Press Stamping Tonnage Calculator

Estimate required press force for blanking and piercing from cut perimeter, sheet thickness, and material shear strength. Returns tonnage, cut force, and the shear value used.

Mild steel

45ksi

Stainless 304

62ksi

Aluminum 6061-T6

30ksi

Typical safety

1.2×

Units Switches input and result units

Cut perimeter P (in) Total active cut length per stroke

Material thickness T (in) Sheet gauge being blanked or pierced

Material Populates shear strength S

Safety factor 1.2 typical; increase for tool wear or tight tolerance

Required tonnage

32.40tons

Shear 45 ksi · SF 1.2

Cut force (before safety factor)

54,000lbs

Shear strength used

45.00ksi

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Tip Shear strength is roughly 70–80% of ultimate tensile strength for most metals. When shear data is unavailable, estimate S ≈ 0.75 × UTS for a first-pass tonnage check.

Worked example

Cut perimeter = 12 in, thickness = 0.1 in, Mild Steel 1018 (45 ksi), safety factor = 1.2.

1. Cut force F = P × T × S F = 12 × 0.1 × 45,000 F = 54,000 lbs 2. Base tonnage Tons = F ÷ 2000 Tons = 54,000 ÷ 2000 = 27 tons 3. Required tonnage with safety factor Required = 27 × 1.2 Required = 32.4 tons

Material shear strength reference

Material	Alloy	Shear (ksi)	Shear (MPa)	Notes
Aluminum	1100-O	10	70	Very soft, low blanking force
Aluminum	3003-H14	18	124	Moderate strength, general sheet work
Aluminum	5052-H32	24	165	Common sheet alloy
Aluminum	6061-T6	30	207	Heat-treated, stronger
Low carbon steel	1010 / 1018	45	310	Mild steel reference
HSLA steel	50 ksi grade	55	380	Higher press margin needed
Stainless steel	304	62	425	Higher load and tool wear
Copper	C110	22	150	Soft, common in electrical stampings
Brass	260	35	240	Moderate strength, clean edges

Common mistakes

Using UTS instead of shear. Shear strength is 70–80% of tensile. Using UTS overestimates tonnage by 25–40%.
Forgetting the safety factor. A theoretical number at nameplate capacity leaves no margin for wear or breakthrough shock.
Underestimating perimeter. Multi-punch progressive dies shear the sum of all active perimeters in a single stroke.
Mixing unit systems. In imperial, convert ksi to psi (× 1,000) before multiplying. In metric, MPa = N/mm² — use mm directly.

Warn Tonnage calculations do not cover stripping force, counter-pressure, or forming operations such as drawing and coining. Add stripping load (typically 5–20% of cut force) and verify with the die designer.

FAQ

What is stamping tonnage?

The press force required to shear, blank, pierce, or form sheet material. For blanking and piercing it is based on cut perimeter, thickness, and shear strength, multiplied by a safety factor.

Why include a safety factor for press tonnage?

To cover material variation, tool wear, clearance drift, and breakthrough shock that the ideal equation does not capture. A modest factor keeps the press out of overload territory.

How does material thickness affect tonnage?

Tonnage rises directly with thickness. Doubling the sheet thickness doubles the shearing force when perimeter and material stay the same.

Blanking vs piercing tonnage — any difference?

The basic equation is the same because both shear along a cut edge. Stripping force, punch count, and die geometry differ in practice.

What happens if press tonnage is underestimated?

The press can overload, punches chip, dies are damaged, edges degrade, and the machine may stall. Conservative sizing is standard.

Sources

ASM Metals Handbook Vol. 14 — Forming and Forging PMA Precision Metalforming Association — press sizing guides ASTM E8/E8M — tensile test, basis for shear estimates Ref Die Design Fundamentals (Paquin & Crowley)

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