Build Thread: Todd Rose Allegheny with adjustable neck

[Solariego]

Todd, would mind sharing your technique for getting the threaded inserts in straight (and securely)?

I'm still using Cumpiano's "bolt on" neck mod using furniture bolts and barrel nuts, mainly because it keeps me from having to deal with those threaded inserts.....

Thanks.

[Todd Rose]

For some reason, the third photo I tried to post in my last post above didn't show up, so here's trying again:

[Todd Rose]

Originally Posted by Rex Tremende

I'm really enjoying this fine thread. Thank you, Todd. Really beautiful work.

Thank you!

[Todd Rose]

Originally Posted by Solariego

Todd, would mind sharing your technique for getting the threaded inserts in straight (and securely)?

I'm still using Cumpiano's "bolt on" neck mod using furniture bolts and barrel nuts, mainly because it keeps me from having to deal with those threaded inserts.....

Thanks.

It's a challenge. The inserts not only don't want to go in straight, they want to tear out wood around the hole as they're first going in, pulling grain out rather than pulling the insert in. I wrestled with this some until I figured out a solution. The first thing is to drill the hole big enough, so it's not a tremendous fight to get the insert threaded into the wood. The threads don't have to bite in very deeply to be secure, especially after I drip a little CA glue in around the threads after installing the insert. The other thing I do - and this is the real key - is to use a guide I made. It's just a piece of 3/4 plywood (though I might make one out of aluminum or something) with a hole drilled through that matches the OD (outside diameter) of the threads on the threaded insert. I carefully line this up with the hole I've drilled in the workpiece and clamp it on. Then I put the insert through the guide and screw it into the workpiece (using an Allen wrench). The guide does two things. First, it keeps the insert going in straight and, second, it keeps the insert from tearing out the wood as it's threading in, because the guide hole ID is just a little bigger than the workpiece hole ID (plus I've chamfered the edge of the hole in the workpiece, so the two holes actually match just about exactly on the surface), and it's clamped on there good and tight. I hope that explanation is clear, as I don't have any photos of this in action.

[D.Kwasnycia]

This will shed some light on how I drill out the holes and put in the inserts. As Todd has stated, the hole drilled for the insert, must be larger than the minor diameter of the insert. For example, the inserts that I use have a minor diameter of .360 the hole size must be .390= 25/64.
I typically put a little bees wax on the threads to help when inserting the inserts and I turn the chuck by hand with the chuck key in place to add some leverage. As you can see, I have a fixture, that I use to use drill guides and to the left of the picture you can see that I have a number of different one's to step the drill size up. You can't just use a drill press unless, it is machine shop quality. I have found that the average drill press has a little movement in the chuck, so with the length of a drill bit, the play is multiplied. I also use drill stops, to help with the drill not going too far, if in the event it wants to grab and drill further than needed.
With my necks, the center being Rosewood and Maple, I don't have to be at all concerned about the inserts pulling out. If it were just Mahogany, I would have to do things differently.
Also, it does help to have a drill press that has a telescoping head and that can be swiveled to drive in the inserts as well.
Hope this helps.

[KevinLPederson]

To add to what Dennis, and/or any others do - you can use epoxy (instead of wax) and put on the threaded insert. It will actually "lubricate" the insert and then in a couple hours it hardens and strengthens up the "grip" and the wood fibers.

Kevin.

[D.Kwasnycia]

Originally Posted by KevinLPederson

To add to what Dennis, and/or any others do - you can use epoxy (instead of wax) and put on the threaded insert. It will actually "lubricate" the insert and then in a couple hours it hardens and strengthens up the "grip" and the wood fibers.

Kevin.

Good point!

[Todd Rose]

Thanks, Dennis. I think using a drill press to drive in threaded inserts is a very good idea. I've thought about doing it that way and may switch to that method at some point, but so far, my method using my little guide made from a scrap piece of plywood has been working well for me.

One thing to note that's different about the way I'm doing this: due to the unusual neck construction, one aspect of which is that the grain of my heel block runs perpendicular to the neck shaft rather than parallel to it, I'm putting the threaded insert into side grain, not end grain. Apparently, Dennis has found that putting the inserts into the end grain of hard maple and rosewood works well, but, as he suggests, I would be wary of doing that with softer woods. One solution to that is to drill down through the heel and glue a dowel (of bigger diameter than the OD of the threaded inserts) in there, giving you side grain to drive the threaded inserts into. In any case, I would use some glue to help secure the inserts in place. Putting epoxy on the threads is a good idea. Carefully wicking in some thin CA around the threads after the inserts are installed is the method I've used. The CA not only bonds the inserts to the wood, it penetrates the wood and toughens it up a lot. (Depending on the epoxy you use, that may penetrate the wood somewhat as well).

[Solariego]

Originally Posted by Todd Rose

One solution to that is to drill down through the heel and glue a dowel (of bigger diameter than the OD of the threaded inserts) in there, giving you side grain to drive the threaded inserts into.

Ha, was thinking about suggesting the same thing to you. I've even considered it for the cumpiano design since those barrel nuts are still pulling against only about 1/2" of short grain....

anyway, looking forward to seeing how you attach that heel block to the neck....

[Todd Rose]

It took more problem solving to get to this point, but I'm finally almost ready to glue the heel to the neck shaft.





(The wood-cored carbon fiber rod isn't glued in yet.)

[Todd Rose]

By the way, I wanted to mention that I experimented with the drill press method of installing threaded inserts, and I will be switching to that method. Though my guide method was getting the inserts in adequately straight, the drill press method gets them in even straighter.

[Todd Rose]

The truss rod access channel is routed. The truss rod adjustment will be accessible under the fretboard extension, *above* the soundboard.




And finally, the heel is glued onto the neck shaft.




Starting to look like a guitar neck...

[Todd Rose]

The hole for the CF rod is extended through the neck shaft.




Testing the fit. The fretboard extension doesn't really curve downward, that's just a distortion from the camera. Anyway, this shot gives you a good picture of how the rod goes through the neck and heel, and how it will provide the necessary strength and rigidity to this critical area, which will handle a lot of load from string tension.

[Todd Rose]

Cutting the rod...



... and then sanding the ends to precise fit.

[Todd Rose]

And voila -



Next step is routing for the truss rod and two CF neck reinforcements. Maybe Monday...