What is a thing to be added; an appendix or addition. Addendum circle (Mech.), the circle which may be described around a circular spur wheel or gear wheel, touching the crests or tips of the teeth. Rankine called?

addendum — A thing to be added; an appendix or addition. Addendum circle (Mech.), the circle which may be described around a circular spur wheel or gear wheel, touching the crests or tips of the teeth. Rankine. (Webster's 1913.)

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