Stamping is still the workhorse of sheet metal production, and for good reason: it relies on a press and a die to apply external force to sheet, strip, tube, or profile stock, driving plastic deformation or controlled separation to get the required shape and size. The whole game comes down to two things happening inside the die cavity—predictable material flow and controlled fracture. On the shop floor, four categories cover the vast majority of work: blanking, bending, deep drawing, and forming. Blanking alone breaks down into blanking, piercing, cutoff, and trimming, and each one has its own demands on die clearance and cutting edge geometry. Get the clearance wrong on a piercing die and you will be fighting burrs and slug pulling all shift.
From a tooling standpoint, clearance is where the design either holds up or falls apart. For blanking and piercing, the clearance between punch and die is typically set at 5–10% of sheet thickness per side, depending on material—soft aluminum sits at the low end, while stainless and high-strength steel push toward the upper range or beyond. Cutting edges need proper relief angles and enough shear on the punch face to reduce tonnage on thick stock. Bending dies have to account for springback, which means either overbending or adding a bottoming feature to the tool. Deep drawing is its own animal: draw radii, blank holder force, and die surface finish all influence whether the cup forms cleanly or tears at the punch nose. A rule of thumb many of us use is a draw radius of at least 4–8 times material thickness for the first draw, with subsequent draws tightened up.
None of this works without matching the die to the press and the material lot. Progressive dies need consistent strip feed and accurate piloting, or station-to-station alignment drifts and you start scrapping parts. Wear parts—punches, inserts, strippers—should be designed for quick change, because a die that sits on the bench waiting for a replacement punch is costing money. Keep your clearance records and edge maintenance logs current; that data is what tells you when a die is due for sharpening rather than running to failure. For more mold sourcing and tooling supplier information, visit MoldSo at www.moldso.com.