What is the best method...

[Ben-Had]

for lining up and drilling the hole in the neck block to match the threaded insert in the neck tenon on an M&T bolt on? This will be my first M&T and the neck block came un-drilled.

[RnB]

I'd like to know this also, since I keep pulling the brass threaded nut out of the tenon on the one I'm working on. It came out once & I super-glued back in place. Then, when mounting the neck again, the wood cracked on the tenon around the nut in two places. I back-filled the cracks w/ medium viscosity super-glue & it seems to be OK, but I was thinking of adding another bolt for added strength. Not sure if it's a necessity though, since the neck will be glued-up in the end...?

[tippie53]

There are a number of ways to do this. If you are doing prior to gluing on the block , you need to allow a little fudge room. My best advice is to make a simple jig if you make it L shaped so the bottom let of the L catches the top of the block . Mark a center line to this. For the neck block use a shim to off set the thickness of the top. Remove the shim for the neck so the holes offset that thickness.
Use a small diameter hole say 1/16 as the mark hole then you can use that as the center hole for the bolt and the threaded insert If you let the neck go until the body is done you can plot the hole location using the neck block holes themselves for the points on the neck.

[Ben-Had]

Thanks John, that makes good sense. Do you suggest 1 or 2 bolts?

[Kevin Sjostrand]

Rick, that's what I was going to say! Pretty easy.

Kevin

[Ben-Had]

Sounds like a good process as well. A little more expensive having to get those pieces ($40-50).

I have a follow up question. The hole for a 1/4-20 threaded insert is about 15/32", slightly less than a 1/2". Would you use a 1/2" dowel center point or would that widen the insert hole? Wouldn't want to screw up the holes.

[Kevin Sjostrand]

You don't need super precision here and actually it is good to have the holes a little bit oversize, so if you are not exactly on center, it is not a problem. Over size them to at least 5/16.

Kevin

[Kevin Sjostrand]

I suppose it depends on how good a fit you have with your mortise and tenon, and center alignment, to begin with. I have found that giving the bolts a little room helps allow the neck to body fit to adjust if you need to bring the neck on center....but then, as you said, that is an engineering thing, if it is right to begin with then there would be no need for oversized holes....
I am no expert here, that is for sure. I'm still a young'in builder! :>)

Kevin

[RnB]

Frets.com has a page on neck re-do on a Spanish Heel. Some of Frank Ford's inventiveness s comes through as he makes a tool for a counter-bore....
http://frets.com/FretsPages/Luthier/Tec ... eset4.html

I once did a conversion on a Spanish Heel on a beater guitar my wife brought home. It came out OK, but I though it lost some of it's bass response in the process. I ended up giving it to a young kid who was just beginning to play.

I thought I read somewhere that you could do a counter-bore using a Spade Bit, but running it in reverse. Out of curiosity, I gave it a try today w/ an old 11/16" spade bit I had. The 1st try: while it did a bore, it was more conically shaped than a Forstner shaped bore due to the shoulders at the bottom of the bit. From there, I took a hack saw & cut the shoulders off (admittedly,very crudely), then ground off the rough edges w/ a bench sander. I tried putting a sharper edge on the new bottom, but I was running out of time & abandoned that.

2nd try: After drilling a hole the size of the shank in a piece of scrap I chucked the spade bit in a cordless drill, after putting it throught the hole first. I then ran the drill, but not in reverse, pulling it backwards. Without too much effort, the result was a decent counter-bore. I think if I'd been a little more careful shaping the bit from the start, there would hardly any detection of how the bore was done. It only took about 15 mins time to cut the bit. Since I usually put covers over the holes...not too much would be obvious.

[Ben-Had]

That's a great idea. Cheap too. Thanks.