Official Luthiers Forum!

I'm currently building the compound radius jig. I'm encountering some problems. Has anyone made one? I would like to talk to Craig Holden ( its inventor) about it but I can't seem to locate him.

I have one. Besides a little chip out (which is managable once you get the hang of it) I haven't really had any problems with it.

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Brock Poling
Columbus, Ohio
http://www.polingguitars.com

I have the plans, but haven't built one yet... (i was kind of hoping someone else would start making them.... John?)

don't know what kind of jig you're talking about, but i made one that i think it was mario that thought up, and dave fifield(i think) has a thread here somewhere about how he built it.
fast, easy to build, great results.

Frank

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Frank

I use a CTH radius jig. I'm reasonably happy with it, but if I were doing it over again, I'd probably build the jig that Frank is referring to. I haven't used one like that, but it looks to me like a better way to go.

I think Craig Holden has dropped out of the radar. What problems are you having building the CTH jig?

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Todd Rose
Ithaca, NY

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

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

I can't find the 1 3/8 pipe specified in the plans. I have 1 1/4- I think it would be ok. Do you see any reason that I couldn't use it? Also, I don't quite understand the specifics for making the radius guides-there is something about the height being relative to the first set made.

I can't think of a reason why the pipe would have to be 1 3/8". But, if you want to stick to the plans and try to find some 1 3/8" pipe, I'd suggest McMaster-Carr, if you haven't already looked there. http://www.mcmaster.com/ All other things being equal, smaller diameter pipe is not as rigid, so that's one thing to keep in mind.

Another thought is that you might try carbon fiber tubes instead. I think they would be slicker, so that the router carriage would slide more easily back and forth. Just a thought. You could ask Jim Watts (Los Alamos Composites, a sponsor here, and an exceedingly pleasant fellow) about that.

I didn't build my own. I bought it from Craig when he was making them. I can't help you much with the radius guides. It's geometry - not one of my strong suits! I imagine it would be tricky to get that right, and I can tell you that on the one I bought, Craig didn't get it quite right. I have to shim up some of the radius guides by putting layers of tape on their bottoms in order to get fretboards to come out with consistent thickness down their centerlines. If the radius guides aren't precisely made, you could also end up with fretboards where the crown of the radius (the high point) doesn't run down the centerline.

Every time I go to cut the radius on a board of a new scale length or different radii than I've done before, I find I have to do at least a couple of test boards first (I make dummy FBs out of scrap hardwood) and do some shimming and tweaking to get the result I want. This is one of the reasons I'm not completely thrilled with this system.

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Todd Rose
Ithaca, NY

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

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

Hello, MD

I built my own CTH from Craig's plans, and everything went swimmingly. When you cut the radius templates, I think it is mostly important that they MATCH. I cut a fair (smooth) first piece and then used that as a template to rout the other three.

Also, I ditched the idea of using a shop vac for holddown power, and tapped a quick-connect right into the side of the fingerboard table, so I could hook up my vacuum pump. Weatherstrip the table to seal the vacuum.

1 1/4 " copper tube might have an O.D. of 1 3/8, but I wouldn't worry about it. I used 1" tube, 'cause that's what I had, and it works fine. Larger OD might roll a bit easier, but I'm not looking to extend this project.

By the way, you're not limited to FB radiusing: Tom Humphrey used his "Craig Device" (that's what he called it) to mill the curve on his head and tail blocks. He also put a very low, almost unnoticeable, rad on his fingerboards, but he got the device originally for head and tail blocks.

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Dan
http://www.acme-archtops.com

Right, but if you're doing a compound radius, then the two guides of one radius and the two guides of the other radius have to create a compound radius with the same peak height, or else the board will be thicker (measured at the center line) at one end than at the other. That's where the geometry of making the variously radiused guides gets more complicated. Or maybe it's simple if you're good at geometry, but, as I said, Craig didn't get it right on mine.

I like to have my FBs not only consistent in thickness down the centerline, but also along the edges. You can do that with a compound radius on a tapered board, but, for me, it takes some trial and error (trying different radii and somewhat different positioning of them on the jig - closer together or farther apart) when I'm doing a new board with different scale length, taper, and/or target compound radius. When I'm trying a new combination and the guides haven't yet been shimmed to give me equal thickness down the centerline, then that's another variable I have to work out. Soon, I'll have all the shimming figured out so that all the guides will produce the same thickness in the middle of the board, and then I won't have to worry about that part any more.



That's a good idea. I've been thinking of converting mine.



Hey, now you're getting me thinking! Cool!

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Todd Rose
Ithaca, NY

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

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

Ooop, yes, Todd

Compound radius, terra incognito (incognita?) for me.

Listen to your Todd, compound people.

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Dan
http://www.acme-archtops.com

Thanks for all of the help. I went ahead and used the 1 1/4 tube. That's cool what Thomas Humphrey was using it for.

If may be mistaken, but I think chain link fence rails are 1 3/8" in diameter? I'm not positive on that! They are 10 feet long with one end that is reduced in diameter. Just something to look at next time your at the the Blue or Orange Borg!!

Mike

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

You are exactly right. I picked up a 10' section for $11 and it was off to the races.
Thanks,
Matt

You are welcome!
MK

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