Scarf joint versus one-piece neck?
 

Can anyone please tell me about the relative merits (or otherwise) of a scarf joint compared to a one-piece mahogany neck?

Fliss

Necks cut from a single piece have "short grain" in the headstock. This weakens the neck substantially.

One of the ways around this problem (and it also has the benefit of using less neck stock) is to cut a scarf joint from the same board, reverse the piece, and glue it on at the headstock angle. This gives you "long grain" on both the neck and the head stock. Provided you have a good glue joint these are much stronger than normal 1 piece construction.

Another way to deal with the weaker neck due to short grain on single piece necks is to use a backstrap of veneer behind the headstock. This also reinforces the headstock area of the neck considerably on single piece necks. (This is how I do it).

Despite the fact that both the scarf joint and the back strap are much stronger than a 1 piece neck there are bazillions of 1 piece necks that never have any problems.

Wow, what a fast and informative response - many thanks, Brock :)

Fliss

I used to hang with a couple of repairmen who said that although breaks happened, the most consistently problematic were Gibson electrics due to the incredibly insane thinness at the truss rod bolt area, just at the place headstock joined. My old NY Epiphone certainly broke easily there, and it was realllllly thin.

Don't many luthiers who hand carve their necks use a volute due to the vulnerability of the area where the headstock meets the neck. Both of my House guitars had a rear headstock veneer and volutes.

I think it depends on the builder... A lot do, but I certainly would not say "most". Mine use both a smiley volute and a back strap veneer.

Isn't the neck surface of the scarf joint end grain? How do you make sure you get a good glue bond?

On most of my necks I use a diamond shaped volute. I do this for 2 reasons: First, I like the look of it and secodn is that I feel it gives some added "meat" to the neck area around the nut where it would be most likely to have problems. Keep in mind that I have had zero problems with a neck breaking, even ones without the volute.

Most of my guitars are one piece necks but recently I have been using necks laminated with a decorative stripe down the center. I have some necks that I carved but not installed yet that are scarfed joint, some single pieces of wood and some laminated. The scarf joint definitely uses less wood to produce, so this is sometimes appealing to people who are enviornmentalist minded. The laminated necks would be the second in terms of wood used while the one piece neck uses the most wood.

I think that any luthier/builder is going to make sure that you wont have problems with the instruments you buy from them, so they will make a neck they feel is strong and secure while also filling your needs for playability.

What about luthiers who use 3 and 5 piece necks with no scarf, backstrap, or volute? Are they strong?

I think practically speaking all of these will work fine. As I mentioned above, there are tons of 1 piece necks that are doing fine after decades of use.

But in the strict sense of the word, the short grain is weaker than the long grain.

Laminations can help, but there too you have short grain in the laminations. And the volutes and back straps help a lot too.

Again, practically speaking it would be a non issue if I liked a guitar.

The 15 deg tapered cut makes for a long gluing surface. No problem gluing.

Multi-lam necks are supposed to have less warpage however, that point can be argued plenty.but this important for Guitar Picks,suppose I've worked with a some single-piece quartersawn necks that are easily as strong and stable as some laminate necks, maybe a little more so. But a lot of manufacturers and builders make all of their necks from multiple pieces and they turn out to be quite exceptional. The strength and stability of a multi-lam neck will also depend on how the grain of each individual piece is oriented.

There is nothing wrong with using a scarf joint and as Brock points out it has some merit. Another merit is that you can use much less raw material, that is if you use some sort of "glue-up" when making the heel of the neck. I have done a stacked heel on a couple of early guitars (along with the scarf joint) and although this is fine, I was not crazy about the stacked heel. It was fine, I just didn't like the look. Also if you want laminates running the length of the neck, it could be challenging to get it to align properly when doing a scarf joint. I guess one could add the laminates after the scarf joint by slicing the glued up neck in half. It is a little more challenging than that as one should be concerned with making sure the grain is going the right way to.

My only reason to return to using a scarf joint would be to save material. As it is now, I am left with a fairly large piece of neck blank material, but I always seem to find a use for leftovers wether it is making some jig, or even business card holders.

can someone post some pictures of a "scarf" joint?

Some of my guitars have an area that looks like a big frown near the top of the neck. Others have a straight line across the headstock.

Many of the old Regal parlors I work with have a scarf joint at the headstock. Most of these are 60+ years old and I've yet to come across one that has failed.