Neck Block Grain Direction- Steel String Guitar

[Charlie Dunford]

I am about to install the neck block on a new guitar build and have a question about which way to orient the end grain of the block.  Most luthiers recommend that the grain of the block should be parallel to the grain of the sides, but that is about as far as it goes.  If you do that and you have vertical grain neck block material you have a choice of orienting the block with the growth rings going up and down (parallel to the sides), or fwd and aft (parallel to the top/back of the guitar).

I am trying to decide which growth ring orientation is best for a Dovetail neck joint. My concerns is about differential shrinkage where the neck block, sides and neck combine to make the dovetail joint.  I hope there is someone out here who can answer this question.

Thanks in advance to anyone who takes the time to respond to this post.

Charlie Dunford

Hansville, Wa.

[William F.Eden]

 There will be pros and cons about both ways so you may as well do it what ever way you like.I like it to go up and down myself but that is just me. Bill................

[harrison phipps]

The orientation of the headblock grain parallel to the sides gives you a good gluing surface for the top & back avoiding the endgrain parts of the headblock which do not hold as well.  Although I prefer vertical grain for the plates of the guitar, I avoid vertical grain in the head and tail blocks.  Some woods will split easiest along the growth rings or at a 90 degree angle to the growth rings.  By choosing block material with the grain at close to a 45 degree angle, I feel I have maximized the distance a split must take and therefore have maximized the strength of the block in the instrument.  If you are concerned about differential shrinkage, chose block material that has been sitting around for a decade or so.

[Donald A. Fortune]

Hi Charlie- Ive always put the block with the grain direction going with the sides- never failed weather you use a bolt on or a "V" joint- best to you on your build  -- Peace, Donald

[Charlie Dunford]

Frank Ford,

 

I would like to hear what you have to say about this question. It would be much appreciated.

 

Charlie Dunford

 

[Charlie Dunford]

To Bill, Harrison and Donald, thanks for your responses to my question.  Its much appreciated.

I contacted a luthier who's knowledge of wood technology I respect. He recommended neck block grain running parallel to the grain of the sides and oriented so growth rings run fore and aft as you view the block from the side. Here is his reasoning:

- Wood shrinks most along the direction of the growth rings.  Minimize the length of the growth rings and you minimize that shrinkage.  Growth rings running fore and aft means 1.5 in long growth rings as opposed to 3 or 4 in long growth rings if you had the rings running up and down.

-  Wood has medullary rays that run perpendicular to the growh rings and they resist cracking parallel to the growth rings. In the neck block the rays would be running up and down and would resist cracking in the fore and aft direction, which is the short dimension of the block.  Wood splits easiest in the radial direction and that would be the long dimension of the block.

- When I expressed concern over differences of growth ring direction between the neck block and the neck in the dovetail joint he remimded me that mahogany has a low tangential to radial shrinkage ratio.  Thats why its a good instrument wood.  I looked it up in Bruce Hoadley's book "Understanding Wood" (page 74) .  The T/R ratio for mahogany is 1.4.  Most woods are closer to 2.  There are only a hand full of woods on his list that are lower than 1.4. Bottom line is mahogany is a very stable wood.

So there you have another opinion.  This makes a lot of sense to me. We will see how it works out.

Charlie Dunford