BOLTED NECK JOINT - THREADED BRASS INSERTS

[H165]

I'm building another resophonic. Here's some bolted neck joint detail - threaded brass inserts.

My local builders club got to tour Kevin Ryan's shop. I HIGHLY recommend this if you get the opportunity. On my reso build, I decided to use the the 1/4"-20 brass inserts Kevin showed us. I drilled .312" and tapped, rather than drilling the manufacturer-recommended .375 hole. I think the slotted brass thread cutters are a bit soft on the inserts, so, as recommended in a previous internet post, I made a tap from a galvanized 3/8" lag bolt (it's a very close thread match). I slotted the lag bolt threads on a slight undercut angle, which made cutting edges on the threads. I used JB Weld for a bit of insurance.

[fazool]

Great approach and well engineered tooling improvisation.

[HarryQ]

Thanks for the useful information! Did you use any aids to make sure the holes were squared up to the tenon when you drilled them? I'll be doing a butt joint neck soon, and would appreciate any tips. Great work!

[Big Band Guitar]

You can get those in stainless and eliminate the tapping step.

[phavriluk]

For those who don't want to improvise a tool to drive in threaded inserts, I've found them at Woodworker's Warehouse, in many thread sizes. Nice part about them is they are t-handled (look like hex keys) and being so, are easy to use to center the threaded insert in the hole.

As for the threaded insert tap, that's by my lights a real stroke of inspired innovation. Never would have thought of it by myself. And it's so nice to have a tool that helps remove some of the worry about splitting the heel.

Thanks very much!

[murrmac123]

Forgive me for being dim, but you have a maple neck, and you have installed a tenon of a different wood, am I right ?

Also, I may be mistaken here, but from the pictures, the tenon seems to have the same grain orientation as the neck ?

[LouieAtienza]

Originally Posted by murrmac123

Forgive me for being dim, but you have a maple neck, and you have installed a tenon of a different wood, am I right ?

Also, I may be mistaken here, but from the pictures, the tenon seems to have the same grain orientation as the neck ?

Looks like a 3 piece neck Murr.....

[H165]

Did you use any aids to make sure the holes were squared up to the tenon when you drilled them?

Yes; I put the drill press table at 90 degrees (parallel with the drill bit) and then put a plumb line on the table. I did a few other things to ensure the inserts went in square. There are a few YouTube tutorials out there like this one:

https://www.youtube.com/watch?v=tIhEqoKE8Dc

....you have a maple neck, and you have installed a tenon of a different wood, am I right ?

....from the pictures, the tenon seems to have the same grain orientation as the neck ?

You are correct, however the tenon is actually integral to the neck. The neck is made of three pieces of wood. The tenon is part of the center piece. The tenon appears darker than the rest of the center piece, because Kevin Ryan also showed us the technique of saturating the end-grain tenon area with super-glue to harden the tenon.

You are correct, all three pieces are end-grain in the pictures. I assume you are alluding to the fact that the end-grain has less holding power than cross-grain. This is why Ryan (and now I) apply super-glue. You'd be surprised how far that stuff penetrates. Here's a better picture:

[LouieAtienza]

Originally Posted by H165

Yes; I put the drill press table at 90 degrees (parallel with the drill bit) and then put a plumb line on the table. I did a few other things to ensure the inserts went in square.

Great idea with the drill press... I no longer own a free-standing drill press so that's difficult for me. I made a jig where I did drill a guide block on a rather thick piece of wood, and a long board which this block is glued onto with guides to hold the blank square, and drill with an aircraft bit.

Great idea on the CA glue. I met Kevin Ryan in 2016 at Woodstock, and one could not meet a nicer guy who was ready and willing to talk shop!

[H165]

You can get those in stainless and eliminate the tapping step.

Excellent. Where can I get these?

[Big Band Guitar]

Originally Posted by H165

Excellent. Where can I get these?

https://www.boltdepot.com/Threaded_i...teel_18-8.aspx

[H165]

OK - I see them - Thank you!

[LouieAtienza]

I personally would still tap the holes. This way, you're cutting the threads not displacing wood- and that could have disastrous results depending on what wood you use.

Or better yet, use threaded studs on the neck heel, and use cap bolts (internally threaded) inside the guitar. Since yo only have to put the threaded studs in once, you have no need for grommets and the threaded studs have a coarse thread, and smaller diameter than an insert.

[Quickstep192]

On the topic of stainless steel...

I love the idea of pre-tapping for the insert. It looks like it makes for a better purchase and makes it easier to drive. It occurs to me that Stainless Steel lag bolts have really sharp threads and may make for a better tap than a galvanized lag.

[redir]

I've done it that way on quite a few guitars though not a tenon but a butt joint. I do now use a dowel though. Having had one heal crack at the insert was enough for me to rethink it.

And I did used to, and still do, flood the face with thin CA. I also like to epoxy the inserts in for good measure.