Punch and Die Design Calculator

Formula

• Clearance per side c = (% / 100) × thickness. Total clearance = 2c.
• Shear strength τ = 0.8 × UTS (MPa).
• Cutting force F_cut (kN) = τ × t × perimeter / 1000.
• Stripper force = 0.15 × F_cut. Total design force = F_cut × 1.25 × strokes.
• Press tonnage (metric T) = total design force / 9.81.
• Blanking: punch = size − 2c, die = size. All other ops on this pad: punch = size, die = size + 2c.

How it works

Cutting force uses shear strength approximated as 0.8 times UTS times shear perimeter times thickness. Clearance per side is a percentage of sheet thickness. Blanking sizes the die to the blank; piercing, notching, cutoff, lancing, trimming, shaving, and perforating size the punch to the feature. Press tonnage converts total design force to metric tons.

Choose the shear operation (Blanking through Perforating), then the cut shape. Enter size (diameter, rectangle, square side, or custom perimeter), thickness, UTS, and clearance % per side. Material chips fill UTS and a suggested clearance (aluminum 7.5%, mild steel 10%, stainless 12.5% per side). CALCULATE fills Results and updates the operation-specific punch/die sketch. Editing a field clears Results. RESET restores the Ø25 blanking defaults at 5% clearance.

Blanking puts size on the die; other ops put size on the punch

Blanking: die = size, punch = size − 2c. Other ops: punch = size, die = size + 2c.

Default blanking Ø25 at c = 0.1 mm → punch 24.8 mm / die 25.0 mm after CALCULATE.

Eight shear operations on this pad

Clearance percent: shop totals versus per-side on this pad

c = % × t (per side). F_cut = τ × t × L, then stripper and ×1.25 design factor to tonnage.

Default path: Ø25 · t2 · UTS 420 · 5% → 52.78 kN · 6.73 T. Total clearance = 2c.

Cutting force uses perimeter, thickness, and shear strength

What this calculator is not

Worked example

Blanking · Circular defaults: Ø25 mm, t = 2 mm, UTS 420 MPa, 5% clearance per side, 1 stroke. Reproduce on CALCULATE.

1. Leave Operation on Blanking and Cut shape on Circular. Confirm diameter 25, thickness 2, UTS 420, clearance 5, strokes 1.
2. CALCULATE. Perimeter = π × 25 ≈ 78.54 mm. τ = 0.8 × 420 = 336 MPa.
3. c = 0.05 × 2 = 0.1 mm. Punch = 25 − 0.2 = 24.8 mm. Die = 25 mm.
4. F_cut = 336 × 2 × 78.54 / 1000 ≈ 52.78 kN. Total design force ≈ 65.97 kN. Tonnage ≈ 6.73 T.
5. Optional: switch to Piercing, set diameter 20, CALCULATE. Punch 20.0 mm, die 20.2 mm. Try Cutoff, Lancing, Trimming, Shaving, or Perforating to see each Results sketch (same punch-size rule as piercing).

Result: Default blanking: punch 24.8 mm, die 25.0 mm, F_cut 52.78 kN, tonnage 6.73 T. Piercing Ø20 at 5%: punch 20.0 mm, die 20.2 mm. Other ops (3–7) use the same punch-size rule.

When to use

• First-pass press tonnage for blanking, piercing, or related shear ops
• Punch and die sizes with a stated clearance percent
• Comparing mild steel vs stainless clearance suggestions before tryout
• Estimating stripper load and multi-punch stroke count (perforating)
• Homework checks of F = τ·t·L with round or rectangular perimeters

Limitations

• Shear strength fixed at 0.8 × UTS. Real grades vary; override UTS or treat τ as approximate.
• No progressive-die station stacking, compound tools, or punch-face shear angle.
• Not fine blanking or near-zero clearance (shaving often wants tighter c — override %).
• Clearance chips are teaching estimates, not a supplier AHSS chart.
• Operation mode selects sizing rule and sketch only; force always uses the entered perimeter.
• Rectangular punch/die size uses the larger side only (force still uses the full 2(L+W) perimeter). Square and round apply clearance on that one dimension.
• Custom-perimeter punch/die size uses an equivalent diameter = perimeter / π for the clearance offset only.
• Stripper force is shown separately; total design force is F_cut × 1.25 × strokes (stripper not added again).
• Metric only (mm, MPa, kN, metric tons).
• Not a substitute for tooling supplier data or stamped press capacity checks.

FAQ

Blanking vs piercing: which size goes on the punch?

Blanking: die equals the blank size and punch is smaller by total clearance. Piercing, notching, cutoff, lancing, trimming, shaving, and perforating: punch equals the feature size and die is larger by total clearance.

What do cutoff, lancing, trimming, shaving, and perforating change?

They use the same punch = size, die = size + 2c rule as piercing, and each draws a different Results sketch. Force still comes from perimeter × thickness × shear strength. For perforating, set Punches / strokes to how many holes fire on one press stroke.

Is clearance percent per side or total?

This pad uses percent of thickness per side. Total (diametral) clearance is 2 × per side and appears on the Results card. Material chips convert common total charts (15/20/25%) into 7.5/10/12.5% per side.

Why 0.8 × UTS for shear strength?

Punching shear strength is often about 60–80% of tensile strength. This tool uses 80% so the first tonnage pick is on the conservative side of that band.

What does the 1.25 factor mean?

Total design force multiplies cutting force by 1.25 as a simple design allowance, then by the number of simultaneous punches. It is not a plant-specific safety factor.

Why is stripper force shown separately?

After the cut, the sheet can grip the punch. Stripper force is estimated as 15% of cutting force for spring or stripper-plate planning. Peak press demand still follows the total design force card.

Can I model progressive dies?

No. Enter strokes only for punches that fire on the same press stroke. Multi-station progressive force stacking needs a dedicated process sheet.

What shape should I pick for an odd outline?

Use Custom perimeter and enter the full shear length in millimetres. Punch/die size for custom shapes uses an equivalent diameter from perimeter / π for the clearance offset only.