To make the spine, I take the two strips of metal, stack them in the vise, drill the 8-32 (#29) pilot hole though both, run the tap part way the top strip (holding it in the drill chuck so it is perpendicular to the strip), then split them and finish the tapping the top plate. The other plate is drilled with the body drill (#18) and counter sunk. Now the two strips can be screwed together and I can drill and tap the rest of the holes without worrying that the stripes will become misaligned. After that, the strips are again separated, finish tapped and the other strip is counter bored.
- If you are using same piece of metal for both strips, flip and twist one of the strips so that, when pressed together, any warps will cancel out.
- This stuff is never the same width, no mater what the package claims. So one of the strips is going to be clamped tighter than than the other, which is why I do one screw first, to act as a index/holder, before drilling the rest of the holes.
- Things never turn out perfect so I screw the spine together and buzz it off in the mill to square it up. A file would work just as well.
- In the photo, I haven’t punched holes in the saw plate so the spine is just clamping top of the plate. When done, all three will be at the same level.