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Today I made hands for the new clock. They're made from .015" steel shim stock, blued and colleted. Finishing the hands makes it possible to finish the clock's motion work, as well.
I drafted the hands to scale in Deltacad, printed the template, and glued it to the mother steel in familiar fashion. Before sawing out the hands, I drilled the hand holes in the mother material, since it's much easier to drill holes in larger pieces. The material is thin, so I used a step drill called a "Unibit" to make the holes. It makes clean, round holes in thin material. You can't drill large holes in thin material with a conventional drill bit.
Since the hands are small and delicate, I made a new block made for sawing small parts. The block is simply a piece of wood with a 1/4" hole drilled through, with a slit cut to the hole for blade access. Such a block makes sawing small, delicate parts much easier.
Tiny, delicate parts are also difficult to finish, so I tried using two-sided sticky tape to stick down the hand to a piece of wood. With a hand held firmly by the tape, its easy to use abrasive paper buff sticks to polish it. When the hands had a good finish, I cleaned them thoroughly and blued them with a heat gun. The two-sided tape used is a quality tape, not the stuff used to hold down carpet.
I also made collets for the hands. A collet is simply a ring with a flange, with the hand rivetted on the flange. The collets have 0-80 set screws, to hold them to the hand shafts.
I put the motion work with the hour and minute hand shafts and the hand clutch spring on the front plate, then put the dial on the front plate as well. With everything in place, I marked the hand shafts at the correct length and shortened them. I also made a retaining collar for the end of the minute hand shaft, which holds the whole assembly together. It's also retained on the minute hand shaft with a 0-80 set screw.
The clock is nearing completion, so I'm also finishing up some things left undone earlier. I made a pawl for the maintaining ratchet, which I made from a piece of brass that underwent some "brass-smithing". The end of the pawl must engage with the teeth on the maintaining ratchet, but the brass is only 1/16" wide. So, to be certain that it would always engage, I used a small hammer to flatten and widen the end, curving it at the same time.
I hammered it over the horn of a small anvil to make it both wider and curved. Brass becomes brittle (work-hardened) when hammered too much, so I annealed the end of the pawl several time with a propane torch. Unlike steel, you hammer brass cold, then heat it red hot to remove work stress. I did the finish work with files.
The pawl has a circular weight on on the opposite end, to keep the tip pressed against the teeth of the maintaining ratchet. I'll make an arbor for the pawl when I put the plates back together.
I'm also beginning to do final finishing on the clock. This time, I'm trying out the concept of a "finishing box" which will permit sanding the plate with a finishing sander without rounding over the edges of the plate. To make the box, I layed the plate on a piece of common plexiglass, marked around it, and then sawed the shape out of the plastic. This leaves a pocket in the plastic with the same shape as the plate. I then screwed the plastic "box" to a board. Then you can hold the plate firmly in the box and sand it with progressively finer wet-and-dry sandpaper.
The rivetting hammer is a small, inexpensive little hammer that I've found to be great for rivetting jobs. One end of the head is flat, the other is chisel-shaped. This hammer is smaller and lighter than most hammers, making small, quick blows, and it cost only a couple of dollars.
Today's links:
Hands and step drill
Sawing hands
Sawing block
Hands sawed
Hands on 2-side tape
Hands blued
Motion work trimmed
Dial with hands
Maintaining pawl
Pawl tip
Finishing box
Rivetting hammer