Internal Sharp Corners and Intersecting Surfaces


A precisely “sharp” corner can never be produced at intersecting surfaces in metalworking. But where a sharp corner is required, it can be produced within specified limits, which usually are close enough to meet the functional requirements of the part. A dimension should be placed on each intersection of surfaces where precision is required.

Typical intersecting inside surfaces are shown in Figure 1; and Figure 2 shows how they can be dimensioned.

If a corner break is not functional, the kind of break should be left to the supplier. He may be able to use a .015″ x 45° break or a .015″ radius maximum, depending on where the corner is located.

A radius is usually designated for an inside corner, such as B shown on Figure 1. Corner breaks or chamfers will usually be designated for outside corners like A and C on Figure 1. A radius specified for an outside corner will require blending into each intersecting surface, which is sometimes difficult to do.

A note “Break All Corners” is vague and confusing to those used to working to .001″ dimensions. If an intersection is a critical area on a part, it should be given a maximum and minimum dimension. If it isn’t a critical intersection, the tolerances should be as open as possible consistent with part use.