The pinion is made of 3/8" brass with a hole drilled through the shrouds at something less than 3/32" in size. Then the hole was reamed with a commercial reamer which is 0.001" undersize. This permits an interference fit of the pinion shrouds on the arbor.
This reamer has proven in practice to be a bit tight -- when the fit is too tight, it's easy to bend small arbors when tapping home shrouds and collets. So I prefer to broach them a bit with a clockmaker's broach to a larger size. To make this rather foolproof, I have made lines on one of my broachs to indicate the extent of reaming. The lines were determined by test and practice.
The pins are made of 0.025" music wire. I cut them off with side cutters (ages those quickly to cut this material!) The ends are left protruding, then are ground off with a Dremel cut-off wheel, with the arbor chucked in the lathe and turing slowly. This makes a nice, smooth effect. Since these pinions are exposed in a skeleton clock, I also make small sheilds to fit over the ends of the arbors, thus capturing the pins and improving appearance. The shields are made in the same way as the shrouds themselves.
The contrate wheel collet is also made of 3/8" brass drilled to something less than 3/32", but it is reamed to full size with a homemade reamer, described in an earlier chapter. This collet is held onto the arbor with a tiny 0-80 Allen screw. A setscrew is used because the contrate must be adjusted to properly mesh with the pinion on the escape wheel. The setscrew makes it easy to make the adjustment with the wheels in the clock. I will later put a small flat on the contrate wheel arbor for the setscrew to seat into, which improves grip and also makes it easier to remove the wheel at a later time.
The contrate arbor is mounted between the frames by drilling pivot holes in the frames. This is done by disassembling the clock, and aligning the plates (frames) with two pins through the pillar holes. The holes are drilled through both frames in the same opporation, which guarantees alignment. The pins through the pillars was pictured in an earlier installment.
The contrate wheel meshes beautifully with the pinion on the escape wheel -- Good as the trannie in a Lexus -- a friend says.
Today's links:
Broach showing limit marks.
Pinion with wires unground.
Pinion on arbor finished
Finished contrate arbor.
Arbor in place.