This particular classical guitar came into the shop with a swollen belly and dipping chest. The action was so high you could put your entire hand under the strings at the 14th fret. After tightening up the bracing and flattening the belly, I was still stuck with an action to uncomfortable to play. Just under 1/4"... The Owner loved the sound but was prepared to toss this guitar in the trash and buy a new one. I had to say NOOOOO!... Give me a shot at her, and he agreed. He doesn't care what she looks like as long as she plays and sounds great.
This guitar was built in Mexico sometime in the 1960's, and surprisingly was built in the style of the masters like Torres and Houser in the 1800's. Not Well Built, but Built using their techniques. Specifically the neck attachment. No Bolts or Dovetails here. Only the slots in the side of the heal of the neck where the body sides integrated into the neck. This makes a neck adjustment next to impossible. Especially an adjustment the size of what I needed here.
What's the answer here... a Shim. I'm going to shim the Fretboard.
First step here is to remove the fretboard. In the pics above you can see I used a silicone heating blanket with a steel weight to hold it down. As the glue loosened I gently slid a palette knife between the neck and fretboard followed by a sheet of wax paper. Little by little I worked the heating blanket from the sound hole to the nut, eventually removing the fret board completely.Next I glued an 1/8" sheet of Cherry to the fretboard. Why Cherry... for some reason I have a lot of Cherry around... and No Rosewood. After a couple of days for the glue to dry I began working on the shim. Using hand planes and eventually a flat sander. From the above pics you can see the final shim. After a succession of test fits I ended up with the Shim at 3/16" at the sound hole end and it tapers to the first fret. This should give me the lift to solve the action problem.Gluing the Fretboard back on to the neck is clamps galore and a couple of days dry time. Once dry I used a scraper to remove any overflow. Here you can see the shim at the 12 fret.
A little bit of stain and finish and she's strung up and playable again. Action at the 12th fret is around 3/32", perfect for a light touch. The Customer Flipped out. He'll be using this in the recording studio soon.
I'm happy I was able to save another one from the scrap heap.