Brake Press Set-up Aids: Notes of Interest

Press Brake Deflection

A common problem for anyone using more than half the rated capacity of a press brake is deflection. The middle of the bed and ram of the press spread apart under load. This spreading can cause the angle in the middle of the part to be one to three degrees open compared to the ends.

In some presses the bed and ram do not deflect in an even curve. The deflection can be mapped out for a press that is doing a particular job by taking accurate measurements along the length of test pieces. This deflection curve can then be reproduced by the machine.

There are a number of ways to solve the deflection problem:

  • Shim the bottom (crowning) die manually by using a roll of adding machine paper. Start in the middle with a short piece, gradually increasing the length of the layers. The number of layers may be increased or decreased as required. Three layers of paper equals approximately 0.012-0.015 inches.
  • If you are working within a small range of material thickness, the crown required may be reasonably consistent. Map out the deflection and machine it into the riser block.
  • If you have dedicated tooling for a specific job, map out the deflection and have the tooling crowned.
  • Purchase a “Mecon Deflection-Compensating Die Holder.”

Mecon Deflection-Compensating Die Holder.

  • Multi point calibrating adjustment.
  • Crown read-out indicators.
  • Patent#1234039

Offset Dies

The relation between depth of offset and metal thickness affects the accuracy of the 90° bends. Good results in material up to 18 gauge can generally be obtained by bottoming, if the depth of the offset is six to eight times the metal thickness. The press brake tonnage requirements are approximately five times that needed for a single 90° air bend. When forming heavy gauge sheets, the depth of offset should be greater than eight times metal thickness.

Tonnage requirements can be reduced by air bending rather than bottoming (compromising on accuracy), and also by using larger radii on the forming points.

Radius Dies

When the radius exceeds four times material thickness, spring-back must be compensated for in the dies. The large radius used to prevent fracturing may also create problems such as material pre-bending, causing fluting and pulling away from the punch radius. Such pre-bending may require coining the radius at the bottom of the press stroke and adding to the tonnage. When forming exceptionally large radii, a bumping die will often prove more practical than a large deep die.


When bending mild steel plate 1/2″ thick and heavier or high strength materials, fracturing can be reduced by increasing die opening to 10 to 12 times material thickness. Increasing the punch radius also reduces fracturing. Tonnage Increase: When making 90° bends the pressure to form the material rises rapidly to reach 85% of maximum when the material is bent up only 20°, and a maximum when the material is bent up 40°.

Channel Dies

The corner sharpness requirements and the flatness of the bottom of the channel have a direct bearing on the tonnage applied. Increasing corner radii reduces tonnage and helps in achieving a flatter bottom. Results depend on material which is uniform in thickness, temper, and yield point.

Brake Press Set-up Aids

Standard Guage for Steel Sheets

PressBrake Features

Common Types of Brake Punch Tongues – Others on Request

Box Forming

Special clearance on ends of tools can be furnished to suit your individual requirements.
A box-forming punch and die in a 12-inch die space with a ram width of 2-1/2 inches. Graduations indicate minimum punch height required for various box depths.
Adjustable gauge arms set up with disappearing stops for multiple bends.

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Brake Press Tonnage Chart

Tons Required Per Linear Foot to Bend Mild Steel Plate Having 60,000 PSI Tensile Strength

Thickness of MATERIAL
Width of Die opening
GaugeInches1/4"5/16"3/8"7/16"0.53/8”0.750.8751 ” 1.1251.251.52"2.53"3.54"5"6"7"8"10"12"
Notes: The tonnages indicated in bold italics are for die openings eight times the thickness of the metal.
With an 8:1 die ratio, the inside radius of a right angle bend is approximately equal to the thickness of the material.

For other metals as compared to 60,000 PSI tensile strength mild steel adjust as follows:

  • Soft brass: 50% of pressure listed.
  • Soft aluminium: 50% of pressure listed.
  • Stainless steel: 50% more than pressure listed.
  • Chrome molybdenum: 100% more than pressure listed.

Brake Press Bending Allowance Chart

Bend Allowances for 90° Bends in Low‑Carbon Steel and Aluminum (Al)

Bend Allowances for 90° Bends in Low-Carbon Steel and Aluminum
Bend allowance, inches, for bends with inside radius (r) of:
(t), in.
1/32 in.1/16 in.3/32 in.1/8 in.1/4 in.1/2 in.

Bend Allowances for 90° Bends in Low-Carbon Steel and Aluminum (Metric)
Bend Allowance (mm) for Bends with Inside Radius (r) of:
Metal Thickness
( t ), mm (Inches)
0.8 mm(1/32")1.6 mm(1/16")2.4 mm(3/32")3.2 mm(1/8")6.4 mm(1/4")12.7 mm(1/2")
0.8 (0.032")
1.3 (0.050")
1.6 (0.062")2.72.432.73.433.
2.0 (0.078")
2.3 (0.090")
3.2 (0.125")
4.8 (0.188")
6.4 (0.250")9.78.6108.910.49.310.89.612.113.2
8.0 (0.313")1212.412.713.114.517.2
9.5 (0.375")14.414.715.115.416.819.5
11.1 (0.437")16.717.117.417.819.121.8
12.7 (0.500")19.119.419.720.121.524.2

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w = a + b + c + d + e –
(4 x bend allowance)

w = a + b –
(single bend allowance)

w = a + b + c –
(2 x bend allowance)

w = a + b + c + d –
(3 x bend allowance)

Note: w = developed width of blank, t = metal thickness, r = inside radius of bend

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Thinking Safety

We strive to supply tooling which allows the safe production of parts. As we have no control over how our dies are used, it must be understood that the user is responsible for ensuring that the proper methods, with due regard to safety in operation, are followed. Safety and industrial standards must be considered to ensure that the point-of-operation safety measures are effective.

Our dies are never intended to be used in equipment without a means provided to prevent hands or other body parts from entering or remaining in the die space at any time.

To prevent injury:

  • Require that dies be set only by a qualified, safety-conscious die-setter.
  • Insist that the die-setter be fully familiar with the press or machine’s manual.
  • Provide all point-of-operation guards or devices necessary to avoid exposing any part of the operator’s body to the closing of the machine or press.
  • Provide hand tools to insert, hold, and remove material, and to keep hands at a safe distance from the point of operation.
  • Insist on safety practices and procedures and enforce them daily.
  • Follow the instructions provided in the manual for the machine in which dies are being installed and operated.
  • Ascertain that operators are trained in safety procedures, and arrange for periodic inspections to ensure that those procedures are being followed.
  • Make available such safety-standard approved devices as pull-backs, fences, and infrared light curtain and controls for all press equipment. Two-button operation may also be necessary in some instances.

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