ca. 1936 Regal-made Dobro Tenor Guitar Restoration, Pt. 3: Neck Reset

With the neck removed, we can start the process of resetting it.

You may recall I took some measurements before I took the neck off. There is a formula to determine how much to remove from the neck heel to have the neck angle be correct.

This neck had such a bad angle that my calculation was to remove about .09 of an inch - almost a tenth of an inch (!) off the bottom. Because of the difficulty in getting an exact read on the bridge due to the resonator, I decided to be conservative and mark about .07 to remove. I could remove more if needed.

You can see how I laid this mark out on the heel. I used an X-acto knife to scribe a line. The bottom is .07 in. from the edge of the heel, and the line progressively goes up to zero at the top of the heel.

The line is marked on both sides.

You should be able to visualize what removing this material will do to the angle (or "set") of the neck - it will pitch it backward, resulting in lower, correct string height.

In the past, I've used a paint stick with sandpaper attached as the tool to take the material off. But I realized the stick tends to flex, and we need to remove that edge in a straight line.

So I cut a piece of scrap poplar left over from my workbench drawer slides and turned it into a hardwood sanding block. I used spray adhesive to attach a strip of sandpaper - 120 grit.

At this point, I've removed quite a bit of material from the 'cheeks' of the heel. This means a ridge will develop at the part of the heel under the dovetail. That can be removed and the heel undercut with a chisel.

All that needs to contact the body of the guitar is the edge of the heel, so an undercut won't affect the neck joint - in fact, removing material with a chisel will make for less material to sand off.

I do undercuts also from the side edges down toward the sides of the dovetail as well. You can see how that part of the heel angles down.

As an aside, I believe you would call this part of the dovetail the 'pin.'

Getting close at this point. I still need to take some of the lumpy part out of the bottom.

This is the trickiest part of the whole process. The line needs to be as straight as possible, and even on both sides.

Note the dovetail - it's pretty rough. That's the way it came out of the guitar.

We're about ready to do a test fit.

That big block is my sanding stick - the focal length of the lens makes it look huge!

Note how much I've taken off, and note that downward angle/undercut I made on the sides and bottom around the dovetail.

This is about perfect.

And this is misleading - I did quite a few test fits as I got closer; I didn't just magically remove the right amount and it worked!

What a difference. The straightedge hits right at the mark I was aiming for.

Previously, it would have landed somewhere down on the aluminum bridge.

Since the angle has been changed, the fit of the dovetail is loose now. So we'll shim it up.

Note I sanded off some of the rough bits of the dovetail - I couldn't stand the sight of it.

I made two shims from maple bridge plate stock. They're unattached and untrimmed at this point. They'll tighten up the fit of the dovetail.

Here the shims are glued and clamped up. I have two cauls that fit the angle of the dovetail and have square outside edges so they clamp easily.

I put waxed paper between the cauls and the shims - note the squeeze out. I don't want to glue the cauls to the neck - just the shims.

After the shims are glued on, we use a piece of carbon paper wrapped around the dovetail to help shave the shims down.

With the paper on, press the neck down.

It won't go far down with the shims first installed, since they're so thick they'll only let the neck go down about halfway.

The carbon paper will leave marks on the shims where they contact the body part of the joint.

Here's the body side...a bit rough looking.

As an aside, I believe in technical woodworking terms, this is a 'socket.'

Note the spot where I drilled into the joint. Close but not exactly perfect. Still got the neck off easily.

Then we shave off the areas that got marked, using a scraper.

Then repeat the same process - carbon paper, fit, scrape, until the pin seats into the socket. (If those are the correct terms).

Finally the joint is reasonably tight. I use not only the tightness of the joint, but also the corner where the fretboard meets the guitar top as the final judge of a good fit.

At this point, check the side-to-side angle of the neck and the alignment in relation to the bridge.

Last step is to use sandpaper strips between the body and the neck to adjust the contour of the heel to match the body.

I bought a roll of canvas-backed paper from Stew-Mac for this job. Regular paper-backed sandpaper tends to tear. This stuff works great.

Put the strip in place, hold the neck to the body, and pull the paper toward the bottom of the guitar. I do a few passes on one side, and the same number on the other so that both sides are even.

I'm going to replace the tuners, so I take them off. The owner and I think these are not original, and he's splurged for some nice Five Star geared banjo style tuners.

Since I need to enlarge the tuner holes for the new tuners, I figure it's easier to do that now while the neck is still off the guitar.

Enlarging tuner holes is one of those tasks that seems easy, but can be tricky. I've used sandpaper attached to dowels (good if you only need something like one millimeter removed), files (good if you don't care if the hole winds up less than perfectly round), reamers (hard to avoid a cone-shaped taper in the hole).

So I searched on the interwebs, knowing the answer was there. Sure enough, I found a YouTube video outlining this simple but effective method.

Emulating the video, I made up a simple jig with dowels the diameter of the old tuner holes (I think they were 1/4 inch) stuck in some holes.

The dowels protrude about half the distance of the depth of the headstock. I'll put a tuner hole over a dowel, drill down halfway, then flip it over and drill the other half.

Here it is in action. I used a Forster bit on the drill press, and it worked well. Ideally, you'd have two dowel sizes - one the original size and one for the new size. Using the same size for both sides of the hole meant I had to be careful lining up the bit on the second side, but it worked well.

Better than trying to use a larger bit freehand, where the neck will want to spin freely as the bit enters. The dowels help keep the neck steady.

Note I also drilled out the old screw holes for new dowels (1/8 inch) to fill them. I can't stand seeing ragged old screw holes left on headstocks. Careless, lazy work if you ask me.

Almost there!

Line up some clamps and cauls to fit the neck back on.

I strongly suggest doing a dry run with your clamps - get them adjusted closely in advance. Especially if you're using hide glue, you have a limited open time, and having everything ready to go is a huge help.

Doing a test also makes sure you are aware of any problems. Nothing like having applied glue to a part and realize there's an issue. Been there.

Did I mention problems?

While I was getting the neck ready, the fingerboard separated from the neck at the top. Glad it happened now. I'll re-glue it first before I do the neck.

It's a good idea to scrape the top of the body where the fingerboard extension will be glued on. A clean surface will ensure a good glue joint.

Also do this on the underside of the extension.

Note I've taped up the area around the extension - to avoid damaging it and to keep glue squeeze-out off the top.

Then I heat up a fresh batch of hide glue in my special luthier's hot pot. I've got some glue in a syringe also to squirt into that fingerboard joint.

Here's the fingerboard glued up and clamped. Note the squeeze-out- I haven't cleaned it off at this point.

Note also the neck caul - I made this a while back for just this sort of job. Real simple - just a wood scrap (pine) cut on a bandsaw and lined with cork.

It might seem like a pain to make these cauls, but once they're done, you can just grab them and use them.

I find I actually enjoying making them.

And finally glue up the neck.

The caul you see on the front has about a 12 inch radius with fret 'slots' cut into it.

Under the neck heel there's a small block topped with cork to protect it from the clamp.

Next time - re-stain the neck, put on pearl dots, and refret.