Classic-guitar neckblank machining sequence (Part Two)
I have actually allowed a small amount of material to overhang the fourth line so I can then table-saw the rear surface of the blank smooth and flush. I then continue the centerline and the third line around the block as shown.
I've created a heel template out of cardboard and used it to mark the heelblock, as shown.
A 1/4-inch, 6 tooth per inch bandsaw blade performs the cut perfectly. Note the small "step" I've allowed at the end of the cut, for security's sake. If i were to inadvertently cut into the shaft, I could ruin the entire neckblank.
I will proceed to shape the heel on the table saw. At the foot of the heelblock, I've marked the desired width of my heel cap. The blade is raised until the top tooth just grazes the limit line of the heel cap. NOTE: The following table-saw shaping sequence will not work unless you have a saw blade that is 10-inches (25.4 cm or its closest partner) in diameter with brazed-on carbide tips like the one shown above. Ordinary high-speed steel circular saw blades with tips cut into the disk will not cut the wood in the way that is required by this technique.
Then the miter fence is pushed another 3/32 inch or so towards the blade--the workpiece advancing towards the blade accordingly--and then slid horizontally across the spinning blade until it reaches the root of the heelcap. Bit by bit, the miter fence with the work piece is advanced, each time shaving a curved swath out of the work piece at the set cut height. When the blade finally approaches the bottom of the shaft, start your cut about two inches beyond the beginning of the curved portion of the heelblock. Then continue advancing and sliding the workpiece from that point, advancing into the blade until the cut almost reaches the opposite surface of the neckshaft, but coming up just about 1/8 inch shy of touching it.
Another view of the planer cut.
The miter fence is now placed in the slot in the table opposite to its original location, and the blade now addresses the opposite side of the heelblock. The opposite side of the heel is now planed away in the same manner as the first. You can see clearly the result of the earlier shaping step, and see how it stops just 1/8" shy of the top surface of the neck shaft. The cut has produced an elegant, sweeping shape. The resulting projecting portion of the headblock is burned and scarred from repeatedly being pressed into the side of the blade, but this will be cleanly cut away during the subsequent slotting steps. In the photo, don't mistake the mahogany miter-fence extension bar for part of the neck!
A graceful, symmetrical heel shape emerges. Shaping the interior headblock and slotting is next.
The headblock is tapered on the bandsaw. This can be done if your bandsaw table can tip in both directions, such as my 14" Rockwell-Delta can. I've tipped the table to enable the blade to follow a pencil line on the back of the headblock than connects the maximum width of the headblock at the top of the shaft to the minimum width of the headblock at it's bottom. NOTE: Make sure that the total resulting maximum width of the headblock is wider than the desired width of your fingerboard at the 12th fret! My total headblock width at the top (i.e, the face that you glue to the soundboard) is 2 5/8-inches (66.5mm)
The angled bandsaw cut starts at the headblock and extends down the shaft and stops just shy of the verge of the headpiece. Do not follow the cut into the headpiece. Instead pull the workpiece back through the original cut to remove the workpiece from the saw.
The opposite angle cut is done in the mirror-opposite fashion, this time on the bandsaw table that has been slanted in the opposite direction to the first--and the fence readjusted appropriately. The long, slender scrap portion left hanging can be trimmed away or broken off by hand.