This tutorial demonstrates a method of constructing an intersection point between an arc and a line. Sometimes a print will call out a dimension to a tangent. If you try to construct an intersection between an arc and a line directly, usually the arc will intersect the line in two points very close together, or not at all. This technique, on the other hand, works every time and is based on a rule of geometry that the tangent point will always form a perpendicular angle between the line and the center of the arc.
Holco Metrology Solutions