Dove tail neck angle - first time builder - help wanted

[dodt14]

Hey Folks,
I'm having a bit of trouble getting the correct neck angle on my first build. I'm using the pre-fab stew-mac dovetail neck and neck block.

Here's my problem. I must have installed the neck block a little less than perfect because when I started to try and get my neck angle right it started off with the the headstock angled upwards when the guitar is laid on its back and I believe it should be angled slightly downward in order to create the opposite angle. For example, when I initially put a straight edge on my neck and across the body there was no gap near the bridge. In fact, initially the straightedge was flush with the neck, then there was a gap where the body started and then it was flush after the sound hole, which told me that the angle was going in the wrong direction. I could see it without the straight edge as well.

So, I've taken the neck angle back as far as I can and I need to go a little further to get it right... but the tenon won't let me because it's tilted so far back that it's hitting the neck block. There's no more room to move.

The only thing I can think to do is sand the bottom of the tenon so it's not as deep and so it will allow me to get a little more angle. And I'm guessing I'd then need to make a shim on the sides of the tenon to ensure the joint is wide enough to create some grip on the dovetail.

Does that sound right or should I not touch it and just take it as it is...or should I give up and buy a motorcycle instead?

Thanks,
John

[Bruce Sexauer]

With a dove tail connection the geometry is controlled by the cheeks of the heel, and the dovetail itself is adjusted to make everything come together solidly. This latter can be done with shims to no ill effect, though pros will politely look away and try not to catch each other's eyes. The goal is for the fret's final surface to line up close to exactly with the top of the finished bridge surface, for most of us. So, if your description of the neck lining up with the top at the bridge is w/o the fingerbpoqrd, you are right about where you'd want to be. but is it is the fingerboard surface projecting to the top at the bridge footprint area, you have some work to do.

Buy a motorcycle anyway, I have a couple for sale.

[tahoeguitar]

Your neck angle is about right when a straight edge laid on the FB with no frets is right at the top of the bridge. In other words the Fretboard plane should align with the top of the bridge. The rule of thumb for a guitar that is already done and strung up for awhile is that the "top of the frets" plane should align with the top of the bridge. If it's below the bridge you'll have a low saddle and if it's above the bridge a tall saddle. Aligning the bare fretboard with the top of the bridge allows 40-50 thousandths of an inch for your top to belly up. Your saddle will be tall at first but most guitars will belly enough unless they're overbuilt. IMO YMMV etc...

Grinding off the back of the tenon and installing side shims is no big deal and I've seen it a few times even on new factory guitars. One of the dirty tricks I use is to glue a 1/4" square "dot" of shim material that is a little thicker than what I think I'll need to either side of the tenon. Then fit and file. When it fits that tells you how thick to make your side shims. The dot is much quicker to file and fit than a whole shim.



Get a dirt bike. Way more fun than a street bike IMO... Riding on the street with all these tons of metal behemoths darting around me scares the crap out of me. You have to be so focused just to keep from getting run over that it takes most of the fun out of it for me.

[John Arnold]

You have it right. Trim the end of the tenon (I use a chisel, mostly), trim the heel to the proper angle and fit to the sides, then shim the joint so that the neck surface is flush with the top with some clamping pressure.
For ease of removal later, you need at least some space between the end of the tenon and the neck block. That allows steam to enter the joint. Do not put glue on the end of the tenon. The angled cheeks of the dovetail are what hold the neck in place.

Ideally, the neck will start out above the top. That way, you can trim the heel to the proper angle first, then trim the dovetail to fit. When the neck is above the top, you can check the angle with a straightedge by subtracting the amount sticking up from the measurement at the bridge. If everything goes well, the result is the right angle and dovetail fit using no shims. But, IMHO, there is no shame in using shims. Some of the best 1930's Martins I have ever played had shims from the factory.....usually made of holly veneer. In addition, virtually all dovetail resets involve using shims.

With no fingerboard, I like for the straightedge on the neck surface to be about 0.110" above the top at the bridge.
With the straightedge on top of the frets, I want it to be 0.390" above the top at the bridge, or 0.045" above the bridge.

My numbers:
Fingerboard + fret thickness = 0.280" (0.235" fingerboard, 0.045" frets)
Bridge thickness = 0.345"