Making pallets for a deadbeat escapement requires you to grind the faces of the pallets to size. The outer arc of the faces of the pallets is fairly easy to grind, but the inner one is not. Here's a lathe fixture which makes it possible to grind both the inner and outer arc of the pallets with great accuracy. The lathe is a Taig Micro.
Here we see the pallets being ground -- the outside arc on the left and the inside arc on the right. The pallets are held in a pallet arbor which slips over a special post on the lathe carriage. The arbor can be turned back and forth to make the grind.
What's special here is that the arbor can be inverted. Once a grind is made on one face, the arbor can be inverted on its post to grind the same face on the other pallet -- all without changing the settings of the lathe. The pallet faces are thus ground uniformly.
The grinding wheel is made from three Dremel cutoff wheels (Dremel part number 409) which are screwed onto the same arbor. The edge of the wheel is angled to make it easier to grind the insides of the pallets.
The inside of the pallet is ground with the outer edge of the grinding wheel. There is a little angle between the wheel and the pallet which should be kept small by adjusting the lathe carriage and cross feed. The pallet will be slightly hollow-ground, which does no harm. Run the lathe as fast as it will go.
The pallet arbor is made in two parts, which screw together through the hole in the pallets.
Each half of the arbor has a 1/4" hole in the end to make inversion possible.
The pallet arbor holes slip over a 1/4" post which is screwed to the lathe carriage. The fit between the post and the hole in the arbor must be quite close.
The pallet arbor can also be used in a homemade depthing tool. The escape wheel to be fitted is mounted on its own arbor. The brass leg on the depthing tool is adjustable. This way, the impulse angles on the tips of the pallets can be measured, ground and tested in the depthing tool until it's all just right.
Once the correct depth between pallets and wheel is ascertained, the points on the depthing tool posts can be used to mark plates with the correct spacing.
