Today I finished making the legs. After sawing out, they were finished by draw-filing the edges, then by using 600,1200 and 1500 grit silicon carbide sandpaper, and then by burnishing with 0000 steel wool.
The location of the screw mounting holes on the legs is important, so the place of the holes was determined by using a simple jig. A 1/4" wooden dowel was glued into a 1/4" hole in a board, over which were inserted the legs through the pillar holes. Then marks were made using a ruler and fine marker.
Usually, I make marks which must be centered in the middle of something by using a dial caliper. The caliper is set to half of the thickness (half of 3/16" in the case of the legs) and one leg of the caliper is used to make a scratch in the subject material, using the other leg as a guide. To be really accurate, repeat the procedure, using the other side of the material as a guide. This leaves a line in the exact center of the material. Then another line is made at right angles, indicating with "cross hairs" where the hole will go.
Then, I use the point of a scratch awl to find the point at which the scratched lines intersect (you can do this better by feel, but a loupe is handy, too) and make a sharp little pointed mark by pushing, not hammering. Once this is in the right spot, it is enlarged with a center punch and light hammer taps to a size which will center the drill. You can also use a spotting drill. Visibility of scratched lines is much enhanced by using layout fluid (Dykem).
The holes were drilled to a size for 4-40 screws. The bottom leg mounting holes must be made into slots with a jewelers saw and file, since the angle of the leg itself prohibits insertion of a screw into the hole. (The screw will first screwed part way into the frame before the leg is installed.)
Before screwing the legs to the frames, it is important to get them set at the right heigth. There must be room below for the swinging pendulum to clear the base, and there must be room above the movement to clear the dome top. To be sure, the approximate position of the legs on the frames was first estimated, then the legs were "clamped" onto the frames using Super Glue. When all was well, the leg screw mounting holes were made in the frames themselves.
The mounting holes in the frames are made by first drilling the top leg holes in the center of the 1/4" frame material, using the marking method described above. Then they are tapped, and the legs are screwed on. Then the position of the bottom hole on the frame is marked, drilled, and tapped.
The leg pillars are made the same way as the main pillars, already constructed. However, since they are slightly longer, they are made distinct from the other pillars by using two small decorative center lines instead of one. The leg pillars are slightly longer because 3/16" leg material is screwed to 1/4" frame material, and there is a 1/32" offset.
The only things left to construct are the little train of gears which drive the hands, and the dial and hands....and a lot of polishing.
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