# Stamping Press Tonnage Calculator for Blanking and Piercing

> Source: https://netray.co/tools/stamping-press-tonnage-blanking-piercing-calculator
> Publisher: Netray (netray.co), AI and integration engineering for ERP and manufacturing systems.
> Section: Free Tools

## Short answer

Cutting force from perimeter, thickness and shear strength, plus stripping and forming load, with a press size that includes a safety margin.

## Category

engineering-plm

## Industry

Metal Stamping

## Audience

- Estimator
- Die designer
- Process engineer

## Tool

**Kind:** calculator

**Inputs:**

#### Blank cut perimeter

**Key:** blank_p

**Type:** number

**Default:** 10

**Min:** 0

**Step:** 0.1

**Unit:** in

**Help:** Outside perimeter cut at the blanking station.

#### Total pierced perimeter

**Key:** pierce_p

**Type:** number

**Default:** 4

**Min:** 0

**Step:** 0.1

**Unit:** in

**Help:** Sum of all hole and slot perimeters that cut at the same stroke.

#### Notch and trim perimeter

**Key:** other_p

**Type:** number

**Default:** 0

**Min:** 0

**Step:** 0.1

**Unit:** in

**Help:** Other cut length in the same stroke, such as notching or cutoff.

#### Material thickness

**Key:** thk

**Type:** number

**Default:** 0.06

**Min:** 0.005

**Max:** 0.5

**Step:** 0.001

**Unit:** in

#### Material shear strength (approx)

**Key:** shear

**Type:** select

**Default:** 40

**Options:**

##### Low carbon steel, CR 1008/1010 (about 40 ksi)

**Value:** 40

##### Stainless 304 annealed (about 65 ksi)

**Value:** 65

##### Aluminum 5052-H32 (about 20 ksi)

**Value:** 20

##### Aluminum 6061-T6 (about 30 ksi)

**Value:** 30

##### Brass C260 half hard (about 42 ksi)

**Value:** 42

##### Copper C110 half hard (about 28 ksi)

**Value:** 28

#### Shear reduction from stepped or angled punches

**Key:** shear_red

**Type:** slider

**Default:** 0

**Min:** 0

**Max:** 40

**Step:** 5

**Unit:** %

**Help:** Staggered punch lengths or ground shear angle reduce peak force. 0 for flat punches.

#### Stripping force

**Key:** strip_pct

**Type:** slider

**Default:** 10

**Min:** 5

**Max:** 25

**Step:** 1

**Unit:** % of cut

**Help:** Typically 5 to 20 percent of cutting force; higher for tight clearance or thin stock.

#### Forming and drawing load at same stroke

**Key:** form_t

**Type:** number

**Default:** 0

**Min:** 0

**Step:** 0.5

**Unit:** tons

**Help:** Add bend, coin or draw load from another station that hits at the bottom of the same stroke.

#### Safety margin

**Key:** margin

**Type:** slider

**Default:** 20

**Min:** 0

**Max:** 50

**Step:** 5

**Unit:** %

**Outputs:**

#### Total cut perimeter

**Key:** perim

**Expr:** blank_p + pierce_p + other_p

**Format:** decimal

#### Cutting force, flat punches

**Key:** cut_full

**Expr:** perim * thk * shear / 2

**Format:** decimal

**Description:** Perimeter x thickness x shear strength, converted from kips to short tons.

#### Cutting force after shear reduction

**Key:** cut_t

**Expr:** cut_full * (1 - shear_red / 100)

**Format:** decimal

#### Stripping force

**Key:** strip_t

**Expr:** cut_full * strip_pct / 100

**Format:** decimal

#### Total working load

**Key:** total_tons

**Expr:** cut_t + strip_t + form_t

**Format:** decimal

**Primary:** true

**Description:** Peak tons at the bottom of the stroke.

#### Press capacity to specify

**Key:** required_tons

**Expr:** total_tons * (1 + margin / 100)

**Format:** decimal

**Primary:** true

**Description:** Select the next standard press size at or above this value.

#### Approx cutting energy per stroke

**Key:** energy

**Expr:** cut_t * 2000 * thk * 0.4 / 12

**Format:** decimal

**Description:** Rule-of-thumb work in ft-lb assuming the punch cuts about 40 percent of thickness before fracture.

**Chart:**

#### Required tonnage vs material thickness

**Type:** line

**X:** thk

**From:** 0.02

**To:** 0.125

**Steps:** 30

**Series:**

- total_tons
- required_tons

**Disclaimer:** Shear strengths are approximate typical values for common tempers. Use the mill certificate shear or 0.75 x ultimate tensile strength for the real lot. This is an estimate, not a press selection certification.

## Content

**Intro:** Choosing the wrong press size is expensive either way: too small risks stalling and broken punches, too large raises the hourly rate you quote. This calculator applies the standard perimeter x thickness x shear strength relation and adds stripping, forming and a margin.

**Sections:**

#### How to use it

**Body:** Enter every cut length that happens in the same stroke: the blank outside, pierced holes and notches. A progressive die has many stations, so sum only the stations that bottom out together. Choose a material, set the thickness, and leave shear reduction at zero unless the die uses stepped or angled punches. Add any forming or coining load that occurs at the bottom of the stroke. The output shows peak working load and the press capacity to specify after your safety margin. Use the chart to see how load climbs as you move from thin to heavy gauge.

#### The formula and its assumptions

**Body:** Cutting force in pounds equals cut perimeter in inches times thickness in inches times shear strength in pounds per square inch. Dividing the kip result by 2 gives short tons. Shear strength is roughly 0.75 times ultimate tensile strength for many steels and 0.5 to 0.7 for aluminum depending on temper. Stripping force is a fraction of cutting force. Shear reduction of 10 to 30 percent is a common design target for large blanking dies. Real peak load also depends on clearance and punch condition, so the margin matters.

**Bullets:**

- Short tons (2,000 lb) are used; multiply by 8.896 for kN.
- Dull tooling can raise the force by 20 to 50 percent.
- Do not rely on rated tonnage alone for off-center loads; check the bed-length rating.

#### Common mistakes

**Body:** The most common error is adding the whole die perimeter even when stations are staggered in time, or the opposite, ignoring forming load that lands with the cut. Another is using tensile strength instead of shear strength, which overstates the load by about a third. Running a press near its rated capacity every stroke shortens its life, which is why most shops keep a 20 to 30 percent margin. Finally, tonnage is not the only limit; energy per stroke and the eccentric load limit often decide the press for deep draws and wide dies.

**Cta:** If press capacity and hourly rates live in a routing table in your ERP, we can connect this check to the work center master so the estimate flags overloaded presses automatically.

**Faq:**

#### What is the blanking tonnage formula?

**Answer:** Force in pounds equals the cut perimeter times material thickness times the material shear strength in psi. Divide by 2,000 for short tons. For 14 inches of cut in 0.060 inch low carbon steel at 40,000 psi shear, that is about 16.8 tons.

#### How much safety margin should I use?

**Answer:** Twenty to thirty percent is common. Use more for thin gauge on stiff alloys, dull tooling risk, off-center loading or when one press runs many different jobs. Never size to exactly the rated capacity.

#### Why include stripping force?

**Answer:** The material grips the punch after the cut and the stripper must pull it free. That load is usually 5 to 20 percent of cutting force and occurs on the upstroke, but many shops add it to the sizing load for a conservative result.

#### Does shear reduction really cut the tonnage?

**Answer:** Yes. Stepping punches by about half the material thickness, or grinding a shear angle, spreads the cutting over a longer part of the stroke and lowers the peak. The total work is similar, so energy per stroke does not fall the same way.

## Search terms

stamping tonnage calculator, blanking force calculator, piercing tonnage formula, press tonnage required for stamping, punch press tonnage calculation, progressive die tonnage, shear strength tonnage, stripping force stamping

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