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April 07, 2020
The simplest and most efficient way to glue-up an acoustic guitar or classical guitar neck is to use the Georgia Luthier Supply Neck Assembly Jig. Using this jig you can cut your neck blanks to size, cut the scarf joint very accurately, and glue the headpiece and the heel blocks at the same time.
A bit of background needs to be addressed. To give a guitar neck the ultimate in strength and bending resistance please review our articles on static neck reinforcement, properties of wood in neck construction, and adjustable truss rods.
Since wood for guitar necks tends to be quite costly, and if you are new to guitar construction, it may be a good idea for to follow this procedure with a scrap piece of wood rather than ruining a $25 piece of neck stock. Upon mastering the process feel free to start using the jig for production.
In order to get the most out of the neck stock, square up the piece of neck stock before the start the construction process. Usually a piece of neck stock will measure about 3” x 36” x 7/8” thick (75mm x 900mm x 22mm). Place the entire length of neck stock into the jig if possible with the head block end of the neck tightly against the end closure of the jig. Clamp the neck stock in place with a couple of quick-release clamps, or Bessey Clamps check that the bottom of the stock is flat against the jig floor.
Install the miter slot guide bar to the bottom of the Neck Jig with the 3 Free Spinning Knobs and run the Neck Jig slowly through the band saw. Keep the feed rate slow and consistent with only forward force and no sideways pressure. The quality of the scarf joint will only be as good as the band saw setup, Also double check the blade tension. (Note: if you wish to construct a laminated wood neck - see the instructions that follow this section).
Upon making the scarf joint cut, the head piece needs to be cut to length. First mark out the thickness of the headpiece on the cutoff you just removed from the jig. When you determine the proper headpiece length, cut the headpiece from the cutoff wood. Next cut the headpiece to the proper thickness using a band saw. Finish sand the headpiece surfaces as needed.
Even though the saw-cut from the band saw may be very smooth, it does need to be sanded smooth for a proper glue joint as this joint receives a lot of prying force from the strings. I choose to do this on a stationary belt sander, but it can easily be completed on a large sanding surface as well, such as a piece of marble or corian countertop with adhesive sandpaper attached to the surface.
With the neck stock still loaded in the jig, insert the headpiece into the jig with the angled face of the cut facing up toward the fence. Mount the heel block retainer in place and cut the heel blocks to length from the cutoff portion of the headpiece. Note that there is one of the heel blocks that is longer and that piece is mounted directly to underside of the neck.
Size and glue your headpiece veneer sandwich, if you are going to add that detail to your guitar. There are many options that you can use to add this very attractive detail to your handmade guitar.
If all looks well, glue all blocks in place using the clamping cauls to prevent denting of the stock. Note that is is a good idea to place waxed paper beneath the neck prior to gluing to minimize cleanup and damage to the jig.
In order to obtain the best and most warp resistant neck construction, arrange the neck wood so each half of the neck grain of each half of the neck stock runs in opposite directions (refer to illustration). By doing this we are using the properties of woods' ability to shrink and contract and have these forces create an even stronger, more warp-resistant neck than is attainable with a single-piece vertical piece of wood. I have always constructed my necks this way and have experienced very few problems with warping.
(Note: to have the laminations run continuously from the neck into the headpiece, complete this task prior to cutting the scarf joint in order to best align the laminations.) Also, to keep things aligned, cut each half of the neck wood exactly the same width. This will make it easy to line up the laminated wood pieces in the Neck Assembly Jig.
I prefer to use a table saw for this operation. To obtain this grain pattern you will have to flip one of the pieces of neck stock 180 degree. This is most easily done by looking at the freshly cut end grain. Finally cut the center strip or or
Glue all the wood lamentation together as shown in the diagram. After the neck laminations are dry, square-up all sides and sand smooth. Lastly, the neck width has to match the width of the original wood blank (about 3”). Measure the difference in width from the laminated neck and the remainder of the headstock and split the difference. Cut this amount from each side of the neck to match them up correctly.
Use plywood clamping cauls to protect the neck wood from denting during clamping. Place the laminated neck into the Neck Assembly Jig and cut the scarf joint. Remove the neck and sand the scarf joint on a stationary belt sander or smooth with a hand plane or sanding surfaces. Continue to assemble the neck as per the one-piece neck construction above.
Now that the neck has been squared up, it is time to channel the neck to prepare it for reinforcing. There are many options available to the luthier and we cover many of them in this blog. By keep the neck consistently square you can easily use a shaper or a router or even a tablesaw to cut the required channeling.
Now that the reinforcing has been installed and the surface of the neck has been leveled, it is time to install the headpiece veneer. My reinforcement of choice is Aircraft Aluminum, or T6 tempered aluminum. This is tough stuff and when it is epoxied into the center of your neck combined with the wood lamination that we talked about earlier in this article, you will have a neck that is hard to beat. For this reinforcement, be sure to visit our Aluminum Neck Reinforcement Product Page so you can use the same superior reinforcement that is used in all of my necks.
The uppermost headpiece veneer should be approx. 1/16" thick (1.5mm). This veneer more often than not matches the hardwood of the guitar back and sides, but occasionally it can be a feature veneer such as curly or bird’s eye Maple, Ebony, or other exotic wood species.
Additionally you can choose to build up several layers of alternating light and dark veneers giving a very nice layered look, and this can match the purfling of the fretboard or the guitar top/side binding.
Another alternative is to trim the headpiece with either wood or plastic purfling by cutting a small channel with a dermal router after the veneers have been laminated and trimmed to the headpiece.
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