What size press brake do you actually need in terms of tonnage, and how can you calculate the press brake tonnage? The answer to both questions is the same.

There are three methods for determining the hydraulic bending force or the tonnage of the press brake required to bend sheet metal of a specific thickness:

**By the press brake tonnage chart****By the bending force calculation formula****By the press brake tonnage calculator**

Once you have confirmed the tonnage of the press brake, you can then consider other factors such as press brake components, tooling, controllers, etc. before making a purchase decision.

In this article, we will guide you in determining the required bending force for your sheet metal.

## Press Brake Tonnage Calculator Basics

Calculating the tonnage required for a press brake operation is an important step in ensuring that the machine can safely and effectively bend the metal sheet. Tonnage refers to the amount of force that the press brake can exert on the metal sheet.

**Importance of Tonnage Calculation**

The importance of tonnage calculation lies in the fact that using a press brake with insufficient tonnage can result in damage to the machine or the metal sheet, while using a press brake with excessive tonnage can result in over-bending or cracking of the metal sheet.

**Factors Affecting Tonnage**

Several factors can affect the tonnage required for a press brake operation. These include the thickness and type of metal being bent, the desired bend angle and radius, and the length of the bend. Specialized tonnage calculators are available to help operators determine the appropriate tonnage for a given bending job.

## Factors Consideration for Calculating Press Brake Tonnage

To calculate the tonnage required for a press brake operation, several factors must be taken into account. These include the material type and strength, material thickness, bending radius, and bending length.

**Material Type and Strength:** Different types of metal have different strengths and require different amounts of force to bend. For example, bending steel requires more force than bending aluminum.

**Material Thickness:** The thicker the metal sheet, the more force is required to bend it. Tonnage calculators take the material thickness into account when determining the required tonnage.

**Bending Radius:** The smaller the desired bend radius, the more force is required to achieve it. Tonnage calculators take the desired bend radius into account when determining the required tonnage.

**Bending Length:** The longer the bend, the more force is required to achieve it. Tonnage calculators take the bending length into account when determining the required tonnage.

By taking these factors into account, a tonnage calculator can provide an accurate estimate of the tonnage required for a given press brake operation.

## Press Brake Tonnage Charts

The following press brake tonnage chart is widely used by many press brake manufacturers in China and other countries.

Although different suppliers may use slightly different charts, the final results are usually comparable, as most of them are similar.

Therefore, you can use any of them as a reference.

Note: If there are no specific requirements for the bending radius, the V-slot width should be 8 to 10 times the plate thickness.

### How to Read Press Brake Tonnage Charts?

The tonnage indicated in the press brake tonnage chart is based on a sheet metal with a tensile strength of σb=450N/mm² and a length of L=1m.

Now that you have the bending force chart, the next step is to understand how to locate the press brake tonnage in the chart.

To do this, you first need to know the meanings of “S,” “V,” “B,” and “R” in the chart.

Please refer to the accompanying images to comprehend their meanings.

- P = Bending force
- S = Thickness of sheet
- V = Vee opening of the bottom die
- B = Min bending flange
- R = Inner radius

Assuming your metal sheet has a thickness of 4mm, the general rule is that the V-opening of the bottom die should be 8 times the sheet’s thickness.

However, when dealing with thicker plates, a larger V-opening is necessary.

The recommended V-openings listed below can serve as a reference:

S | 0.5-3mm | 3-8mm | 9-10mm | >12mm |

V | 6*S | 8*S | 10*S | 12*S |

Let’s consider a metal sheet with a thickness of 4mm.

Typically, the vee opening of the bottom die should be 8 times the thickness of the sheet. However, for thicker plates, the vee opening should be larger.

To determine the required press brake tonnage, we need to refer to the press brake tonnage chart.

First, find the row with a thickness value of “4” and then determine the corresponding vee opening value of 32 (4 * 8).

The intersection of the row and column where the “4” and “32” values meet indicates a tonnage of 330 KN.

If we need to bend a 4mm sheet that is 3 meters long, the required tonnage would be 330 * 3 = 990 KN, or approximately 101 tons. In this case, we recommend choosing a press brake with a tonnage of at least 100 tons.

However, it is better to opt for a larger tonnage, such as 120 tons, as the service life of the machine will be longer if it operates at full load for extended periods of time.

**Bending Force Calculation Formula**

In addition to using the bending chart, you can also calculate the required bending force using the bending force formula.

### #1 What Is The Bending Force Calculation Formula?

The press brake bending force calculation formula is:

**P=650 S²L/V (σb=450N/mm²)**

- P: bending force (KN)
- S: plate thickness (mm)
- L: plate width (m)
- V: bottom die slot width (mm)

**For example:**

Plate thickness S=4mm, width L=3m, σb=450N/mm²

Generally slot width V=S*8

Therefore P=650**4²**3/4*8=975 (KN) = 99.5 (Ton)

The result obtained using the bending force formula is very similar to the data in the bending force chart.

Note that method #1 to calculate the press brake tonnage is based on mild steel material.

If the material is stainless steel, aluminum, or brass, you can easily adjust the calculation results by multiplying them with the coefficients listed in the following table.

Material | Coefficients |

Mild Steel | 1 |

Stainless Steel | 1.6 |

Aluminum | 0.65 |

Brass | 0.5 |

### #2 Tonage Calculation Formula

Another press brake tonnage calculation formula is:

**P=1.42 σbS²*L/V**

- P: bending force (KN)
- S: plate thickness (mm)
- L: plate width (m)
- V: bottom die slot width (mm)
- σb: tensile strength (Mpa)

**For example:**

Plate thickness S=4mm, width L=3m, σb=450N/mm²

Generally slot width V=S*8

Therefore P=1.42*450*4²*3/4*8=958.5 (KN) = 96 (Ton)

The key to bending sheet metal with different materials is to determine the tensile strength of that specific material, then calculate the required bending force using the above formula.

The tensile strength table below can be the reference:

Material | Soft (N/mm²) | Hard (N/mm²) |
---|---|---|

Lead | 25 – 40 | – |

Tin | 40 – 50 | – |

Aluminum | 93 | 1710 |

Aluminum Alloy Type 4 | 230 | 480 |

Duralumin | 260 | 480 |

Zinc | 150 | 250 |

Copper | 220 – 280 | 300 – 400 |

Brass (70:30) | 330 | 530 |

Brass (60:40) | 380 | 490 |

Phosphor Bronze / Bronze | 400 – 500 | 500 – 750 |

Nickel Silver | 350 – 450 | 550 – 700 |

Cold Rolled Iron | 320 – 380 | – |

Steel .1% Carbon | 320 | 400 |

Steel .2% Carbon | 400 | 500 |

Steel .3% Carbon | 450 | 600 |

Steel .4% Carbon | 560 | 720 |

Steel .6% Carbon | 720 | 900 |

Steel .8% Carbon | 900 | 1100 |

Steel 1.0% Carbon | 1000 | 1300 |

Silicon Steel | 550 | 650 |

Stainless Steel | 650 – 700 | – |

Nickel | 440 – 500 | 570 – 630 |

**New Bending Force Calculation Formula**

In air bending, the opening width V of the lower die is typically chosen to be 8 to 10 times the thickness of the sheet, S.

Press brake manufacturers often list the corresponding values of the die width, V, and the inner diameter, r, of the bending workpiece on their bending force parameter table.

As a general rule, **r=(0.16~0.17)V**

However, when the inner radius is not equal to (0.16-0.17)V, the above calculation formula is no longer applicable.

In these cases, you must refer to a new calculation method to determine the required bending force or press brake tonnage.

The following is the calculator:

**Press Brake Tonnage Calculator**

Finally, I highly recommend using the press brake tonnage calculator as it is likely the best and most convenient method for calculating the necessary bending force.

**Further reading:**

There is a similar press brake tonnage chart created by a professional European press brake tooling manufacturer.

This can also serve as your reference. Here it is:

**Related reading:** How to Calculate Bending Force in Air Bending (Sheet Metal)?

## Press Brake Bending Material Considerations

When using a press brake to bend metal sheets, it is important to consider the type of material being used. Different materials have different properties that can affect the bending process.

**Steel and Its Varieties:** Steel is a common material used in sheet metal fabrication. It is strong and durable, but requires a significant amount of force to bend. There are several varieties of steel available, including mild steel, stainless steel, and high-strength low-alloy steel. Each variety has its own unique properties and bending characteristics.

**Aluminum and Its Alloys:** Aluminum is another common material used in sheet metal fabrication. It is lightweight and easy to bend, but is not as strong as steel. There are several alloys of aluminum available, each with its own unique properties and bending characteristics.

**Brass and Other Metals:** Other metals such as brass, copper, and titanium can also be used in sheet metal fabrication. Each of these metals has its own unique properties and bending characteristics.

It is important to carefully consider the type of material being used when planning a press brake operation, as this can affect the tonnage required and the final result of the bend.

## FAQs

**Q: What is a press brake tonnage calculator?**

A: A press brake tonnage calculator is a tool used to calculate the amount of force required to bend a metal sheet using a press brake. It takes into account factors such as the material type and strength, material thickness, bending radius, and bending length to provide an accurate estimate of the required tonnage.

**Q: Why is it important to calculate the tonnage required for a press brake operation?**

A: Calculating the tonnage required for a press brake operation is important to ensure that the machine can safely and effectively bend the metal sheet. Using a press brake with insufficient tonnage can result in damage to the machine or the metal sheet, while using a press brake with excessive tonnage can result in over-bending or cracking of the metal sheet.

**Q: What factors affect the tonnage required for a press brake operation?**

A: Several factors can affect the tonnage required for a press brake operation. These include the material type and strength, material thickness, bending radius, and bending length.

**Q: Can I use a press brake without calculating the required tonnage?**

A: It is not recommended to use a press brake without first calculating the required tonnage. Using a press brake with insufficient tonnage can result in damage to the machine or the metal sheet, while using a press brake with excessive tonnage can result in over-bending or cracking of the metal sheet.

**Q: Are there any alternatives to using a press brake tonnage calculator?**

A: Yes, there are other methods for calculating the required tonnage for a press brake operation. These include using charts or tables provided by the press brake manufacturer, or using formulas to manually calculate the required tonnage.

Nakulhello sir,

I need to be perform bend with inner radius of r 47 bend angle is 90 degree , material is ss 304 with 3 mm thickness , could you please suggest best suitable die. I have 260 t machine .

ShaneSure, I will send an email to you.