Crawls Backward (When Alarmed)

IconProjects, musings about guitar builds, guitar repairs, vintage tube amplifiers, old radios, travel, home renovation, and other stuff.

Gluing Cocobolo Bridge on the Kay K22 Guitar

Ok, new bridge in hand.  Ready to glue it onto guitar.

I made a goof the first time I put the bridge on.  I had carefully set the bridge up, heated the glue, etc.  But when it was clamped down, it shifted a small amount forward.  Enough to affect the intonation for sure.

Since I had used hide glue, it was easy enough to take it off and start again.

So now I'll go back to the beginning and show the process and the second gluing.

Guitarhenge.  Left on old guitars by druid craftsmen.
I filled the two old saddle height adjustment screws as well as the old string holes with dowels.  As with my old Epiphone which I also filled the holes on, this makes for something looking like Guitarhenge.  

I'm not sure what type of wood these dowels are, but they're fairly soft. Which makes them easy to work with, but the ends look sloppy when you cut them.  Of course they will be trimmed, so it's not a big thing.

I'll be making new string holes to align with the new bridge.

During this process, I also found some divots in the top and wound up making spruce patches to fill them.  You can see how I cut little rectangles it top and made spruce patches to fit them.

It sure looks ugly, but it's reasonably flat.  Not flat like a pancake, but more like a tortilla. Meaning there are some small imperfections, but nothing to lose sleep over.

It's important that the surface is reasonably level since the bridge will be under the stress of string tension.  The more good gluing surface for the bridge, the better.

Now we heat up the hide glue in the heating pot.

Check out my Thermopen.  Super accurate digital thermometer.  I bought it for cooking, but it also doubles as a water temperature checker for hide glue.

Once you have one of these, you find out how inaccurate those cheap Taylor and even Pyrex thermometers are.  Yes, it costs five times as much, but it's ten times more accurate.  In cooking, you can get the precise temperature in say, medium-rare versus medium meat.  Right on the button.

I should have done this the first time.  I drilled the two outer string holes and used my LMI bridge clamp.  I'm really not sold on this clamp's clamp power vs. five or six C-clamps.  But it does hold your bridge in exactly the right place.

Here I am heating up the bottom of the bridge and the top of the guitar where the bridge will go.  I've already run the two alignment screws up through the top.   I like to heat up the mating surfaces to extend the working time of the glue a bit.

Cocobolo has a reputation for being difficult to glue.  Two techniques I read about on the interwebs were: to glue the wood immediately after it was planed, sanded or scraped, and to use acetone or other solvent to clean it.

It's an oily wood.  I scraped it with a small scraper, then wiped it a few times with acetone.  The acetone evaporates very quickly.  You can see the red oil I got off the bridge bottom.  I wiped it a few times until I saw no more oil, then I glued it down.

The LMI clamp on the guitar.  The two screws in the center pass though string holes.  There are knurled heads on them - I just reversed them so it's easy to get the wing nuts on.

Tighten the center nuts down, then the outer screws.  I have a piece of waxed paper and a short caul between the screws and the surface of the bridge.

I got most of the glue squeeze-out up while it was still soft, but there's always some to get later.

Heat it with some hot water and it comes right off.

The bridge is now in place.  It seems very secure, but of course the test will be when I finally string it up.  I think it looks good, though.

 
 
 
 

Post a Comment 0 comments:

Post a Comment