Official Luthiers Forum!

As I work on getting closer to the fit and finish that I'm looking for there are a couple of challenges that I don't seem to be able to figure out. One is achieving a very close fit between neck and body. I'm using a bolt on M&T neck, and and familiar with the techniques of using a chisel to pare away from neck on the endgrain, then using sandpaper to floss away the high spots on the neck as it joins the body.

Where I'm struggling is that the joint doesn't seem to be responding in a predictable way to removing material on the side of the neck which is snug (so as to allow the neck on the other side of the tenon to get closer to the body).

What am I missing? Is there something to the geometry of this that tricky? Thanks.

Corky-
A couple of possibilities spring to mind:
-'Rocking' on the wood closer to the tenon-have you 'undercut' the wood closer to the tenon, so that the heel is only touching the body at the edges?
-Tenon bottoming in the mortise, or tenon fitting tightly enough so that the neck cannot 'pivot' side-to-side.

I keep some (kid's) colored chalk in the shop- sometimes coating one surface with chalk and fitting the joint will reveal the interference point more clearly.

Cheers
John

Corky: When fitting neck to body I find it imparitive to make sure the end of the body where the neck fits is dead flat. I use a flat block so I check two ways 90 degrees apart. If the top of your body is radiused then you must check to see it is flat top to bottom. If you use a tight fit on the tenon and are trying to get the neck aligned with the centre line you may have a bit of trouble and will have to loosen the fit a tad. Not much more I can add,hope you can follow what I'm trying to get across. Good luck.
Tom

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A person who has never made a mistake has never made anything!!!

John's a much faster typer and adds some good points.
Tom

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A person who has never made a mistake has never made anything!!!

I think I should get myself down to the shop instead of daydreaming at the computer!!

John

Instead of "flossing" (strange vernacular…) try PSA sandpaper and move the neck back and forth. It really helps also to undercut the neck cheeks and leave only about 1/16" edge. Apply more pressure where needed and try to get as close as possible with a sharp chisel. Chalk on the neck heel helps to see where you're at.

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Laurent Brondel
West Paris, Maine - USA
http://www.laurentbrondel.com/

There are a lot of little things that you might not think of as well. A tiny bead of glue you missed when you glued the fret board on, the end of the tenon touching the bottom of the mortise, the truss rod nut not clearing it's slot, etc.

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It's not what you don't know that hurts you, it's what you do know that's wrong.

Corky,check out Hesh`s tutorial.I use the same joint as you,and get a nice tight fit.Do as Laurent said and use more force where needed.I use a huge amount of force when doing this,without any problems.
James

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James W Bolan
Nashville Tennessee

I've had best luck rubbing the neck against the body when that part of the body is really flat. Also rubbing in only one direction.

Thanks, all.

I'll try these suggestions. The "dead flat" objective on the body is probably one issue. It's probably not quite flat, making the matching of two slight curves a very challenging process. Thanks!

I had the same problem recently fitting to a (quite curvy) guitar body. Make sure you undercut the cheeks enough.

It looks better than a 'square guitar' when it's done, though!

If the curve is 'across' the side (e.g. the bindings were scraped down a bit extra), try your best to get it 'flat' in that direction.

John

All the suggestions here are good ones. The most frustrating time I had was when the sides weren't flat. I kept sanding away until the twelfth fret was well over the body, instead of being right at the body joint & still couldn't get a gap free fit.
I ended up gluing an ebony shim to the shoulder (to get the scale length correct & the 12th fret back where it belonged), block sanding the upper section of the body & starting again. Everything worked out fine, once I did this. (And the ebony shim looks very cool!)
If the body is fairly "curvy" at the heel joint, Draw a pencil line on the sides, along the edges of the heel. Lay a good straight edge along the line. Any dips or humps will make getting a good fit nearly impossible.