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Exasperatedly sanding cocobolo

PostPosted: Sun Nov 04, 2018 5:47 pm
by Peter Wilcox
I've had trouble sanding (shaping and radiusing) a cocobolo fret board. I made one a couple of years ago and don't remember so much trouble, but maybe I did it by hand instead of machines, so the paper didn't load up as fast.

Basically it rapidly loads the sandpaper, making it look like I was sanding a wax candle. Neither a rubber cleaning stick, a knife nor a screwdriver is very helpful in cleaning it out, and it quickly ruins the sandpaper - thickness sander, belt sander, disc sander. I didn't try acetone or lacquer thinner as I didn't think they would penetrate deeply enough to wash out the oils.

The only thing that seemed to help, taking longer to load, aside from sanding by hand, was using the coarsest grit possible, which in my case was 80. Any tips would be appreciated, as I have 8 more fret board blanks I may get around to using some day.

Re: Exasperatedly sanding cocobolo

PostPosted: Mon Nov 05, 2018 2:14 pm
by Rick Milliken
Would a scraper cut to the right radius get you there? Final polish with a scotch brite pad? That's what I've done on violin fingerboards, but never tried specifically on cocobolo.

Re: Exasperatedly sanding cocobolo

PostPosted: Mon Nov 05, 2018 2:19 pm
by Mario Proulx
Hand plane to the rough radius, then sand to final radius with nothing finer than 40 grit. 36 is even better. The progress to the final grit that you desire.


Some cocobolo will sand nicely without gumming, others will frustrate to no end... ;)

Re: Exasperatedly sanding cocobolo

PostPosted: Mon Nov 05, 2018 5:23 pm
by David King
Any heat you generate will melt the wood resins and bind them to the sandpaper instantly. I hear of people cleaning the residue off with oven cleaner but you might have luck on sealed belts running them through your dishwasher or just soaking them in hot soapy water overnight. Stearated sandpaper holds up a little longer. The mesh clothes like abralon hold up the best.

Re: Exasperatedly sanding cocobolo

PostPosted: Mon Nov 05, 2018 6:19 pm
by Mark Fogleman
Although it sounds counter-intuitive, try turning down the the suction on your shop vac if you have one connected to your power hand sander. Full suction can reduce the airflow by clamping the sanding pad tight against your workpiece, increasing heat and reducing the particle capture. I put a "y" fitting in line with the hose with a cap on one of the arms of the "y" and drilled a 1/2" into the cap. Then cover the hole with blue masking tape when I need full and remove it when it needs to be reduced.

Also, try soaking the goobered abrasive in a strong Simple Green and water solution over night and scrub with a brass bristle suede leather brush to get it off. It's the best solution for this problem I've found.

Re: Exasperatedly sanding cocobolo

PostPosted: Tue Nov 06, 2018 8:24 pm
by Peter Wilcox
Thanks for the suggestions, folks. Maybe I just had a buttery piece of wood. If the problem persists with the next one, I think planing is the way to go for a rough radius, then sand by hand. I don't want to spend any of my remaining time washing sandpaper. :x

Re: Exasperatedly sanding cocobolo

PostPosted: Wed Nov 07, 2018 5:01 pm
by Gordon Bellerose
Peter, it sounds like it may be time to start routing your fret board radii.

You still have to sand to finish, but the majority of the work is done by the router bit.

Re: Exasperatedly sanding cocobolo

PostPosted: Thu Nov 08, 2018 7:59 pm
by Clay Schaeffer
/www.ebay.com/itm/16-Radius-Guitar-Finger-Board-Radius-Router-Bit-1-2-Shank-Yonico-13006/282450252639?epid=3020162607&hash=item41c358d35f:g:9r0AAOSwvtFZ0nNN:sc:USPSFirstClass!21904!US!-1:rk:1:pf:0

I bought one of these router bits, but haven't used it yet. With the right jigging and multiple passes (taking small bites) I think it might work o.k. Being a tall narrow bit hogging off too much wood might leave a rough cut.

Re: Exasperatedly sanding cocobolo

PostPosted: Sat Nov 10, 2018 6:26 pm
by Peter Wilcox
That bit was discussed a little in this thread:

viewtopic.php?f=4&t=5593&start=20

It looks a little scary, but thanks for the suggestion. I think I may make a simple jig for radiusing, just roughing it out, if I ever get around to it.

Re: Exasperatedly sanding cocobolo

PostPosted: Sun Nov 11, 2018 2:06 pm
by Gordon Bellerose
Hey Peter.
I used this plan, which has been posted a few times on this forum, to make my radiusing jig.

I used 2 inch pvc pipe for each side. I drilled holes in the top of them big enough for the screw head and screw driver to go through. That way, the screws that hold it down wouldn't deform it, and they would be out of the way when using the jig.

It's pretty simple, and works well.
You do have to be careful when making the router "cradle", to get an accurate radius.

One of the advantages is that you can make other cradles for different radii.

Radius Router Shaping Jig.jpg

Re: Exasperatedly sanding cocobolo

PostPosted: Sun Nov 11, 2018 4:28 pm
by Peter Wilcox
Thanks Gordon, that looks like the kind of jig I can Mickey Mouse together out of junk lying around without going over my daily allotment of sloth.

Re: Exasperatedly sanding cocobolo

PostPosted: Mon Nov 12, 2018 12:28 pm
by Clay Schaeffer
I tried out the bit I bought off of ebay (Yonico 16 inch radius). I didn't do a lit of jigging, just used what I had on hand. I had reasonably good luck with it and got a surface that with a little bit 0f scraping (to remove a small ridge I intentionally left) and sanding I think will be quite usable.
My setup was just the simple jig I use for routing neck blanks and as a fence for the "router table" that is just a router base mounted to the auxiliary table of the table saw. The untapered blank was hot melt glued to a scrap of particle board.

Re: Exasperatedly sanding cocobolo

PostPosted: Mon Nov 12, 2018 12:34 pm
by Clay Schaeffer
I made several passes moving the fence back a little bit each time to avoid having the bit grab the work. After routing the first side I "unglued" the hot melt from the particle board using alcohol. and then removed it from the blank with alcohol and an old dull chisel

Re: Exasperatedly sanding cocobolo

PostPosted: Mon Nov 12, 2018 12:44 pm
by Clay Schaeffer
I reglued the blank to the particle board scrap and ran the other side. I instead of moving the fence back each time I left it in the "final - finished" position and just did light passes not allowing the bit to dig too deep. Climb cutting may have been a good method for doing this, but I did O.K. routing in the normal fashion. I have a fair amount of experience using routers and am comfortable (but try not to be _too_comfortable) using them. The cutter is slightly proud of the bearing so I set the bit so it would leave a little bit (1/16th in.) in the center of the blank for the bearing to ride on.

Re: Exasperatedly sanding cocobolo

PostPosted: Mon Nov 12, 2018 12:52 pm
by Clay Schaeffer
With a little bit of scraping with a card scraper to remove the ridge I intentionally left and some light sanding I got a surface I think will be suitable for tapering and final finishing similar to what is commercially available. So overall I am happy with the performance of this bit. There are some things I need to fine tune, but that is more about my setup, and less about the tool.

Re: Exasperatedly sanding cocobolo

PostPosted: Mon Nov 12, 2018 4:44 pm
by Peter Wilcox
Thanks Clay - that looks like a reasonable method, as long as there's no tearout or grabbing. I guess you take really small bites. I don't have a router table, but you say you've used your table saw base. I've been meaning to do this, since I never use the table saw any more - maybe this will push me some.

Re: Exasperatedly sanding cocobolo

PostPosted: Mon Nov 12, 2018 8:01 pm
by Clay Schaeffer
Hi Peter,
The router base is mounted under the 3/4 inch plywood extension table of my table saw, so I still have full use of the tablesaw. I use my table saw quite a lot as a saw, but when not using it that way it provides a work surface for assembly, and when covered with cardboard or a plastic tarp, finishing.
When routing I just kept light pressure against the bit similar to what I do when using a router hand held (but I would not try this bit hand held). I make several passes and only make a final "clean up" pass when I feel the bulk of the material has been removed.The final pass I try to do in one continuous smooth motion, similar to the final pass you make across a jointer. I like to leave the board a little longer than necessary for the little "burbles" that happen when starting and stopping a rout. For a production shop this way of milling wood might not be efficient, but for doing a few fret boards at a time doesn't take too long - much quicker and less dusty than sanding. The bit is probably long enough to do a 4 inch width. The board I used was 3" wide, so part of the cutting edge stayed below the table.
Yonico makes a number of different radiuses to choose from, and will even sell you a set. I bought a 16"radius but they also make 7 1/4, 8 1/2, 9 1/2 ,10, 12 inch radiuses. They sell the set of 6 for $99.