In our last installment, I did the maths for the neck reset and found I needed to remove .040 inches from the neck heel in order to have the correct neck angle.
I need to transfer that measurement to the bottom of the heel.
Removing this material will tilt the neck back ever so slightly, changing its angle.
The blue arrow in the picture shows the marking I made. In the past, I've used pencil to mark this (not dark enough and rubs off easily), tape (not accurate enough and can shift) and markers (too thick and hard to control).
This time I got brave and used a scribe to draw the lines. I made the lines just a tad less than what I needed, figuring that they'd be erased as I removed material.
One side is 60 grit and the other side is 100 or 120, whatever I have on hand.
This cuts a lot slower and I find it to be more accurate than using a chisel. Just sand away to follow the scribed line.
(And we'll fine tune that fit too).
To see what I mean, note how the straightedge is lying just on the top of the bridge.
That's a correct neck set.
The first is on the fingerboard. You can see this crack on the fingerboard extension - I have it opened up here with an X-Acto knife.
The whole board seems to have this sort of separation joint on both sides. It should be solid ebony, but it looks like it split or was opened up at some point. Some of the edges are quite rough looking. (If you look closely at some of the pictures, you'll see what I mean. The edge of the fingerboard is not quite right).
Sven of Argapa Ukuleles asked me about putting a rod in the neck, and I too had thought about putting a truss rod, or a carbon rod in the neck to correct the upbow it has. But after I saw these splits, I decided it wouldn't be a good idea to mess with trying to get the fingerboard off.
I'm not sure what happened to the fingerboard, but I'd guess it's been worked on in the past - and probably refretted. Martin didn't use T-frets until 1934, three years after this guitar was made, so it should have bar frets. Meaning this guitar has most likely been refretted. And I'd guess the board suffered some damage during that process.
At any rate, it's easy enough to fix that crack.
I'll need some to reattach the neck anyway, so I can use it to fix this crack - and others I found too.
I get some thinned glue into a syringe. This one has a 0.9mm tip and regular thickness glue won't pass through it, so I thin it about 50 percent.
And then we inject the glue into the crack.
Of course, we have about a 60 second or so open time with this glue. But we can make it longer by heating the pieces that will be joined - note the heat gun lying on the bench. I get the wood warm to the touch and that gives a longer working time.
The glue is heated to 145 degrees F. It will begin to gel at 90 or so.
I'm using a caul wrapped in waxed paper, so any excess glue won't get stuck on the caul.
Note the waxed paper inside the guitar, because...
Sorry for the bad picture - working quickly, grab camera for quick shot and it didn't autofocus.
I use manual focus on a lot of my closeup shots but didn't have time on this one.
But you get the idea. It's glue. Squirted into a crack.
Next time - shimming the dovetail and making a caul for heat straightening the neck.
All posts in the 1931 Martin 0-18T Restoration Project:
- 1931 Martin 0-18T Guitar Restoration and Repair, Pt. 1
- Neck Removal on 1931 Martin 0-18T Guitar: Restoration and Repair, Pt. 2
- Trimming the Neck Heel for Reset: 1931 Martin 0-18T Restoration and Repair, Pt. 3 - This page.
- Shimming Guitar Neck Dovetail and Finish Chip Repair: 1931 Martin 0-18T Restoration and Repair, Pt. 4
- Caul for Heat-straightening Guitar Neck: 1931 Martin 0-18T Restoration and Repair, Pt. 5
- Reparing Acoustic Body Cracks: 1931 Martin 0-18T Restoration and Repair, Pt. 6
- Making a Tortoloid Pickguard: 1931 Martin 0-18T Restoration and Repair, Pt. 7
- Heat Straightening Bowed Guitar Neck: 1931 Martin 0-18T Restoration and Repair, Pt. 8
- Fret Marker Installation and Filling Fingerboard Chips: 1931 Martin 0-18T Restoration and Repair, Pt. 9
- Compression Fretting to Correct Upbow: 1931 Martin 0-18T Restoration and Repair, Pt. 10
- Completed 1931 Martin 0-18T: Restoration and Repair, Pt. 11