallel to the string path. Keeping the edge of the FB a consistent thickness helps accomplish that (unless you want to deliberately put some twist in the surface). Proceed slowly and carefully. It will go quicker than you think, anyway. Finish by sanding with a long straight FB leveler (I use a carpenter's level), again sanding in line with the string path, as Burton said. Be careful that the arch doesn't drop off (become a tighter radius) near the edges of the board, as that will make it hard to seat the fret ends. If anything, the arch can be more arched in the middle and almost flat near the edges.

As with many guitar making operations, I would suggest doing several by hand before beginning to use a jig. In the time it takes to make a jig, you could do at least 10 FBs by hand, with equal or better results. Trust the Force, Luke!

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Todd Rose
Ithaca, NY

https://www.dreamingrosesecobnb.com/todds-art-music

https://www.facebook.com/ToddRoseGuitars/

I don't have this concept clear in my mind.

With a compound radius, do you want the center of the fretboard to remain the same thickness along it's length and the edges of the fretboard to get thicker toward the bridge end of the neck? Or is the opposite desired......the edges of the fretboard remain the same thickness and the center of the fretboard gets thinner toward the bridge end of the neck?

Seems the jigs shown would have the first affect.......keep the center of the fretboard a consistent thickness while the edges of the fretboard get thicker toward the bridge. What am I missing?

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Formerly known as Adaboy.......

I guess that's correct and one way to look at it but with the taper of the neck it might be hard to see the difference at the edge.

I found that discussion at the MIMF library and on 1/7/02 A Gene Downs posted a drawing of compound radius jig like Marios and Daves and Wes' design and said he had bulit it like 4 or 5 years earlier. Although he didn't have the bearings like Mario's and Dave's it's the same concept. His top router guide would move but he said he thought he would make the next one have the board move like Wes'. So maybe Gene Downs is the first one to come up with that design?
here's the link but I think you need to be logged in to access it.
http://www.mimf.com/library/fingerboard_radius3.htm

-What Burton LeGuyt and Todd Rose said. We're only talking abou a coupla thousandths
here anyway- it is easily sanded into the board, or even the frets, though the former is much
preferable. remember this is only the *difference* between what the nut width *sees*, and
what the saddle width does.. v small difference. Routers and stuff..? no, i don' think so.

I made one improvement to it. I added a couple of adjustable stays to hold the platform steady for routing - one at the front of the swinging platform and one at the back. I set the platform in one position and lock it down, then run the router up and down the slot once, then I move the platform a little bit over, then make the next router cut. Rinse and repeat. I have not felt the need to change the radii (sp?) at all, although the jig could be made adjustable fairly easily by providing slots for the bearings/shaft to run in so they can be moved up/down. Here are a few photos of the finished work unit with the drawers fitted (please excuse the poor woodworking quality on the drawers - I was in a rush, so I used glue and brads ). My version of the Williams style binding jig sits on the right hand end of the unit, and the compound radius fretboard routing jig on the left hand end. I found space at the front to mount a small vise that I use for nut making etc. also. Click on the pictures to see/download the hi-res versions.







I can clearly see the difference in a fretboard that's been compound radiused on this jig vs. one with simple radius. I'm not much of a guitarist, but I can also feel the difference when playing vs. my old Martin and a couple other guitars I have. The neat thing about it (as Mario has pointed out several times) is that fret leveling is a thing of the past. I have yet to take a file to any of my frets.

Cheers,
Dave F.

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Cambrian Guitars

"There goes Mister Tic-Tac out the back with some bric-brac from the knick-knack rack"

-No doubt that that the compond radius board is analogous to what the string sees,
but why, with due respect, would this translate to less fret-dressing, since the initial
fret-dressing, if correctly done, would (more or less) create a compound-radius board anyway? CW

The FB is tapered in width. Therefore, if the thickness at the centerline and the thickness at the edges are consistent down the whole length of the board, the radius must get smaller from the soundhole end to the nut end. That's a compound radius.

On a board with a simple radius (same radius on the whole board), if the thickness at the centerline is the same over the length of the board, the edges will be thinner at the soundhole end than at the nut end.

With a compound radius, the board can have a consistent thickness down the centerline AND a consistent thickness along the edges, OR it can have a consistent thickness down the centerline and get thinner or thicker along the edges, depending on whether the change in radius along the length "matches" the taper of the board or not. I like mine to have a consistent thickness down the centerline AND a consistent thickness along the edges, so I "match" my radius change to the taper. Doing it that way, I think, also makes it easier to plane, as I described: keeping the centerline thickness consistent and the edge thickness consistent is a good way to gauge the creation of the compound radius.

I'm not sure it's accurate to say the difference between a compound radius and a simple radius is only a few thousandths. It doesn't make any sense to me to put a simple radius on the board and then a compound radius on the fret tops. That makes for removing more material from the frets than necessary, requiring more fret crowning, etc.

On the other hand, if you have a jig or method for quickly creating a simple radius on the board, then it shouldn't take long to sand the board into a compound radius by using a long FB leveler (such as my carpenter's level) and some 80 grit paper, sanding in line with the string path. To end up with consistent thicknesses in the center and the edges, you'd have to carefully gauge the pressure of your sanding to be removing material mostly from the edges near the nut end.

Does everyone understand what the phrase "sanding in line with the string path" means? This is the crux of the compound radius. The contour that's created by doing this is the whole reason for making a compound radius. Each string needs to be parallel (well, not really parallel, because the string rises towards the saddle, but I hope you know what I mean) to the playing surface underneath it for optimum playability. That is, if you put a straightedge on the frets in line with each string, it will sit flat. That's a compound radius and I think it's obvious why that is ideal for playability. A simple radius (a section of a cylinder) will not do that, because the strings do not run parallel to the centerline. With a simple radius, you're putting the strings diagonally over the surface of a cylinder; the surface, then, is essentially backbowed under the string, so you have to make the action higher to play cleanly, just as you would with a slightly backbowed neck.

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Todd Rose
Ithaca, NY

https://www.dreamingrosesecobnb.com/todds-art-music

https://www.facebook.com/ToddRoseGuitars/

That clears it up Todd! I wasn't considering the width of the fretboard getting wider toward the soundhole. The taper of the fretboard was mentioned earlier and I should have grasped it.......but somehow I was thinking of a taper in thickness of the fretboard instead of taper in width of the fretboard and it wasn't making sense to me.

Thanks for that explanation!

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Formerly known as Adaboy.......

As promised, here's a picture of my radius jig. I told everyone it was simple. I use a 1/2" template guide and a 1/4" downcut bit. I believe I'll change it to use a bigger guide and a bowl bit. I think that will do the same job with a few less strokes. I done my first 5 with a plane, some sandpaper, a straightedge and radius guages.

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I didn't mean to say it, but I meant what I said.
http://www.brackettinstruments.com/

Dave,
I really like your setup or should I say your routing station. I like to save space and incorporate storage as you did. Nice job with that. I think this design would serve me best as I could just add it on to the end of my router table. Although it might work out better for me to use the the opposite swing like Woody's as I can have the top stationary router guide level with my router table .
Woody,
Do you find the need for the neat bearings like Dave and Mario use or will a few nylon washers do to keep down any binding if there is any binding. I also like the slot with a collar use as opposed to an angle guide. I also like simple if possible. That's a pretty good cost savings also. Plus I like the flexability to change to standard single radius although I probably will stay with the compound once I start to do them but still like the option if you know what I mean.
Does anyone know of Gene Downs? I think it might be appropriate to credit him with this design if he was the first to come up with it.

Clarification: My description above was about what the radii look like on a straight neck, just to illustrate the geometry. In the real world, whoever sets up the guitar will adjust the neck so that there is a bit of relief. So, what a FB with a simple radius really ends up meaning is that there will have to be more relief on the neck to get comparable playability, and the relief will be a bit uneven across the board -

unless, of course, the fret tops are sanded into a compound radius first, which, again, begs the question: why not shape the board into a compound radius before fretting? (I mean on a guitar you're building; I understand that sometimes you wouldn't because of maintaining originality on a vintage instrument.)

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Todd Rose
Ithaca, NY

https://www.dreamingrosesecobnb.com/todds-art-music

https://www.facebook.com/ToddRoseGuitars/