Truss Rod Slot Jig and Slot Routing on the Vintage Kay Guitar

I'm now just about ready to rout the Kay neck in order to put a truss rod in it.  So far the fingerboard removal and the neck removal have been straightforward and I was confident there wouldn't be major problems.

But this is a whole new world.  (Cue Antonin Dvorak's Symphony No. 9 here).

I have a 'Hot Rod' double action truss rod from Stew-Mac. I also have their special router bit to rout the channel.  I'm thought this through for some time and it's getting near to The Moment of Truth.

I had to make a jig to hold the neck.  A lot of folks on the TDPRI forums make a sled wherein the neck lies in a channel and the router passes over it.  For a Telecaster neck, it makes a lot of sense, since the neck is so shallow.  But I have an acoustic neck with a deep heel.

So I found a couple videos on the interwebs where folks used a jig with the neck clamped underneath.  That seemed to be a better idea to me.

So I hacked out a rectangular piece of 1/2 inch (12mm) plywood.  The guide on my trusty Ridgid trim router is exactly 3 inches wide, so I just measured around that - the center channel is 3 inches, I allowed 1.5 inches each of  the channel guides, and another 2 inches on either side for legs.

The picture above is where I glued pieces of 1x2s on what will be the top of the jig to make the channel.  I had sanded the top up to 600 grit paper, and did the same on the inward facing parts of the channel 'walls.'  I figured smooth would be good.

Here's the router bit.  It's not cheap, but I wanted to be as accurate as possible.  Some of the reviewers on the Stew-Mac site mention how sharp it is.  So sharp that they put a waxy cover on it.

It's sharp.  I didn't touch it.  I could just tell.

Then I routed a slot the exact length of the rod - 14 1/4 inches - into the board using the new channel as a guide.

Then I put two Destaco toggle clamps along the slot.  They're the model 207UL - they have a longer arm.  I bought the spindles too (the vertical screw things), but I didn't need them.  I'm sure I will at some point.

You see I also put legs on the thing.

Mark a center line on the neck.  I also put drafting tape at each point where the slot should end.  The slot on the jig is the same length as the rod, but I needed a reference on the bottom so I could align the neck on the jig properly.

The neck clamped into the jig.  Remember this is the bottom.  The rout will be done from the other side.

A couple of notes.  The blue arrows show the tape.  You can also see where I made a line across the board indicating the end of the slot.  This just helped get it close to being lined up while clamping it down.

The green arrows show some cauls I made up to go under the clamps.  One side is a radius with a piece of cork glued on it - that's the neck side.

Since the neck is thicker in diameter near the heel, and thinner near the nut, I sanded the blocks to different thicknesses to fit tightly between the neck and the clamp.

The clamps are rated at about 500 pounds of force, so the neck will not move at all in the jig.

Here's the neck centerline going down the center of the slot in the jig.

I found that with just one clamp about halfway locked down, I could slide the neck against the caul enough to get it positioned exactly both end-to-end and crosswise in the slot so it was perfectly aligned.  Then I clamped it down.

Clamp the jig down to the Workmate.

Deep breath, then fire up the router.  I set the depth to go about halfway into the neck.  My router doesn't have a plunge base on it, so I had drilled a 7/16 deep hole at the heel end of the slot.  Then I could drop the router right in, and then start it up.

This is after pass one.  Love that vintage mahogany dust!  The jig worked perfectly.  The router stayed right on the line, and stopped at the end where it should. 

I made two passes and I was pretty confident I had the right depth.  I put one end of the rod in, and it looked like it was not quite deep enough, so I ran it a third time to shave about a 64th of an inch off.

Here's the newly routed neck.  I'm very pleased with it!  I was very careful and patient and it paid off.

You can see the rod on the bench behind the neck.  It has an adjustment nut on the end as you can see.

Now I need to drill an access hole through the top of the dovetail so that nut will pass through it.  The slot for the rod is cut to the length of the rod but not the adjustment.  This will be clearer in the next post.

I'm going to have a modern, double action truss rod on my vintage Kay!  Crazy!