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Trouble radiusing ebony
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Trouble radiusing ebony
Hello everyone,
I’m currently radiusing out a flame ebony fretboard (using 100grit sandpaper), and is giving me some trouble. The radii is 16” and it came perfectly straight along its lenght, but over the width, tough the radius already match the sanding beam, it keep developing along the lenght 2 long areas were it seam to eat more wood than other parts, leaving a gap easyly noticeable under inspection.
At first I thought that since the fretboard was heavyly flamed, there’s some softer wood area along it’s lenght. I tried to address it flattening it with the straight sanding beam but without any success.
Any help? I’ll attach some pic in minutes.
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16 Replies
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Here’s the pic. Consider that there’s an heavy led light so it seem a huge gap, which it isn’t but still worries me for the fretting stage.
Pic taken along 1st, 12th and 24th fret. I used a jig to keep the sanding beam straight so there’s no chanche it was rocking over the fretboard, and thicknes is very consistent along its all lenght.
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can you post some pics of your sanding rig too ?
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Sure, I’m still in the shop, just a couple minutes
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Here you go.
A simple slide, the neck is centered by 2 pins you can see on the bed of the jig. I work from above so the pressure is even.
The only variable I have is, in fact, how I apply the sandpaper to the beam since it’s not the self-adhesive one, I use double sided tape.
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Have you put a straight edge and a reverse radius gauge on the beam? The stewmac beams have more reinforcement it seems. The only other thing springing to mind is that even though you have a great centerline maintaining jig, it’s still possible to put downforce in evenly. it might be good to mount some handles onto the beam to even the pressure.
edit : are you generating heat when you are sanding?
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In fact I believe to have never checked the surface of the beam with a reverse radius gauge, but with the straight edge is spot on. I had this from a many years now. Will do tomorrow another check. (Good idea on the handle too).
About the heat, I can say yes, cause I can feel it over the fretboard while roughing in or while vacuuming the beam to clean the dust. Must say I’m using aggresive grit right now. But I am at the point where I should start using finer grit to finalize the fretboard, tough I still have plenty of thickness to work on if needed.
Tough I know ebony may very a lot in color and is not naturally total black, I believed for a while that those brownish spot were sapwood. Ence why it tend to be a little softer along its lenght on those point, maybe. But that’s just me overthinking, probably.
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Is the neck hold down putting any tension into the neck ?
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Nope, I put 3 stripe of double sided tape (heel, center, nut) just to be sure to keep it flush with the bed of the jig, other than that it could be held by the two pins themself alone.
Consider I do the radiusing process before shaping the back, just to be sure the neck to be itself naturally straight. The truss is completely loose and the neck is dead flat on its lenght.
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My prime guesses are heat or funk in the radius block. If you are using epoxy to glue the FB on, you might switch up to hide glue. It has better resiliency to heat unless you pony up for hi-temp epoxy. Another way to reduce heat on a budget would to get one of those jigs to hog the radius off with a router. If you are trying to go from square to radius with the block alone, that makes me sad just thinking about it.
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It’s glued with standard Titebond, in terms of glue I only used Fish-glue, which I like/dislike at the same time and polyurethane glue, which totally don’t like.
About the radiusing process, yes I start from the squadred fretboard, with a 100grit sandpaper I usually take 10min to reach the radius (I only use 16” on my builds) and other 15 to finalize it till the 400-600 grit. Not a big deal but I thought about buying that jig too, not for the fatigue itself but mostly cause it’s an boring process.
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Finally managed to finalize the radiusing process, but I’m goin to replace the sanding beam. Along the width it is still ok, but along the lenght it developed an unnoticeable up-bow that worries me a lot. Stew-Mac sanding beam incoming, I’ll use this one as a caul for repair-gluing.
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As weird as some things goes in life, my most difficult radiusing process ended up in being the most easy fret job I have ever done. In fact the frets are so evenly seated with a tollerance of less than 0.05mm that the fretboard does not need any dressing. Hope this came more often!
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Also, did you see the jig I 3d printed for maintaining centerline while sanding ? I think it has some advantages over your rig.
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Which one, sorry? My internet connection suck today
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That look very clever in fact
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