Erlewine Cuts Curved Truss Rod Slot With Table Saw

The Luthier Bench Knowledge Base

How can a table saw cut a curve? Dan Erlewine has a neat tip and a jig you can make in your shop. The result is a precisely curved truss rod channel just like the one in an original Gibson neck.

Transcript

00:00Today, I'm installing a truss rod access hole in this Gibson-style neck.

00:14It's as easy as that, and it didn't take long, did it?

00:18Something I'd like to show you is my slot in here is curved.

00:23It's not a straight flat-bottom slot.

00:25I cut it on a curve.

00:27I can show you that exact curve on this cut-in-half Gibson neck.

00:31The reason you want a curved truss rod slot is because when the neck pulls up, which they

00:35do, you string up a guitar neck and it pulls up over the years and you get high action,

00:40you tighten that curved rod and it comes back down again.

00:43The first thing we'll need for making a curved channel are the measurements off this Gibson

00:48curve.

00:49This little point sticking into that glue line, that's where I measured from.

00:53That's the joint between the mahogany and the rosewood board.

00:56The deepest part was at the seventh fret.

00:59As I went down, it got shallower, and that gave me the basic depths all along the curve,

01:04which I was able to copy.

01:06I took all these measurements and I transferred them to a stick, connected the dots like that.

01:13I sawed this out and got my curve.

01:17Now this is just a template for making a jig to go on my table saw.

01:22A table saw is made for cutting straight lines, and if you cut a truss rod channel like this,

01:26it will be straight, not curved.

01:29But if you add a curved piece of wood to the table saw, you'd get this jig.

01:35The secret is to put a shim on the beginning and the end of your neck block so it will

01:39raise up as it comes onto the curve and cut shallower, and as it passes over the blade

01:45onto the other side, it's cutting the deepest part of your channel.

01:50Then as the other end with its shim comes over the curve, it starts to raise it back

01:54out again, and the result is a curved channel.

01:58So let's make that jig.

02:01This is a piece of 2x4 Douglas fir, and I have my template, curved side down, flat side

02:07right flush with that board, and I'm just going to draw that out.

02:13This is my arc.

02:17And I keep moving the arc along.

02:22Now there's a long curve, but cut off on the bandsaw.

02:37Okay, here's my long curved board.

02:40I'm going to pull out this throat and fasten it to the bottom of the board.

02:46That's how I mounted it.

02:49Now I'm going to cut right up through it with the saw blade.

03:03The next step is to put little shims at each end that raise it up off the curve as you

03:08cut.

03:09I'm going to superglue these shims down.

03:12They pop right off with a chisel.

03:15Set that there.

03:17Let that dry a second, and I can make a cut.

03:21Wish me luck.

03:31The teeth aren't that wide, so I'll make three cuts, one right on the center, one I'll move

03:36the fence over a little bit, it won't take much, like a 30 second, then I'll move it

03:41back the other side, and I'll get a 3-16ths slot.

03:56That's it.

04:01So, there we have it.

04:04We have a professional slot cut right through this mahogany blank for a Gibson style 3-16ths

04:11diameter truss rod, and it's got a curved bottom, and it's very cool.

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