Thickness Sander and Lattice Jig

I have given this some thought on and off over the holiday, between games with my granddaughter, and remembered something that was implicit in my design for the thickness sander all along, though I wasn't completely cognizant of it. The cross member that holds the hinge is not structural and was unintentionally, or perhaps intentionally behind the white noise that usually fills my head, set up to allow for adjustment. Consequently, I have resolved on the plan to withdraw the screws that hold the hinge support in place on the out-feed side. With the adjustment screw fully extended, I will then bring the hinge end of the platen up until it touches all the way across the drum, and screw the hinge support back into place. I've taken a straight edge to the drum, and it reasonably flat along its length all the way around its diameter, so to continue down my current path would simply distort the drum, making the radius smaller on one side than on the other. I will do this Saturday, when the kids and granddaughter return to Boise.

Also, in the meantime, I have been giving some thought to the first step in actually building the guitar, the plate joining for the soundboard and back. I have used the method that Sloane describes. After getting a good light-tight joint, on a work-board, one places a dowel or metal rod under the plates, taps nails along the two edges of the plates (not into the plates, but abutting them), removes the nails and presses the plates flat against the work-board, places a caul over the joint, and then weights that down. For weight, I used edger bricks wrapped in duct tape, but about anything suitably heavy would do. This works reasonably well -- that is to say, it works -- but I wouldn't necessarily recommend it. A couple of reasons, the most important being that you can't really see the joint as it is coming together and its difficult to get even pressure along the length of the joint with the caul, so there have been occasions where plates, perfectly thicknessed, have not come together sufficiently flat at the seam. I have had to cut them apart, re-joint the plates, and go through the steps again.

Consequently, I have been thinking about jigs to join the plates, and the one that holds the most promise is the lattice jig. I call it that for lack of a better term, but it is the jig sold by LMI. Though it has nice features, the price is a bit steep, and I think LMI, in particular, sets prices on such things as if to say, "look, if you're too lazy or impatient to build your own jigs, then you shouldn't be building guitars." Regardless, my next project will be the lattice jig. I will build it from birch ply, cutting strips about 2.5 inches in width and about 22 inches long. It will consist of basically two lattices (think a section rail road tracks with three ties) put together with interlocking notches. On the bottom lattice, on the ties, between the notches for the rails, I plan to remove about 3/8ths. This will accommodate 1/4 MDF and sheet plastic, that will provide a solid flat surface. On each end of the rails, I plan to drill three holes, large enough to thread rope. The three holes should provide enough friction to lock the rope in place, but if not, the exposed loop can be clamped to hold it. To use it, the plates are sandwiched between the two lattices, rope is crossed over the rails, locked into place, and then to provide clamping pressure, a wedge is tapped under the crossed ropes. The lattice holds the plates flat while the ropes provide pressure not only against the edges of the plates, but also to lattice. The trick to this will be keeping the lattice perfectly flat during construction.

A quarter sheet of birch ply should provide enough to build the lattice jig, with enough left over to build the jig that will build the radius dishes for sanding and gluing the braces on the sound board and backs.