Sprockets chain sprocket

[pianoman8t8]

Does anyone know what the bolt circle dia or radius is for the 9 hole pattern chain sprocket? like if i found center of the sprocket, and i wanted to go out the radius of the circle, which would put me dead-center of one of the 9 holes in the sprocket. Does this make any sense to any one?

 

[etheric]

You got it right, it's generally refered to as BCD, Bolt Circle Diameter.
Sorry, I don't know off hand.