Friday, April 3, 2009

Work that body! Body routs and neck attachment

Before I routed the bodies, I decided to make some new jigs. I laminate the different thicknesses of plywood needed from salvaged 1/4" Baltic Birch Board.

The new jigs are sweet. The PAF's fit with a little play, and the P-90 routs are just undersized for a final hand fit of the pickups. The bottom of the jig is sprayed with adhesive and allowed to dry. This makes for a non slip surface that won't stick permanently.

Once the pickup cavities are routed the bridge and stop tail piece bushing holes are located and drilled with the aid of a thick block jig. Of course the bushings are metric and my drill index, imperial, so I make the holes undersized and rasp them to fit. This is actually a good thing, as it makes for a very snug fit. The bushing are pressed into place after shellac and must stay put without adhesive.
The two sets of cross hairs on body and jig make for some very accurate hole placement.
But then again, we perform this check on the location mark about 50 times before we drill. Very nerve racking stuff, this. It will pay off with perfect intonation later on, though. Drilling for the grounding wire is a little tricky. I use a gouge to make a starting depression and to relieve the corner into the access hole in the instrument cavity.

Then with an extra long bit and a scrap of veneer to protect the top, the hole is made very carefully into the bridge bushing hole. Later we will route the grounding wire to be held in place by the bridge post bushing.
The instrument hole is bored with another jig, but not all the way through. A thin layer is left to support the waste and the knife finishes the cut cleanly.
The inside edge is cleaned up with a chainsaw file.The cavities for the P-90's are finished by hand for a perfect fit. Slightly undercut with the gouge and worked with the chainsaw file and that the covers just slip into place with the final sanding.At this point we can now veneer the back panels. These are cut to rough shape with the fret saw and scraped smooth at the seams. The bodies go back in the press for the last time as the backs are laminated in place.
The back panels are brought flush with the sides and the bodies are rounded over with the rasp.Starting with 60 grit the roundover is perfected and the edge is taken out throught the finer grits. The finish shaping of the body has to be done by hand as it is too easy to go right through the bindings with machine tools. There is something special about a hand shaped edge. To my eyes a machine shaped edge just won't do. It is, by no means, a quick and easy task, however.The holes in the neck plate are marked on the body and the holes drilled by hand. A scrap of ply is clamped in place to prevent tear out. Although most folks would expect to see a drill press here, I do not wish for the holes in the body to be at 90 degrees. In a process called draw boring, I angle the holes just slightly to direct the clamping pressure of the screws and draw the neck into the mortise.Note how the exit hole is at the top inside limit of the neck plate layout line. When screwed tight the neck will be drawn into the mortise. Not that there is slack to fill, but the whole assembly is just all that much more secure.With the neck clamped in place the screw holes are drilled. Because the drill bit for the threaded portion of the hole is smaller than the shank hole in the body there is a bit of play when starting the hole in the neck. This is put to use, positioning it at the top, to further increase the draw effect. Once started the bit is kept perpendicular to the neck line at the mortise.With the neck bolted on the contours of the join are finished carved and sanded smooth. At this point things are starting to look pretty good. If you only knew how far they yet have to go....

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