Harmony H1457 archtop guitar repair

This is a Harmony H1457 Monterey archtop guitar. It's similar to the H1456 model but in a natural finish. It's got a replacement bridge and tuners but otherwise appears original. I'm not sure the age but I'd guess 60's due to the adjustable trussrod. It is naturally missing the pickguard and trussrod cover. Like all USA-made Harmony's it has a solid top, spruce in this case, which is coming apart at the seams.

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The gap at the heel makes this an obvious candidate for a neck reset. The action is really bad. I didn't grab a picture of it but it's nowhere near playable.

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The frets are a bit worn but not really screaming for a reset. But the inlays are screaming for a fretboard planing.

You can see the finish on the top is in pretty bad shape. There are several places where the finish has been scraped away and bare wood is exposed. Also there's a variety of dings and stains. And there's cracks, cracks, cracks.

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This is the most obvious of the structural damage. The bass-side F-hole is being held together mainly by the cloth back underneath. Completely unstable.

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Here is a more interesting crack on the bass side of the waist. This is a deep groove. I don't understand how this could be caused. In any case, it's very stable.

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There's also a minor split in the top behind the bridge which appears stable.

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In the image above you can see every crack I identified on the top (with pieces of tape). The split in the middle of the top turned out to be pretty serious. This was clear once the neck was removed:

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This split runs all the way to the neck block. It's movable with a little bit of force. Not good.

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A closer look at that F-hole. You can see the cloth backing that is holding the pieces together. I got some wood glue into the cracks and a little superglue underneath to hold the backing.

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A little clamping and wiping off of excess glue and it's done (hopefully).

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The split behind the bridge I filled with thin and medium cyanoacrylate. I had to switch to medium because it kept wicking away. This will hopefully keep the split from ever growing. I'll use a similar approach on the major top split, but use wood glue where the split is wide enough to get it in there. Ideally I should put a cleat on the back of these splits but that would involve removing the back of the guitar or doing some acrobatic clamping.

With all the cracks stable I don't have to worry about pressing too hard on the top and shattering it. So now I can get to cleaning this thing. A wet sock and some polishing compound turn this:

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to this:

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The difference is subtle but it turned out a lot of the nastyness of the top was just dirt and grime caked onto it.

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A shot of the whole top. All the cracks are stabilized and the finish is as good as it's going to be. I've considered refinishing the top but haven't decided yet. Except for the places where there is no finish at all it's really not that bad.

There's some really odd curvature on the back of this guitar. It's a difficult thing to capture in a picture but there is a big scoop in the middle towards the neck.

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Actually, what really is going on is the back is bulging out from either side of the neck block. If you peer inside you can see the back is peeling away from the neck block a little on either side of the block. I'm not sure what caused this or what could be done about it, but I'm leaving it alone.

Gluing pieces of wood back together is one thing... stripping off a 50 year old finish and redoing it with a spray can of lacquer is another. I'm not so sure this is a good idea. But the wife says it's ugly.

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All taped up and ready to be destroyed.

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There it is after a couple hours with 60 grit sandpaper. Most of the stains in the treble have been sanded out and the only thing that really stands out is the long cracks I superglued in the middle. The lumpiness in the center prevents those cracks from getting sanded flat so the glue shows a bit. There's still a few darker patches here and there where the old finish isn't quite gone - again, due to the lumpiness. Another couple hours of grinding on it should smooth it out. Good thing spruce is a soft wood.

Once I got it sanded down to 220 grit it was still a little rough. So I wetted the wood to raise the grain, then made another pass at 220 grit. When I did this a bunch of little pieces of the grain ripped up. Here's an example.

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Spruce is really weak and wet, sticky sandpaper just destroys it.

There's a lot of small grooves (see above) and dents in the top and that one big crack. I got some "natural color" wood putty from Stew-Mac. It's great stuff and really easy to work with. There's just one problem:

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It's not natural color at all. It's just white. This didn't really occur to me while I was applying it. When the wood is wetted down (to emulate the final lacquered appearance) it's really obvious. This putty thing was a mistake.

Death to the old putty, long live the new putty. This stuff is an oil-based putty that comes in a bunch of wood colors. You can mix the colors together like pain to get the right color. It dries, but not really very hard.

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I mixed these three colors together, dug out the top of the white putty, and filled in with the mixture. Not bad:

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The big crack is still noticeable but the rest of the top looks great. Even wetted down the putty isn't noticeable unless you're looking very closely. I can't say how it will look with lacquer but it could be worse.

Cracks are filled and everything is sanded down with 220 grit. I put a screw into the neck block so that I can hang it in my high-tech finishing chamber.

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I'll have to put some newspaper down before I start spraying.

Here's my finishing plans, essentially taken from Stew-Mac's instructions:

1. Sanded to 220 grit.
2. No grain filler since spruce is a tight-grained wood.
3. 4 coats of sealer (ColorTone Aerosol). 45 minutes between 1st and 2nd coat, 2 hours between subsequent coats.
4. 8 coats of lacquer (ColorTone Aerosol). Again, 2 hours between subsequent coats.
5. Sand (800 grit, wet sanding) and buff final finish.

You'd think there would be sanding between coats. Fresh nitro reacts with the nitro layer below it to kind of melt together, I think.

Here it is after 4 coats of sealer and 5 coats of clear coat. I've been leaving 4 hours or so between coats since that is recommended on the can.

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While the finish ages a bit on the top I refretted the neck. Nothing special here, just the usual defret, plane, refret.

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Since this is a bound fretboard the fret tangs must be undercut at either end. Stew-Mac sells an expensive tool for this but I saw someone else online had modified a sheet metal nibbler to do the same thing. I think I got mine on ebay for $12 or so. The modification just removes a little material to give the fret a lip to push up against so that the tang is right under the blade. It works great on this normal sized fretwire but had a hard time with the jumbo wire I used on a previous project. A little cleanup with a file is necessary after nibbling but it goes quickly.

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All I had on hand was 600 and 1500 grit sandpaper. So that's what I used. I wetsanded with 600 grit until most of the "orange paper"texture was gone from the finish, sanded with 1500 grit, and finished up with some rubbing compound. In a few spots I rubbed thru part of the finish along the grain lines. I think this happened because it wasn't perfectly sanded in that spot to begin with or some water seeped thru and caused the grain to swell. Either way, it's not really too bad because it makes the finish look just a little worn.

One of the cracks in near the bass F-hole re-cracked itself when I put a bit of pressure on the top during the sanding. I put a little cleat under the crack to make it more solid. When I clamped the cleat it left a really deep indentation in the top. I used the old wet paper towel and soldering iron trick to swell it back up. It worked really well. The top is a little wavy over that little spot, but it's not noticeable.

I didn't actually do a neck reset on this guitar. When I looked at the neck angle it seemed ok. So what I did was shim it so the neck joint would be tighter and glued it back on. The neck angle looks fine and the action can be adjusted lower than you'd want.

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The apparent high action on the higher frets is due to the fingerboard extension sloping down towards the body beginning around the 16th fret. It might have been better to plane that dip out, but not a huge deal as the higher frets rarely get played on non-cutaways.

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A brief youtube demo of this guitar.