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Raduis Jig For Fingerboards...


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OK..a two part post.

1. When I used to make guitars many years ago...the biggest problem I had was making a radius on the fingerboard. In the end I made my own kind of jig/tool...which works perfectly. I still have these tools today..

Anyway...I made it using hardened steel...I had a radius cut in the steel by my father - and two locating holes taken from where I wanted them on a block of wood...I then cut a slot in the block and inserted the steel scraper...and screwed in place...I did it this way for easy removal for sharpening.

The centre point on the radius sat at the flat of the block of wood. The reason for this was simple...so when I had cut down the radius...I knew I was done..because the block of wood would then be sliding on the fingerboard surface...and would no longer cut.

The tool was used by moving it back and forth along the length of the fingerboard...it always came out leve...as when the block of wood touched the surface...and high spots would by taken down until it cut no mre...so everytime I had a perfectly level fingerboard...a diagram below is included.

I have 10 blocks ranging from radius 12" to 22"...they were perfectly simple...and because it was tempered hard steel..it could cut anything..ebony, maple you name it...it also reduced the need for much sanding...here is a diagram which explains it better:


This leads me onto the second part. On my two projects I am starting I want a compound radius...I intend getting a blank...and starting with the tighter radius work my way down the fingerboard...but I am nt sure how this will work as I am concerned about too much taper off at the end..

Any of you know any decent tips for compounding...I know you can get these ready made from stewmac...but as always, I like to experiment and do completely myself...



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Ian, those look cool and I think that to start the radius should be OK, but I don't think they will work fine on the finishing part, if by any chance you twist your hand, the blade catches on a corner is start up again part.

On the compuond radius, you will start with the say 16 on the hole board and then once done with that use the 10 from the top down I say till the 10-12 and feather down. Since you got all those different sizes you coul start with whatever you want at the bottom and every say 5 frets change the size like in 20-18-16-14-12-10. until you reach the compund that you want.

Good luck!

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SOrry...I forgot to mention that when 'using' the block...it was located between two side battons...the fingerboard was screwed down on the excess parts within the jig...you then just moved the tool back and forth...you knew it was dead level as the flat of the block was then on the board...and becasue the block was 6" long...there was enough flatto preven a see-saw motion...

it was impossible to cut deep because the very top of the radius was level with the block surface...

When I did ebony...I never needed to sand afterwards...because it was tempered steel...the edge was doing the cutting and finishing...it was glass smooth. When I do these projects I will include pics of this process..perhaps even a quik vid of it working...

The only wood I needed to give a very fine sand to was rosewood...but it was hardly worthit - the trick is in the stregth of the steel...and to date...I have never needed to sharpen thiose things and they are over 18 yrs old now..

I still need to work on the theory of the compound...but thanks for your tips on that...most usefull - I was going to start at the nut end...so good info from you...thanks..



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I built a router jig a while ago for doing compound radius boards. There's a few pics on the web of others attempts at it but some of them don't look right to me. It's hard to explain but some of them look like they are relying on the jig "flexing" while adjusting. The design I'm talking about uses two side pieces that are about 10" and 16" connected to a frame. The router sits above. I'm not going to be able to explain this very well but if you imagine two different length boards (10" and 16") connected to a common axle (and connected together at the top by a board that the fretboard rests on) - when it rotates, it will have to flex or it would bind. The design may work but it just seems flawed to me.

Anyway, I found another design in an old issue of GAL. I think it may have been issue #62? It's a great design but unfortunately, the article gives incorrect angles. If anyone decides to build from it, you'll need to figure out the correct angles before building. I checked with the people at GAL a while back and they agreed that the information in that article was wrong but I don't know if they are including a correction in future copies or not. I was able to get it worked out and built it about a year ago. I've used it many times and consider it a valuable tool.

There's also a group of people who feel that doing it by hand (sanding though) is just as easy. I think I'd agree but when it comes to ebony, I would much rather use a router jig and do some finish sanding as opposed to doing it all with sanding.

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  • 2 years later...

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