The clocks rate is regulated by a moveable foot. The foot has a narrow slit in it (0.002 wide) which, during adjustment, slides up or down along the flat balance suspension spring. This effectively lengthens or shortens the suspension spring and changes the clocks rate.
The top of the foot shaft is threaded, with a knurled adjusting nut atop -- turning the knob moves the foot. In addition, the foot slides on a 1/16" rod, to provide stability.
The foot is begun by sawing a slit in a block of 3/16" flat brass clamped in the Taig mill, using a circular saw. After the slit is made, a compression hole is drilled at the inner end of it. This hole's role is to thin the brass at that point, to allow some bending there.
The saw slit is .010" thick, which is much too thick for the suspension spring used. Once the hole is drilled, the slit can be narrowed by compressing the block between the jaws of a large vice -- with the corner of the vice jaws at the level of the hole in the foot block. There is some spring to the brass, which means that the slit doesn't quite close after compression -- in fact, the slit measures .002" wide, using an automotive thickness gage. Just what's need.
Then another hole is drilled behind the compression hole. This hole is a bit less than 3/32", so that the foot shaft can be friction-fitted into the hole. The shaft is 3/32" in diameter, and a reduced diameter with a slight taper is made on one end of it. The easiest way to do this is to use a graver and a watchmakers lathe.
Then the foot is separated from the mother block by sawing it away with a jeweler's saw, and the foot shaft is friction fit (tapped) into its hole.
At this point, the foot shaft is slipped into the proper hole in the regulator block made last chapter, and the foot is clamped in place on the block with Super Glue. This maintains exact alignment between the foot and the regulator block, so that a 1/16" hole can be drilled through the bottom of the foot and into the bottom of the regulator block. This will serve to mount a piece of 1/16" music wire which will act as a guide for the foot. The wire is secured in the bottom of the regulator block with Loctite. The foot slides up and down on this guide
The results are very good -- the foot slides up and down in the regulator block with ease. I'll add the threads at the top of the foot shaft later, when I know how long the foot must extend below the regulator block to achieve regulation. At that time, I'll also shorten the 1/16" guide rod.
Todays' links:
Sawing slit
Mother block 1
Mother block 2
Compressing slit
Regulator block glued on mother block
Slit gauged
Foot 1
Foot 2
Regulator complete
Regulator, GIF
Downloads: