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How can you be sure that the fretboard radius is ok? Cant you just sand it out until it seems ok or will you revome too much wood in the end?

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How can you be sure that the fretboard radius is ok? Cant you just sand it out until it seems ok or will you revome too much wood in the end?

by "ok" you mean continual? smooth? the desired radius and not another ? you can make guages, or buy a set to check it.

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ok I mean correct to what you want it the angle and to be smooth and continual...I would like it to be composite as well...9 inch radius to the top and 16 to the end. Does it sound a good idea to make two sanding blocks that will are of the desired angle and use it to sand the top and the end and then just smooth out the difference?

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the curvature of the fretboard is measuered in the lenght of the radius of a circle(just think of the FB as part of a circle). so the longer the radius the less profound the curve is

Whith that said. having an acurate radius by hand is not the wa to go, you dont have to buy the blocks, just take out your trusty compas and draw the desired radius on a block of wood. or you can buy one from stew mac for 8 bucks.

and i beleive thats what you do to get compound radius, except you smooth it out with the larger radius sanding block

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I see...so I will take a piece of wood and draw on it the radius needed cut it and glue on the edje of it a rough sand paper. Then I will take a block of wood and roughly shape a curvature in it and use the piece of wood to make it exact to the nessesary curvature. Repeat this for two blocks. Sand with the first block the first frets where a steeper curvature is needed ( 9 inches radius) and then sand the rest with the other block which will be wider and more flat and it will be passed over the area of the 9 inches curvature a few times to smooth out the difference.

If more smoothing out is needed logicaly a fine sandpaper will do without harming the overall smoothness and curvature.

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Please let us know how this turns out. I recently built a router jig to do this. The degree of precision that is required on a fretboard scared me away from trying to do it all by hand. I have read that someone claims to have developed the skill to create a compound radius using a small plane and does it all by hand that way. I don't have the time to do that nor would I have the time to do one with sanding blocks - that's why I went with the router jig. It still takes a while but it comes out very accurate.

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how do you do it?...do you rout wood out at differend depths making a square pyramid and then sand out the difference?

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It's difficult to explain. I've seen some simple jigs and some more complex jigs. Mine falls in the complex category. Basically, the fretboard rotates in a conical fashion and the router slides accross the top - making many passes. There's a little sanding required after the routing but it's not for the purpose of changing the radius - just to smooth everything out.

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its not that slow or difficult by hand... i planed it roughly first then sanded with a radius block. it was all pretty quick

Mike

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Oh, sorry mike - I wasn't talking about you - I didn't even realize that you had made one. I was talking about some article I had read somewhere. Some old-timer woodworker - I doubt I'll be able to find that article again.

Anyway - if you decide to do it by hand (sanding) - be sure to have a precision straight edge handy and check it often. Please post pics if you are able.

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It really isn't that difficult to do by hand. But another way to do it is on a belt sander. I rough the radius in on both ends and then use radius blocks and glass to finish up. Give it a few trys and you'll see that it's not too hard.

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If doing it by hand with a radiused sanding block I would sand the entire length of the fret board with the larger radius then continue with the smaller one.

I think it would make things harder to stop halfway down and then do the rest with the smaller radius.

So, radius the entire thing to a 16" then continue down to a 9" radius.

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After reading so many posts where people struggle to make a cylindrical fretboard (with radius sanding blocks) - I'm surprised others don't blink an eye at attempting a compound radius board. I guess everybody has different skills/specialites? I might give it a try without the routing jig tonight and see how accurately I can sand one by hand.

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I've always been under the impression that if doing it by hand, a compound radius should be made with a -flat- sanding block. I've never tried it, but the theory makes sense:

A compound radius is basically like part of a cross-section of a cone, rather than a part of a cross-section of a cylinder. That means that at ANY given point on the fretboard, there is a difference in the radius. You may be 16" at the end, and 9" at the nut, but you're like 11.234" at the 10th fret, or whatever. I just made that number up.

Point being-- to do it properly, you should be sanding in straight lines, following 'imaginary lines' that are more or less the lines that your strings will follow when you string it up.

Again, I haven't done it myself, but I can't imagine it being easily done using curved radius blocks.

Greg

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Please let us know how this turns out. I recently built a router jig to do this. The degree of precision that is required on a fretboard scared me away from trying to do it all by hand. I have read that someone claims to have developed the skill to create a compound radius using a small plane and does it all by hand that way. I don't have the time to do that nor would I have the time to do one with sanding blocks - that's why I went with the router jig. It still takes a while but it comes out very accurate.

Dave can you show us a picture of your jig? i just recently got a table router and am trying to make a few rigs for it.

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Send me a PM later and I'll try to get you a pic. Unfortunately, the pic won't really explain much. It could be modified to work with a table router but as it is now, the router slides along the top of the jig. There are some pics on the web of other's jigs for this but this one is a bit different. If you decide to build one - be careful and really draw it up and understand the issues. I have seen a couple of jigs that really shouldn't work but probably do as a result of slop in the rotation points and joints.

The main idea is as Greg noted - you need to visualize it as a section of a cone. Rotating a board at one end with a 10" radius and 16" at the other isn't quite enough - the rotation has to pivot at an angle. I'm not going to be able to explain it very well without diagrams - maybe the pic I'll send you later will demonstrate it.

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Hmmm, I can visualize the gradual changes along the fretboard. The centerline height always remains constant while your smaller radius has the most material removed from the sides and then shallows up as you move towards the larger radius. I would begin with a pre-radiused fretboard, that is, the larger radius. Then cut out as many templates as possible between the start and finish radiuses (radii?). I guess you could apply them as a direct ratio to the length of your fretboard. If you have 6 evenly spaced templates between 16" and 9", so...10, 11, 12, 13, 14 and 15" then you divide the length of the fretboard by increments of seven (you will have 7 middle sections). Cut out 6 sections from the fretboard (maybe make slots across the width measuring 1/4") that match each template at each length increment. Remember, the centerline is not touched so your cuts are deepest at the edges and shallow out towards the centerline of the fretboard. Then sand down the middle sections to meet up with each cutout area.

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