Crawls Backward (When Alarmed)

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Neck Reset on 1927 Martin 5-17T Tenor Guitar

It's going to be a couple of weeks until I get back to the Martin O-18T.  I'll finish spraying it, and the lacquer needs to cure a bit before I can rub it out.

That doesn't mean there's any halt in projects in the Dungeon. 

Here we have yet another tenor guitar.  Crazy, huh?

This one is a 1927 Martin 5-17T.  All mahogany (aka 'hog'), and small Size 5 body.  It needs a neck reset.

The original bridge pins are long gone.  Someone made some to fit the guitar, but unfortunately there are only 3 left.  So I just strung it up with 3 strings so I could measure the neck set under tension.  I don't think one missing string will make much difference.

I've written about neck sets before - so this is a very quick overview of the process.  With a straightedge on the fretboard, we see where it falls when it hits the bridge.  It should be just at the top of the bridge.  Here, it's clearly not.  It's about 1/8 of an inch below.  Armed with that measurement, we can calculate the amount of material that needs to be removed from the base of the neck heel to correct the neck angle, and therefore the set of the neck.

The bridge pins were nicely done!  If I had all four, I'd reuse them.  They're hardwood, and were turned on a lathe.  Compare this work to the old bridge on my O-18T.  If only this craftsman had done that bridge.

To remove the neck, I'll use steam.  We drill a small hole in the fingerboard to get a steam needle into the dovetail joint that joins the neck to the body.  I'll drill that hole in the fret slot above the joint - in this case it's the 13th fret.

All Martins made before 1934 or so used bar frets.  Unlike modern "T" shaped frets, these were cut from rectangular bar stock.  Removing the fret is just like a modern fret - some heat with a soldering gun, and a gentle back-and-forth with nippers to lift the fret out.

It came out perfectly with no chips!  This is going too well.

You can see the hole (I think it was 7/64) in the board.  It goes right down into the dovetail.  Unfortunately, I got a chip that came out of the rosewood.  No big deal though - I'll just glue it back into place later.

I heated the fingerboard extension and used my trusty removal knife to loosen it.

These old Martins were made with hide glue - and this disassembles like a dream.  If only my Guild F-50 had been this easy.

Next, I'll put the guitar in my neck removal jig, run some steam down into joint and get it apart.

Talk about an easy job!

I put the guitar into the jig, and applied a little pressure on the heel.  Pop!  The neck came right out.

Turns out the craftsman used glue very sparingly on the guitar.  It's now brittle, so it came right apart without steaming!  The joint fits nice and tight.  Super workmanship.

I was so happy that I just dashed though the chisel-and-filing part of the work on the neck heel and didn't get any pictures.  The dovetail is like a smaller version of a standard Martin joint - but a bit more delicate and almost dainty.

When I went to heat up my hide glue, I figured I might see how accurate my old Pyrex instant read thermometer is.  I recently got a super accurate Thermapen for cooking.

You can see the results.  At 145 degrees F (where we want the glue to be), the Pyrex reads about 160!  So all of my past jobs have used glue at a lower temperature than it should be.  But now I have a reference on the Pyrex so I can just use 160 instead.

No wonder all the steaks I cooked using the Pyrex were more done than I wanted.  Hmmm.

With my glue at the correct temperature (ahem), I reglue the neck joint.  I'll let it dry overnight, then I can clean up the fingerboard, give it a level and crown, make a new saddle, and string it up.


Post a Comment 1 comments:

  • July 22, 2013 at 7:47 PM
    Hey, nice job and documentation. I need to go back and read more.
    Thanks for posting all this interesting info.

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