Planing a KingWay Straight Edge

I have machined half a dozen of these "King Way" straight edges, and even though I had spent considerable time planing a new and different setup procedure for each one, I had never felt the setup was a good one - always a snag somewhere so that the job did not go as planned. However, this time it seemed like the setup might work. Confident that this might be so, I took photographs and some video. I decided to post the result so others could see the principles and better them. It is 36" long. The raw casting contains a small step at the base of the angled surface. I started by cutting that small narrow step, or land, the length of the straight edge. This land is machined with a square shoulder. If necessary, the corner should be relieved to accept the corner of your parallels. This cut will define the longitudinal axis, and will be used to align the part to create the three planes of the straight edge. The cut will also be used to support cutting forces. Note the setup for cutting this land. The part is supported on the table in just three places: under the thick edge by two 1/8" shims; and in the back by a wedge. The wedge is used to level the part. In the other plane, the part is held against two slot-blocks by two stop pins, placement of which line up with the bracing columns of the straight edge. The setup insures that the part is reasonably at rest and the land will be used to define the three planes for the rest of the operation. Next, after cutting the land, the part is flipped and the just-cut land is set up on two parallels. These parallels are aligned by pressing up against two slot-blocks. The dangling thin edge of the part is supported as before by using a wedge to adjust the height for level. Clamps are placed at each end of the part, pressing the land down against the parallels. The stops at each end are angled inward a bit so that some of their force is used to hold the part (and parallels, and spacer blocks) up against the slot-blocks for alignment. The top surface and the side were then cut. Roughing feed rates were 0.060", 0.030" for finish. In the video I show the parallels after the cutting was completed, not before as the order indicates. To cut the angled surface the part was flipped so that the just-cut top surface rests against the table, and the just-cut vertical is up against slot-blocks. As before, a wedge is used to level the part, this time by using a square against the vertical surface. One clamp is used over the wedge, and the end-stops use "fingers" to hold the rest of the part down. Two stops are used to press the part crosswise against the slot-blocks. Note that a 0.003" shim was necessary at the center of the part to account for either stress removal during cutting, or perhaps an inaccurate previous setup. The angled surface is roughed at a 0.060" feed rate and finished at a 0.030" rate. Before breaking the setup, the initial narrow land is re-cut to account for any warping. Further, I cut a small 0.030" flat on the knife edge, both to break the fragile edge, and to record the state of straight edge in that axis when the angle was cut. After breaking the setup, comparing this to the table will easily show straightness in this axis. Finally, the surfaces are checked. It is expected that each will need a finish cut and they are cut in the same manner as in the roughing cuts. In this case, only the surface that required the shimming needed re-cutting, and I skipped the parallels and set the 0.030" edge directly against the table and the base pressed against slot-blocks. The setups were easy and uncomplicated, and the part allowed to be at rest. This is the first time I have cut one of these that I was not disappointed with the setup. Still room for improvement, though: for example the angled stop-pins directing some of the force to the slot-blocks could be a bit awkward if the part were a different length than this one. -Rees