Crawls Backward (When Alarmed)

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Making a Cocobolo Bridge for the Kay K22 Guitar

Now that we have a new bridge plate, I think it's time we make a new bridge to go with it.

You might be surprised to read I'm going to make one out of cocobolo.

On the left you see a cocobolo blank, and on the right the bridge that came with the guitar - a replacement for the original.  In the middle is a pine blank I made to get the contour correct.

You can see that the 'original' bridge had the string holes placed a bit too far away from the slot.  Too far in my opinion.  The saddle slot is also very shallow.  I'm going to make the same shape, but move the holes up some and make a deeper slot.

I traced the shape onto the blank, and cut close to the mark with a jigsaw.  One of these days, I'll have a bandsaw to do this.  Someday.

Then I stuck the blank onto the pattern and used the robosander to sand the contour.

The robosander is an amazing device that works with your drill press.  The bottom is a guide that runs against your pattern, while the top is a sanding drum that sands the wood down the the same contour as the pattern.

Here's the blank after sanding.  You get an exact clone of the pattern!

For someone like me, who is a hack at filing and sanding a curve, this is gold.  Gold, Toy Making Dad, gold.

Next we measure for the saddle slot.

I use this Saddlematic device from Stew-Mac.  The pins in the aluminum block are the bass and treble ends - compensated - for the front edge of your slot.  They're sharp so they make little divots in the bridge.

Then you draw a line and use that as your guide to rout the slot.

This is a simple device you could probably homebrew, but it's inexpensive enough that making your own isn't worth it, unless you're a machinist.

The tape is just to hold the allen adjustment wrench on so I don't lose it.

Then over to my homebrew slotting jig.  Again, another Stew-Mac tool - their 'Precision Routing Base.'  It's a decent tool for this job, although some folks on the interwebs don't like it.

My real need for improvement here is my jig.  I built it from the plans at Ultimate Guitar (I think) and it needs some improvement.  Mainly the wings at the ends don't hold the workpiece firmly enough.  I tend to get an uneven rout, and I got some tear-out on this one from the piece shifting.

The concept is good, but it's too clunky.  I have some ideas for my version 2 of this jig.

Back to robosander!

Here I used the original bridge as the pattern - it's on the bottom, running against the guide.  The new bridge is on the top.

Cocobolo makes a ton of dust.  It was going everywhere, so I eventually put the end of my vacuum hose on the drill press table and collected it that way.  But not before I captured this action shot.

If you use cocobolo, be aware that some people are allergic to the dust.  I am not.  The dust smells amazing - it's a dark smoky smell sort of like chipotle peppers!  That's the only way I can describe it.  And since it mainly comes from Mexico, it's appropriate.

Next time I will use gloves.  My hands still smell of the stuff.  Fun for a while but not good in the long term.

Here's the rough contoured bridge.

I used 60 grit on the sander - you can see some marks that will come out as we progress.  And you can see some of the goofy spots in the rout.  I actually filled them later with cocobolo dust and CA since they were really bugging me.

Love that grain.  I have some really spectacular pieces I'll use in the future.

Next, I drilled the string holes.  I decided to follow the slant of the rout this time.

And the next-to-last touch is chamfering the holes with a chamfer bit and my trusty English-made Stanley hand drill.

The finished bridge.

I sanded it all the way up to 12000 grit paper, then polished it with EEE Ultra Shine and Shellawax.  It has a nice gloss - hard to see in the pictures.

The Ultra Shine really highlights the grain.  The more I polished, the deeper the grain looked.

Really nice grain along the back.  Too bad this is going on an old junky guitar.







 
 
 
 

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