Need help with thinning abalone rosette

[Ron Daves]

I'm building a concert Uke. I think I may have thinned the soundboard a bit more than I should have to .078". I want the rosette to be abalone. If I want to use this stuff, I'm going to have to thin it down. If I glue this stuff into the soundboard it's going to be proud and I'm going to have to do a lot of sanding. Doing so much sanding in one spot seems like a recipe for disaster. What do I do to get this stuff properly thinned down?

[Jim McConkey]

An alternative would be to put a ring of extra material around the soundhole on the inside of the soundboard, so that you can route the inlay cavity to the proper depth without loss of strength. I have done a number of reinforcements on complex dulcimer soundholes to keep the delicate parts from snapping off, normally putting the reinforcement layer at 90 degrees to the soundboard grain. This is probably a LOT easier than trying to thin shell!

[Rodger Knox]

+1 to what Jim said, assuming your abalone isn't thicker than the normal 0.04" or 0.06".
Is your abalone thicker than 0.06"?

[Ron Daves]

The abalone is .058"

[Barry Daniels]

You are worrying about something that should not be a problem. Sanding down shell after inlaying is a routine step and it should not thin out the top excessively, if you use the right technique. You need something that will level the shell without taking off wood until the shell is level. Sandpaper loosely held to a block will not work. You need to either glue the sandpaper to a hard block of wood, or use a tool like a short file.

[Mario Proulx]

A file with a wood "handle" glued to one surface is what I use. Any sandpaper, even backed by a hard block, will tend to also remove some of the top's wood, where the file does a nice job of leveling the shell while not removing any wood(if you're careful). Round-over both ends of the file, too, to prevent it gouging your work. This file will soon become one of your most used tools!

Jim's suggestion is also a good idea; it's par for the course in classical guitar construction and won't hurt your uke one bit.

[Rodger Knox]

Although I have not yet used it in that capacity, Mr. Carruth's scraper would probably be a good alternative. A good flat file is the safest alternative, scraping shell can be tricky.

[Ron Daves]

Thanks, guys for all this good info. Got a plan now.

[Jason Rodgers]

I made a sanding disc for my drill press with one of those triangular heads from a sonic multitool thing. It's made of very firm foam with hook and loop on a plastic backer. I mounted this on a bolt and it's very concentric and well balanced, even when spinning 1000+ rpm. The available sanding discs (with dust holes or without) work really well. To level shell in a rosette, I bring the disc down with the spindle lock until it just touches the highest pieces, level, then move the spindle down by a 1/4 turn of the locking nut, repeat. 60 to 80 grit makes quick work, then move to higher grits when I get closer to level. You really have to pay attention to your progress and move up grits at the right time, otherwise you can end up with large grit scratches that are deeper than your desired finish depth. As long as the table is level, it's easy to just hit the rosette and not thin the surrounding top surface. Of course, I do all this with my dust hood that I use with my Wagner for thicknessing.

[Ron Daves]

Thanks, guys for all the help. I decided to go with the reinforcement under the soundhole idea. I've cut a bunch of 1/4" X 3/4" abalone strips to use for the rosette. I plan to inlay short pieces of the ab using CA glue. Then I'll use a file, as suggested to assure that the AB is flush. Comments, please.

[Randy Roberts]

Ron,

One option as to the leveling of the rosette you might consider is to set the abalone a bit deeper in the trough so it does not reach the surface of the top. Then gradually fill over the abalone with your thin CA. This leaves you with just CA to sand level instead of the hard abalone.

A few advantages: It lets you sand the abalone surface down to extremely fine grit, (I'd use micro mesh) resulting in a shinier surface. It prevents your sanding down through the abalone surface into possibly less pleasing abalone when you level the surface, especially with the Ab-Lam type materials, so you end up with the appearance you originally intended. It gives a varying degree of 3_D effect, depending on how deeply set the abalone is placed into the top.

Disadvantages: In previous posts about this, the concern was raised as to the possibility of the CA yellowing with time, but I've so far not seen any sign that this happens. You need to fill the "pool" of CA above the abalone a very small amount at a time or you risk it taking forever to harden. With using more than a few drops at a time you also would risk the exothermic reaction generating too much heat, boiling the CA and getting the opaque white that there is no cure for other than routing it all out and starting over.

[Rodger Knox]

+1 to Randy's technique. I'm 8 years into doing it that way and haven't seen any discoloration.
It is a slightly different look, so it needs to be all one way or the other. You can see it if part of the shell is covered and part is not.

[David King]

The inlay could be thinned safely ahead of time on a disc sander with a backer board and a right-angle T slot table.

[Ron Daves]

Abalone rosette inlaid in test rosette channel.

Rosette.jpg (36.6 KiB) Viewed 13047 times

Today, in an abundance of caution, I made a fake rosette channel and inlaid the abalone. I had several abalone pieces, a little less than an inch square. Using the proper saw, I sliced several of these pieces into 1/4" strips. Next, with a dremel and cutting disk, I parted each piece. Then, with the dremel, I fashioned each small piece, one after the other, to fit into the channel. So, right now, my rosette is inlaid a little proud in the fake channel. Next, I'm going to index my 1/4" router bit so that it cuts a channel in my soundboard almost as deep as the abalone pieces. I'll then glue each piece in with CA glue. Then I'll use a file, as suggested earlier, to level the rosette with the sound board. Oh, yeah, I plan on putting a light coat of shellac around the soundhole to prevent the CA glue from bleeding beyond the rosette perimeter. I've included a picture.

[Ron Daves]

I took Mario's advice and fashioned a handle on a file and used that to level my abalone rosette. Worked like a charm. See pic.

A file with a wood "handle" glued to one surface is what I use. Any sandpaper, even backed by a hard block, will tend to also remove some of the top's wood, where the file does a nice job of leveling the shell while not removing any wood(if you're careful). Round-over both ends of the file, too, to prevent it gouging your work. This file will soon become one of your most used tools!

Jim's suggestion is also a good idea; it's par for the course in classical guitar construction and won't hurt your uke one bit.

[David King]

Most files will have a concave side and a convex side. I like to have the convex side down is it appears you have done here too.