Technical Drawing - Interpenetration - Introduction

When two soids interpenetrate, (intersect), eachother a straight line or a curved line of interpenetration is formed.  Whether the line is curved or straight depends on the shape of the solids.

Flat  --  Flat  =  Straight

Flat  --  Curved  =  Curved

Curved  --  Curved  =  Curved

To find the lines of interpenetration we find points that both solids have in common and join them together.  For flat surfaced solids the easiest way of doing this is to use the corners of the solid.  In the case of curved surfaces we break the curve into sections using generators.  We pretend these generators are edges.

A Generator is an imaginary line drawn along the surface of a curved solid which if rotated around the axis of the solid follows the path of the curved surface.
Cone with Generator
In order to draw lines of interpenetration you always need the Elevation and Plan and usually an End View.  For more complicated objects an Auxillary View is usually needed.