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How to Heat Treat Clock Pinions

A pinion is the smaller of two engaged gears. Pinions are often mounted to or machined into a shaft, so the larger gear is in turn turning the shaft. Clocks employ a number of pinions. Clock pinions are made from a variety of metals from brass to steel to alloy steels such as stainless. Heat treating a clock pinion depends upon the kind of metal you use. Clock components don't require a lot of strength, but the continual friction does benefit from hardness.

Things You'll Need

Small iron pot and lid
Sand
Oven
Oven mitt
Thermometer
Clock

Instructions

- 1
  Preheat a crucible-like iron container filled with sand. Place the pinion in the sand, then cover with a cast iron lid. The pinion should be supported so it is not laying on its side, for example, but situated vertically to help it heat and cool evenly. No part should be touching the metal sides. It should be suspended in the sand.
- 2
  Place the preheated, cast iron container in an evenly heated oven at 350 to 375 degrees Fahrenheit. Make sure the container is placed in the oven so that there are no hot sides or cool sides in the oven; the heat must be even.
- 3
  "Soak" the part in the oven, keeping it heated to a constant temperature for nine to 24 hours. Make sure the temperature does not fluctuate. To monitor the heat, use an internal thermometer you can see without opening the oven. With such a delicate part, cool air from one side of the part can cause significant deformity.
- 4
  Turn the oven off after the soaking period and let it cool on its own without opening the door for one hour or so.
- 5
  Leave the part to cool in the oven or, after it has cooled considerably, move the cast iron container to a cooling station to cool the rest of the way.
- 6
  When the container is completely cool to the touch, you can remove the lid and the pinion which has now been "precipitation heated." It's a cost-effective way to heat delicate parts without warping them.

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