Base Circle

Tags:
Gear

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

Base circle, abbreviated as BC, is a circle from where involute portion of tooth profile will be produced. The base circle of a gear is an important concept in gear geometry. It is a theoretical circle that is used as a reference in the design of involute gears. The base circle is defined as the circle from which the involute curve of the gear tooth is generated.