Progress update for you, Bob.
First, after I got the rod out, I inadvertently re-invented a heat treatment device using a full-size steel garage cabinet. I noticed that the front face of one of the shelves was the same width as a bass neck, and the cabinet is 36" wide. So I clamped the neck completely flat to the front of the shelf, and plunked a cheap clothes iron down next to the twisted section. The heat from the iron warmed the steel shelf to about 150 degrees F, and I left it there for a few hours under heat. Unplugged the iron, left it to cool overnight, and in the morning the neck was almost straight--still had a bit of a deviation on the high side, up by the headstock, but vastly improved. Tried to get it totally flat, but further heat treating didn't accomplish anything much, and the glue line in the back of the neck started to worry me, so I just went on from there.
Got the rod down into the channel, it needed to be deepened about 1/16" to take the rod anchors. I did it with a jerry-rigged Dremel "router"--a piece of pipe nipple cut to the correct depth to hold the tool, and a tile cutter bit. Ugly but it worked pretty well, once I got the hang of it. Kept the tool speed way, way down and slowly cut the anchor points down to the correct depth. Then I sanded off the residual glue on the neck and the board, installed the rod (I left the lower original anchor in place and butted the lower rod anchor against it) and reset the fretboard pins. Glued up, got it into clamps against the same shelf again, left it for about fifteen hours. When it came out it was almost perfect. Still a bit of a dip on the high side, but close enough that I thought it might work.
Swapped necks on the bass, strung up without adjusting the truss rod--the strings pulled the neck fairly close to straight but the heel angle is way off (too high, strings are fretting themselves on the 24th fret). Raised the bridge all the way up and left the strings on overnight to make sure the neck would hold its position, but I want to give it a day or so just to be sure. Next step is to pull the neck off again to shim and shave the heel, and I might need to play with the first five frets a bit to get the action right, but otherwise this is coming along!
First, after I got the rod out, I inadvertently re-invented a heat treatment device using a full-size steel garage cabinet. I noticed that the front face of one of the shelves was the same width as a bass neck, and the cabinet is 36" wide. So I clamped the neck completely flat to the front of the shelf, and plunked a cheap clothes iron down next to the twisted section. The heat from the iron warmed the steel shelf to about 150 degrees F, and I left it there for a few hours under heat. Unplugged the iron, left it to cool overnight, and in the morning the neck was almost straight--still had a bit of a deviation on the high side, up by the headstock, but vastly improved. Tried to get it totally flat, but further heat treating didn't accomplish anything much, and the glue line in the back of the neck started to worry me, so I just went on from there.
Got the rod down into the channel, it needed to be deepened about 1/16" to take the rod anchors. I did it with a jerry-rigged Dremel "router"--a piece of pipe nipple cut to the correct depth to hold the tool, and a tile cutter bit. Ugly but it worked pretty well, once I got the hang of it. Kept the tool speed way, way down and slowly cut the anchor points down to the correct depth. Then I sanded off the residual glue on the neck and the board, installed the rod (I left the lower original anchor in place and butted the lower rod anchor against it) and reset the fretboard pins. Glued up, got it into clamps against the same shelf again, left it for about fifteen hours. When it came out it was almost perfect. Still a bit of a dip on the high side, but close enough that I thought it might work.
Swapped necks on the bass, strung up without adjusting the truss rod--the strings pulled the neck fairly close to straight but the heel angle is way off (too high, strings are fretting themselves on the 24th fret). Raised the bridge all the way up and left the strings on overnight to make sure the neck would hold its position, but I want to give it a day or so just to be sure. Next step is to pull the neck off again to shim and shave the heel, and I might need to play with the first five frets a bit to get the action right, but otherwise this is coming along!
