Base Circle

Base circle, abbreviated as BC, is a circle from where involute portion of tooth profile will be produced.

 

Base Circle formula
\(\large{ BC = PD \; cos\; PA }\)
Symbol	English	Metric
\(\large{ BC }\) = base circle	\(\large{in}\)	\(\large{mm}\)
\(\large{ PD }\) = pitch diameter	\(\large{in}\)	\(\large{mm}\)
\(\large{ PA }\) = pressure angle	\(\large{deg}\)	\(\large{rad}\)