Details on building the escapement for this clock were pretty thin earlier, so I decided to build and document another set of pallets and some more escape wheels which I'll use in later clocks.

I sawed the previous escape wheel teeth with a 0.010" thick by 1" in diameter slitting saw. While this worked well, I decided to cut the new wheels with a flycutter. The only advantage here is that the flycutter can create rounded backs on the escape wheel teeth. This permits a little more pallet clearance, and also looks more traditional. The flycutter was made to fit into an existing flycutter arbor which fits into a 3/16" collet in the Sherline mill.

The flycutter blank was first slit lengthwise to form the cutting surface, then ground with a 3/4" radius, which forms the curve on the backs of the teeth. The curve was ground on the back of the cutter with a bench grinder, and the proper curve was achieved by comparison with a 3/4" radius circle drawn on paper. This curve must also have a slight angle on the back of it to provide clearance, like a lathe bit. The straight edge of the cutter is also sloped back to provide clearance. Then the cutter was hardened and tempered. All-in-all, it's a fairly complicated operation to make this cutter.

The crown wheel blank (made as previously described) was mounted on the Sherline rotary table with a special mandrel. This mandrel has 3/8" threads which screw into the thread in the center of the rotary table. It is 1/4" thick above, to match the size of the hole in the center of the wheel blanks. The 45-tooth wheel was cut by indexing the rotary table 8 degrees for each tooth.

The pallets are made from 3/64" gauge plate. The blank is cut so that it's just long enough to extend above the top of a board which has a 45-degree angle cut on it -- the angle of the lifting surfaces on the pallets. The part of the pallets which contain the nibs is cut out first, and the blank is screwed onto the 45-degree angle face of the board. The angles on the nibs are then filed and ground on the nibs, using a roller which is actually a drill bit. The bit holds one end of a file or stone, and is the same thickness as the nibs are high off the top of the board.

The angles on the nibs fall in opposite directions, so one side must be done at a time, turning the nibs over on the board to do the second angle on the second nib. It's possible to slope the nibs in the wrong direction, so consider the direction the escape wheel will turn before beginning to file the slopes.

The lifting surfaces of the nibs are polished, since this is the best time to do that. Then, the rest of the pallets are sawed away from the blank.

Links:

Flycutter blank and arbor.
Flycutter(1)
Flycutter(2)
Grinding curve on flycutter.
Flycutter finished.
Cutting crown wheel.
Crown wheel cut.
Rotary table mandrel.
Table with mandrel.
Pallet blank.
Board with blank and roller.
Grinding pallet lifting surface.
New wheel and pallets.