shaping the neck

Last episode, I finished shaping the tin. For part three of how it’s made I’ll give some details of cutting and shaping the maple neck and its extension through the tin. This won’t include the fret board. That will have to wait for another episode. Even without the fret board this may be a bit long, so hold on to yer hats’n glasses! After the initial work on the band saw, table saw, and drill press this is all hand work with rasps, chisels, and sand paper. Apologies for the sharp focus on the backgrounds. One day I’ll learn to force a digital camera to focus where I want it.

neck shape 2Following the measured drawing I made way back when I planned the instrument around a particular tin, I transfer all the measurements to a plank of maple. This picture shows a neck after a rough cut on the band saw, holes drilled for tuning machines and the strap, some lengthwise cuts to narrow the head and tail, and some initial profile smoothing with the rasps. Those holes were drilled before the lengthwise trim cuts were made. The drill press makes them nice and square and tear-out is eliminated when the waste pieces are removed. Some center lines in pencil are visible here. After squaring up the neck blank and all this early work I replace any guide marks that have been cut away.

neck shape 3This is looking at the butt end of the neck where it will someday meet the tin. The brighter part in the foreground is the extension of the neck that passes all the way through the center of the tin to the string anchor at the tail. This one piece neck and extension take all the string tension. You can see the pencil line marking the intended taper where the neck will join the tin. I like to get this taper set up before shaping the middle of the neck. This sets a limit on the curve of the middle section.

neck shape 4Above is one side tapered to meet my guide marks. I’ll flip the piece over and do the other side right away. I like to take small bites on each side while checking the symmetry at every step.

Now to get my head straight. This work will help set limits on the curve of the center part of the neck too.

neck shape 5I have already trimmed the waste piece off the other side of the head. The table saw cut is set a bit wider than the finished head. I’ll have to do quite a bit of work to smooth and clean up what the table saw leaves behind.

neck shape 7Time to clean the gum off the saw blade. It got a bit hot and left some burn marks.

neck shape 8after grinding with the rat tail rasp.

neck shape 9after some chisel work to make one flush surface…

neck shape 10and several grades of sandpaper later, the head and the curve leading to the middle section of the neck are well roughed out.

neck shape 11The center section is still a tapered block itching for some relief, but first lets freshen up those guide marks.

neck shape 16If you’re not familiar with the tool pictured above, you’re missing out. It’s one of the best tools ever, a carpenter’s scribe, and I depend on it for making guide lines that are parallel to this or that edge. The tiny black rod at the Left end is a piece of graphite pencil “lead” set so it can be inched down as it wears out. That’s a thumbscrew sticking out of the block. It locks the block in any position along the roughly graduated stick.

neck shape 14Scribe in action!… marking a center line…

neck shape 15and marking a pair of “don’t cut anymore!” warning lines along the edge where the fret board will join. When the uppermost of these lines gets faint or disappears I know my curve is getting close to removing wood that I want to keep on the edge.

neck shape 17Next, I check that center line with a short straight edge and back-light. I want the center line to fit nice and tight on that straight edge. The light getting under the straight edge indicates low spots and the dark shows high spots. Hmm… needs work. I will rasp and sand carefully until I see very little light getting through, and finish by redrawing my center line.

OK, last part of this post, I swear.

neck shape 18For this bit, I like to clamp the neck to a beam that sticks out from my bench. This makes it easy to work both sides of the middle section for a uniform result.

neck shape 20This is the first of MANY cuts to make nice even facets roughing out the curved cross section of the center of the neck. Each added facet gets narrower and closer to a smooth curve as I work. Note that everything must cope with the taper from head to tail…. lots of standing back with chin scratching is in order here.

neck shape 21After making all these swell, even spaced, symmetrical facets now I must destroy them. Back in the bench vise, with raking light from my faithful swivel lamp, I look carefully for the edges of those facets, and eliminate them one by one with many grades of sand paper. Blue lines in the inset image highlight the edges of several facets visible in the photo. All these have gotta go. In addition, if you look close at the inset (you can click on the image for a closer look) there are two green arrows indicating that my “don’t cut anymore” lines are indeed still there.

neck shape 22This is getting close to a smooth curve. The raking light still shows some work to be done. I find that taking the neck out into sunlight and watching as I roll the piece in and out of shadow will point out the flaws. Curves, man… they’re finicky!

Next time, joining neck to tin. Buon legno!