Today I finished the motion work train. I cut the minute pinion from the pinion stick, but not until I had drilled it with a 1/8" hole and had cut a shoulder on it. This shoulder cut fits into the 3/16" hole in the minute wheel. It was made an interference fit, so that no solder is necessary.

The cannon pinion was simlarly fit with a disk, which will provide a place for a small leaf spring to press. The inside of this spring presses against an E-clip which rides in a groove already cut in the 3/32" center arbor/handshaft. This forms the hand clutch.

I had inteneded to fasten the minute wheel and post to the frame with a shoulder screw -- but after the screw was finished, I managed to twist the screw off in the plate. The threads on the screw were cut with a split die and were too tight. The die should have been clamped to tighten it and make deeper threads. Instead, I put the minute wheel on a post with a screw-on base. It turned out well.

I cut the post base from 1/2" brass, cutting a spigot on one end which will set the minute wheel and its pinion the proper distance away from the frame. The center hole in the base was drilled less than 1/8" and then reamed to .001" under an eighth using a one-under reamer. The post is made of 1/8" drill rod which is tap-fit into the hole. I also drilled a small transverse hole in the 1/8" post for a keeper pin which will hold on the minute wheel and a terminal washer. The base was drilled with 2 small holes which will hold 1-72 mounting screws.

The entire motion work, consisting of the minute wheel, the hour pipe and the cannon pinion were mounted on temporary arbors in the Webster depthing tool to test out. It's important that the the gears mesh properly and function smoothly. Had I not botched the shoulder screw, the distance measured by the depthing tool would have been transferred to the frame and used to detemine the location of the shoulder screw on the frame.

Instead, I placed the based post on the frame, installed the gears, adjusted the mesh, and carefully held the post in place in the proper position. Then I clamped it with Super Glue by placing a drop next to the edge, allowing it to wick under the post.

After the glue set, I checked to be sure that the motion work train worked smoothly, then started holes in the frames using the same size drill I had used to drill the holes in the base of the post -- this to accurately set the position of the holes. Then I switched drills to the correct size for a 1-72 tap and drilled the holes through. The post required a small amount of heat to break it loose from the frame. (If this was a hazardous practice, I would have been dead years ago.)

It's tense work tapping small holes in brass -- especially deep ones. A tap can break easily, leaving more excess steel lodged in the frames. I always attempt to screw the tap in slowly, making sure it's held vertical, since many small taps are broken by being fed into holes at even a slight slant. I also use a pin vise to hold the tap, as it's more sensitive to the touch than a T-handle, and you're less apt to wobble or use excess force. I use a synthetic oil as a lube, make cuts of only about 1/4 to 1/2 turn before reversing to clear chips. I frequently remove the tap and blow it off with compressed air, or use a toothbrush to clean off chips.

The hand clutch tension spring is made of .003" blue suspension spring steel. The 3/32" hole is made with a punch made from 3/32" drill rod, hardened on one end and ground sharp and flat. The spring material is layed on a block of lead which forms the die, and the punch is given a smart rap with a small hammer. The spring is cut to size with ordinary scissors, then shaped with a 1" belt sander. The angles on it were bent with duck-bill pliers.

When the dial is made, I can determine the correct length for the handshaft. At that point, the end of the shaft will either be reduced in size and threaded for a hand nut, or a hole will be drilled in the handshaft for a retaining pin. This will press the assembly against the clutch spring, forming the hand clutch.

I also began dial-making by cutting a 3.5" circle out of paper to slip over the new handshaft. This to see if the dial will clear the dome and the winding arbor below it. Next will be the dial support bracket and the dial itself.

Cannon pinion with disk.
Minute wheel and post.
Minute wheel and post II.
In depthing tool.
Drilling minute wheel post.
Post on frame with glue.
Tapping post screw holes.
Motion work together.
Hand clutch spring.
Dial test.