Bolt-on neck threaded insert question

[Diane Kauffmds]

I helped someone who needed to modify the mortise and tenon, because the holes in the mortise didn't match up to the inserts in the tenon. It's a long story and I know it will sound a bit confusing, but what you need to know is how I fixed it.

I had to modify the mortise and tenon by drilling a new hole in the neck block to match one insert in the tenon; then I had to install a new insert in the tenon to match the one of the existing holes in the neck block.

I made a wooden caul that fit tightly around the tenon, to prevent it from cracking while I predrilled the hole and screwed in the new insert. The neck was clamped into the worktable. I drilled the hole with my hand drill. (I have a square that I made out of 2 pieces of 1 1/2" x 4" wood, which are joined at a right angle. I put the bit into the corner of the angle, so that I know that I'm drilling straight.) I made the hole just a smidgen smaller than the hardware. I put some thin ca glue into the hole that I drilled, then screwed in the hardware. The glue lubricated the brass just fine and it went in easily. It's well secured and won't come out.

Then, the guitar box was clamped into a worktable, and I drilled the new hole in the neck block. The position of the new brass insert for the tenon was easy. I put the neck into the block and marked through the existing hole in the mortise. For the position of the new hole in the tenon, I measured it's new position with a caliper.

As you can see, they matched perfectly.

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