Crossover Comb Restoration

You can paint the surface of the comb with a sharpie or, better, a crayon.

Rub the painted surface on the backside of the sandpaper and the high spots will be where the paint rubs off. This gives you an idea where the problem areas are.

You can also paint the surface before sanding. When all the paint comes off, the surface is flat.

Got a Crossover in that really leaked. I took the comb out and it looked much like yours. Very nasty. This is after a bit of sanding just to work on it. That groove had to have come from the factory like that as there was lumps of sealer in the grooves. This harp got a custom comb. I have filled the grooves on this comb and put some MB reed plates on it to see how it will hold up with the wood filler. 

I have really enjoyed the harp tech series. Keep up the good work.

.....Mike

Hi Guys,

Comments for both Kinya and Winslow, but first I’d like to thank both of you for all you contribute here on bluesharmonica.com, I’ve learned much from you.

Kinya, I used to make and repair/service high end wooden Flutes and Recorders, so I feel your pain with regards to the nastiness that lurks inside of used harps - I’ve seen plenty of Recordacoccus in my day, lol.

Regarding the fishing weight, I love the idea! That said, my own observation is that it takes less than 3lbs to bend a harmonica comb, so I can see where this could cause problems getting a warped comb truly flat, since the weight will flatten the comb to some extent when placed on the comb before you even begin sanding, then will spring back to its warped state once sanded “flat”. As a general woodworking principle, one would not apply enough pressure to bend the piece being sanded, unless one likes to go in circles..... lame orbital sander pun there. I assume you are checking the comb on a truly flat surface after sanding, so how are you avoiding the bending issue while the comb is weighted?

It also drives the machinist in me nuts that the fishing weight doesn’t evenly apply the weight to the entire surface of the (flexible) comb, because this can potentially magnify the bending problem, but I realize we aren’t lapping space shuttle parts here, lol. Kinya, have you ever considered having a machinist make you some blanks out of bar stock that exactly conform to the outline of each type of comb you commonly need to flat sand? This would solve the bending problem, because the bar stock could be relatively light, and would also solve the problem of even weight distribution over the surface of the comb. Would serve double duty as a reverence flat surface for testing flatness of the comb before, during and after sanding, as the bar stock would be milled perfectly flat all around. Sadly, I no longer have access to machine tools, or I’d make us both a few blanks for various combs. Perhaps you could convince a machinist you know to make you one to try? (Greg H, possibly?)  

One could obviously also use an aluminum, brass or demonstrably flat corian or acrylic comb of the same type on top of the comb being sanded, as a less perfect but more easily available alternative.

I know, I know, the fishing weight is cheap, easy, and available. And if you are getting truly flat combs using the fishing weight, no reason to change and it could be a great idea for others as well. Just not sure how you’re avoiding the bending issues. 

Winslow, excellent idea regarding marking the surface to be sanded, this a very helpful technique used by both machinists and woodworkers. That said, paint, crayon and sharpie are all bad choices for wood, as all will go well below the surface of the wood, forcing you to sand far more material off than is necessary desireable. The paint and sharpie will wick their way into any porous surface, like unfinished wood and bamboo, and the paint will also clog your sandpaper, plus also potentially redeposit some of that paint back on/into the freshly sanded surface. Crayon is even worse as it is waxy and will get driven into the pores of the wood, and what crayon does comes off into the sandpaper will clog your sandpaper even worse than paint.

Pencil is the way to go and is what woodworkers use because, with a light touch, the graphite stays essentially on the surface of the wood, and it will not clog your sandpaper or redeposit, saving you sanding time, money, and hassle.  

Also, the pencil shading doesn’t need to be solid, just make closesly spaced lines on every part to be sanded, you can do this with a single continuous, closely spaced wavy line on each place that needs to be marked.

Sharpie can be an excellent choice for fully sealed combs that need to be sanded after the sealant is applied, provided the poly or whatever has fully cured. 

OK, that’s about enough outta me! 

Loren

Here is the result of the grand canyon comb. A harp Richter tuned. I use it for chasing foxes so it gets a fair amout of slobber. That shoud test out the "fix". I forgot to take a picture of the repaired comb.