Crawls Backward (When Alarmed): Compression Fretting to Correct Backbow: 1931 Martin 0-18T Restoration and Repair, Pt. 10

Finally we're ready to refret the 0-18T!

I took some measurements of the old frets compared to the new ones and found that the tang was about .029 in. compared to the new ones, which are .023.

I'm doing a compression fret job to correct the backbow of the neck from the first to about the fifth frets. What this means in a nutshell is that we'll put frets that have a slightly wider tang than the fret slots, so they will 'compress,' or force the neck into a upbow. Then under string tension, the neck will be pulled straight.

And by slightly wider, we're talking a thousandth of an inch or so.

The new frets' tang measures .023 inch. So ideally we want to have a tang width of .024 of an inch or thereabouts for the compression. But since the old slots are about 5 thousandths (.005) too wide, I'm going to fill the slots with ebony sawdust and then make newish slots.

I just filled the slots and used super glue to hold the sawdust in place, as I would on a hole or chip fill. That's the easy part.

Rather than use my big fret slotting saw, I used a fret slot cleaning tool - which is .020 inches wide.

The saw has two blades - one for the push cut and one for the pull cut. Very handy, and a lot easier to control than the slotting saw.

Along with cutting the "new" slots, I'm checking the depth of the slots with a depth gauge to make sure the new frets will seat properly.

This job is looking like a Stew-Mac ad. I really, really would like an endorsement deal.

Although the slot cleaning tool is .020 wide, I'm not surprised to find that the slots wind up a bit wider than that - about .024. I say I'm not surprised, because the dust/glue mixture is softer than the ebony on its own would be, so the slots are just that smaller amount wider than the kerf of the tool is.

This is ok, not a problem at all.

The main thing is that they are no longer .029 wide, which is where they were originally.

Now we take a length of fretwire and run it through the fret bender.

Although the fretboard is flat, I want just a small radius on the wire so the ends will sit into place before the frets are pressed in.

Those people in Ohio have everything for every repair situation.

A gentle squeeze with this fret tang tool will make the tang compress and get a tiny bit wider.

I found the tool does leave small tooth marks on the crown of the fret, but they disappear when the fret gets dressed.

Well, gol-lee.

After a bit of squeezing, our .023-wide tang has become .025!

Exactly what the doctor ordered for our .024-wide slots.

I think this might work!

Now we press our new frets in with the Jaws (actually a modified Facom press) fret press.

This tool is great, but I have to relearn how to use it each time I do a fret job, since I don't do a lot of them.

Note that I have strings on the guitar - I installed a few frets and then tuned it to tension to get an idea of how the neck would look under tension before I put all of the frets on. It looked good with just a few frets installed.

The Jaws press doesn't work on the frets over the body, so there I have to hammer them in the traditional way.

Note that I have a brace jack inside the body to support it. I did see plans for an elegant fingerboard support online and I want to make one. But for now, the jack works perfectly well.

Frets are all installed. They need to be levelled, trimmed and crowned.

The neck looks good and straight at this point.

We use our trusty Corian fret leveller and 320 grit paper to level the frets.

Then clip the overhanging ends.

And next, file the fret ends to a 30 degree bevel.

And finally crown and polish them.

I'm leaving some details out - some of my older posts have more detail on this process.

After the frets were dressed, I put some fretboard oil on the board. It took 2 passes - the old, dry board just soaked the stuff up.

I also used it on the bridge, which is also ebony.

Made a nice new saddle out of unbleached bone, and set the action.

The neck now has a perfect angle, and there is just a bit of relief - maybe .015 inch. A tad more than I'd like, but considering we started with about a 1/4 inch backbow (!) I think we're in good shape.

It plays really well now - and sounds great. The neck is a bit chunkier than my other 0-18T.

In the next post I'll have some pictures of the completed guitar.

All posts in the 1931 Martin 0-18T Restoration Project:

Crawls Backward (When Alarmed)

1/4/17

Compression Fretting to Correct Backbow: 1931 Martin 0-18T Restoration and Repair, Pt. 10

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