When machined surfaces intersect, a protrusion is sometimes produced on one of the surfaces.
To meet close tolerance or functional requirements, these protrusions or burrs must be removed.
Drilling a cross hole through a cylindrical surface produces a burr where the drill pushed through the surface.
Burrs thrown up by drilling can be removed by a chamfer. It should be noted that a chamfer or countersink in a cylindrical or curved surface will be elliptical in shape as shown on the end view of the cross hole in the piece shown in Drawing #7. Designate where a countersink is measured since its dimensions will vary. A countersink on a curved surface is best dimensioned by designating the angle and the minor diameter which is the shortest distance across the edges of the countersink.