A-Z glossary

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Pitch Circle

Where two GEARWHEELS are running together, each is considered to have an imaginary circle, these circles just touch each other at the point of nearest approach of the wheels. The diameters of these Pitch Circles are such that if the wheels had no TEETH and the pitch circles were pressed together so that they did not slip, the relative motions of the two wheels would be the same as with toothed wheels. Pitch Circles are usually marked out on the ends of wooden COGS when laying out the shapes and positions for their working faces.