Bolt on neck - laminate the tenon?

[NeilG495]

Looking to try my first barrel bolt on neck and wondered if there are any obvious pitfalls to watch out for when installing them. For my last 4 builds I used Cumpiano’s hard wood taper pins, which have worked well but they are very fiddly. I notice Cumpiano has now moved to barrel bolts but he cuts his tenon thinner then laminates either side of the tenon cheeks for added strength - is this absolutely nessessary? Anyone experienced the barrel bolts cracking the tenon?

[John Parchem]

I put them in without laminating for strength. I would suggest either installing them before cutting the tenon, or to clamp the cutoff on both side of the tenon when installing them otherwise it is possible to crack the tenon while installing them. There are multiple brass inserts that look the same but not all of them are good for end grain. Here is a url for good ones http://www.essentracomponents.com/shop/ ... reId=10152. This is the kind that Martin uses.

Oh and the slot is not for screwdrivers rather it is a thread cutter and goes down while installing.

[NeilG495]

That’s interesting, I had no idea Martin used this design. How do you install them? Is it just a case of drilling the right size hole and then screwing them in with a screwdriver? I’ve already cut the tenon, as I was going to use the wooden pins. I don’t know how much effort is needed to screw these brass inserts in but I wouldn’t want to risk cracking the tenon.

The bolts I was thinking of is the barrel bolt that Cumpiano and others use. These are a simple horizontal barrel, pushed in the side of the tenon, that takes the bolt 90 deg to it. Do you think the Martin insert is a better option?

https://www.cumpiano.com/an-improved-neck-body-joint

[John Parchem]

Martin does both bolt on and dovetail depending on the model.

You drill the right size hole, the straighter the better and then you screw them in. Not with a screwdriver, the slot is for cutting, I get a relatively long bolt with two nuts. The nuts go on first then thread the insert on use the two nuts to lock the insert in place then screw the insert into the wood just like you tap a screw hole.

With the tenon cut, i clamp wood on both sides of the tenon and the back of the tenon to prevent the tenon from cracking. These inserts are cutting wood so they are not likely to split the tenon. I just like to be safe.

[John Link]

David Russell Young proposed that if you make a neck that can be reset, it WILL need resetting in its future. Somogyi does a M&T neck joint, but then sinks dowels bridging the joint on both sides, and finally adds CF reinforcement at the top of the joint that spans the fingerboard and heel block. It is still possible to reset the angle by slipping the block, that is by loosening the back part way towards the end block, then pushing the neck down to restore the angle and re-gluing the back. I am using this technique on a 100 year old Oscar Schmidt "Hawaiian" guitar and so far, using just clamps to test the idea, it looks like it will work. (The "Hawaiian" was designed with a high action for a slide that used the frets only as a guide for delineating the various notes. They make great blues guitars, however, with a nice growling bass and bright treble. But they need to be adjusted to play normally.)

For what it is worth, I built a DRY type non-adjustable butt joint (with some modification) 12 string, 14 fret neck, that has been strung full tension for 40 years and the angle has not changed. As DRY said, make the joint so it can be changed, and it will change, all on its own, from string tension.

All that said, I respect that making a Spanish style solid joint is not what you are after. It is offered only in the case that you get tired with fooling around with the proper bolts and inserts, in which case you can insert the dowels and be done with it.