Red Book

• Short run stamping is ideal for quantities ranging from prototypes up to 100,000 pieces. It offers a middle ground between the low tooling cost of laser cutting and the high speed of progressive dies.

  • Vs. Laser Cutting: Short run tooling is more cost-effective for complex forming that lasers cannot do, and provides tighter tolerances on holes than lasers (which can have edge taper).

  • Vs. Progressive Dies: Short run tooling costs significantly less (often 85-90% less) than progressive dies. It allows for easier design changes and is best for proving designs before committing to expensive hard tooling.

  • Vs. Turret Press: Short run stamping eliminates the “scalloped” edge finish common with turret presses and holds tighter tolerances.

Standard “low cost” design tolerances for short run stampings are typically ±.010″ on hole centers and ±.005″ on hole diameters.

• Cost Implication: Holding tighter tolerances (e.g., ±.002″ on centers) is possible but increases tooling and part costs significantly, potentially requiring shaving or secondary operations.

• Flatness: For parts under 1 inch long, a flatness tolerance of .005″ T.I.R. (Total Indicator Reading) is standard.

The minimum bend radius depends on the material alloy and temper.

• Aluminum (5052-H32): Requires a minimum radius of roughly 1.5 to 2 times the material thickness (1.5t – 2t) to avoid cracking. Soft aluminum (1100-0) can often be bent with a sharp (0) radius.

• General Rule: For economical production, specify the most generous radius possible. Sharp inside corners on heavy material cause noticeable distortion and “bulging” on the sides of the bend.

• Design Tip: If the burr side is on the outside of the bend, fractures are more likely; tumbling or filing may be required if the radius is too sharp.

To prevent hole distortion, the minimum distance from the edge of a hole to the bend line should be 1.5 times the material thickness plus the bend radius ($1.5T + R$).

• Solution if closer spacing is needed: If the design requires a hole closer than this limit, a secondary drilling or reaming operation may be required after forming, or a relief notch must be added to the bend line.

The approximate tonnage required to cut a blank (using a flat-faced punch) is calculated using the formula: Tons = Perimeter (in inches) × Material Thickness × Constant.

• Material Constants:

  • Aluminum (Soft): 11

  • Aluminum (T4/T6): 15

  • Steel (Cold Rolled): 27

  • Stainless Steel (Annealed): 37

• Example: A part with a 12-inch perimeter made of .050″ thick half-hard cold rolled steel would require approximately 20 tons of pressure.