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0° – 180° Bend Allowance Chart for Sheet Metal Bending

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Key takeaways:

1. Bend allowance is a crucial measurement used by mold designers to accurately calculate the flat sheet metal size needed before bending, ensuring that the final product conforms to precise dimensions and tolerances specified in customer drawings.

2. The article provides detailed bend allowance charts for different materials and thicknesses, which serve as essential references for professionals in the field to determine the necessary adjustments for various bend angles, ensuring the accuracy of the fabricated metal parts.

3. The article emphasizes the importance of understanding and applying the correct bend allowance and other related factors such as K-factor and Y-factor, which are essential for the precision and quality of the final bent metal products, highlighting the necessity of both theoretical knowledge and practical tools like bend allowance calculators.

1. What Is Bend Allowance?

The bend allowance is statistical data that has been accumulated by experienced mold designers over the years.

Subsequently, mold designers can use this data in the calculation formula to determine the unfold size of various sheet metals.

Hence, the bend allowance is a tool for mold designers to calculate the unfold dimensions of press bent parts.

The functions of bend allowance:

Punch mold designers know that the first step in the design process is to reverse the bend structure into a flat structure, step by step, once they have received the product drawings from the customer.

They then proceed to punch the flat structure and design the bending mold to meet the customer’s requirements.

The mold structure design must not only meet the customer’s drawing requirements, but also the drawing dimension tolerance requirements for precision.

The biggest challenge lies in ensuring the accuracy of the relevant unfold dimensions of stamping and bending.

2. How to Calculate Bend Allowance?

After learning about bend allowance, the next step is to calculate it.

You can directly use our bend allowance calculator to calculate the bending allowance.

Besides, the fabrication calculator can also help you calculate K-factorY-factorbend allowancebend deduction, etc.

In one of our blog post we make a very detailed analysis on this, so go ahead and check out the method to calculate the bend allowance.

3. Bend Allowance Chart

(1) Bend allowance chart for 88° & 90° bending

MaterialThicknessDeductionInside
R
AngleDiePunch
RV
Width
RAngle
Steel Plate0.81.51.390°0.580.288°
0.91.71.390°0.560.288°
11.81.390°0.580.288°
1.21.91190°0.460.288°
1.22.11.390°0.580.288°
1.52.51.390°0.580.288°
Cold Rolled
Plate
1.62.651.390°0.580.688°
1.83.4290°0.8120.688°
23.5290°0.8120.688°
2.33.75290°0.8120.688°
2.54.22.690°0.8160.688°
35.052.690°0.8160.688°
46.9490°0.8250.688°
Hot Rolled
Plate
2.33.772.690°0.8160.688°
3.25.22.690°0.8160.688°
4.27.4490°0.8250.688°
4.88.1490°0.8250.688°
Aluminum Plate0.81.51.390°0.560.288°
11.61.390°0.580.288°
1.22.11.390°0.580.288°
1.52.451.390°0.580.288°
1.62.71.390°0.580.688°
1.62.41.390°0.6100.688°
23.25290°0.8120.688°
2.33.62.690°0.8160.688°
2.54.22.690°0.5160.688°
34.72.690°0.8160.688°
3.252.690°0.8160.688°
3.55.9490°0.8251.588°
46.8490°0.8251.588°
58.1490°0.8253.288°
Copper Plate0.81.61.390°0.560.288°
11.91.390°0.580.288°
1.22.151.390°0.580.288°
1.52.551.390°0.580.288°
23.5290°0.8120.688°
2.54.22.690°0.8160.688°
352.690°0.8160.688°
3.25.12.690°0.8160.688°
3.56490°0.8251.588°
47490°0.8251.588°

(2) Sheet metal bending allowance table (iron, aluminum, copper)

TCold-rolled steel sheet SPCC (electro-galvanized sheet SECC)
VAngle0.60.811.21.522.533.544.55Min dimensionNote
V4900.91.42.8
1200.7
1500.2
V6901.51.72.154.5
1200.70.861
1500.20.30.4
V7901.61.82.12.45
1200.80.91
1500.30.30.3
V8901.61.92.22.55.5
300.30.340.40.5
450.60.70.81
6011.11.31.5
1200.80.91.11.3
1500.30.30.20.5
V10902.73.27
1201.31.6
1500.50.5
V12902.83.654.58.5
300.50.60.7
451,01.31.5
601.722.4
1201.41.72
1500.50.60.7
V14904.310
1202.1
1500.7
V16904.5511
1202.2
1500.8
V18904.613
1202.3
1500.8
V20904.85.16.614
1202.33.3
1500.81.1
V25905.76.4717.5
1202.83.13.4
150111.2
V32907.58.222
1204
1501.4
V40908.79.428
1204.34.6
1501.51.6
TAluminum sheet L2Y2 material
VAngle0.60.811.21.522.533.544.55Min dimensionNote
V41.42.8
V61.64.5
V71.61.85
V81.82.43.15.5
V102.43.27
V122.43.28.5
V143.210
V163.244.811
V184.813
V204.814
V254.85.4617.5
V326.36.922
TCopper sheet
VAngle0.60.811.21.522.533.544.55Min dimensionNote
903.65.26.88.428
120
150

Note: (For C-shaped profiles with a thickness of 2.0, the V12 coefficient is 3.65, while other 2.0 sheet materials have a coefficient of 3.5.) The bending allowance coefficient for 2.0 sheet with hemming is 1.4.

  • 6.0mm copper sheet bending allowance: 10.3
  • 8.0mm copper sheet bending allowance: 12.5
  • 10.0mm copper sheet bending allowance: 15
  • 12.0mm copper sheet bending allowance: 17
  • 3.0mm stainless steel with V25 allowance: 6
  • 3.0mm stainless steel with V20 allowance: 5.5
  • For copper plates thicker than 6.0, the allowance for the lower die is V40

(3) Amada bend allowance chart

MATERLALSPCCSUSLY12SECC
TΔTΔKΔTΔKΔTΔKΔTΔK
T=0.61.251.26
T=0.80.181.420.151.450.091.51
T=1.00.251.750.21.80.31.70.381.62
T=1.20.451.950.252.150.51.90.431.97
T=1.40.642.16
T=1.50.642.360.52.50.72.3
T=1.60.692.51
T=1.80.653
T=1.90.63.2
T=2.00.653.350.53.50.973.030.813.19
T=2.50.84.20.854.151.383.62
T=3.0155.21.44.6
T=3.21.295.11
T=4.01.26.817
T=5.02.27.82.27.8
T=6.02.29.8

(4) Aluminum sheet bending allowance table

Aluminum sheet thicknessBending angleBend allowance
AL-0.8901.5 
AL-1.0901.5 
45, 1350.5 
AL-1.2902.0 
45, 1350.5 
AL-1.5902.5 
45, 1350.5 
60, 1201.5 
AL-2.0903.0 
45, 1351.0 
60, 1202.5 
90-degree groove1.5 
AL-2.5904.0 
45, 1351.5 
60, 1203.0 
90-degree groove2.0 
AL-3.0905.0 
45, 1353.0 
60, 1204.5 
90-degree groove2.5 

(5) 0°-180° sheet metal bending allowance table

Example of Calculating and Labeling the Bending Allowance for the Unfolded Dimensions of a Bent Part.
a) φ>90° b)≤90°

1) The bending allowance table is applicable for sheet metal bending processes where no pressure plate is used, and the width of the plate is greater than three times the thickness.

2) When bending on a press brake machine, calculations can be made according to this table.

3) As per the dimensions marked in the diagram, the calculation formula for the unfolded dimensions of the bent workpiece is as follows:

L = a + b + x

In this equation,

  • L – the unfolded dimensions of the bent workpiece;
  • a and b – the lengths of the straight sides of the bent workpiece as marked in the diagram;
  • x – the bending coefficient of the bent workpiece.

4) Due to the numerous factors affecting sheet metal bending, this bending allowance table for sheet metal bending should be used as a reference only.

4. Calculate Unfold Size With Bend Allowance Chart

Bend Allowance Chart

Bend forming 0°L=A+B-0.43T, T=Thickness, Deduction=0.43T

Formula: L(unfold length)=A(Outside size)+B(Outside size)-K(K-factor)

None-90° bend unfold according to the neutral layer, the distance from neutral to sheet inner side is T/3, inner R can refer to the above chart.

V-die width is 6-8 times the plate thickness

None-90°bend = 180°- Angle/90°*Deduction

The deduction is 1.8 times the steel plate thickness and 1.6 times the aluminum plate.

For plate under 2mm, K-factor is 0.432, R=plate thickness, unfold size can accurate to 0.05.

Generally, when design the sheet metal parts, the min inner R=thickness/2, if less than that, the grooving (V-cutting) will be required to solve the problem.

Further reading:

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