Selection of edge configuration is dependent upon part production processes and finished part contour. A number of edge shapes are available; of these the most prevalent are No. 1 (square and round), No. 3 (slit) and No. 5 (deburred).
No. 1 is an edge prepared to a specific contour- usually round or square. It entails a price premium and should be the preferred choice when:
No. 3 is an approximately square edge produced by slitting, with evidence of slitting fracture, burr, and toe-down (edge deformation).
The edge is part of the finished product and may affect appearance
The condition of the edge may affect fatigue in application
A very accurate width is required
An edge suitable for electroplating or welding is required
No. 5 is a No. 3 edge with the burr removed through filing or similar method. Slitting fracture and toe-down will still be present. Other edge configurations available are blunt, chamfered, beveled, and square with radius or broken corners. When special edges are ordered, a cross-sectional sketch or detailed print of the desired contour should accompany the specification.
The variety of possible edges makes this a prime area for confusion during specifying. One point to remember is that special edge configuration or preparation entails added cost. The application should always be considered first. For example, it would be overspecifying to request a No. 1 edge when a part will be blanked between strip edges.
On the other hand, underspecifying would be involved if a user requested a No. 3 "with minimum burr." This is a contradiction in terms as a No. 3 edge has maximum burr. What is really needed is a No. 1 or No. 5 edge.