What is curvature tolerance?
The concept of bending tolerance is as follows: When a sheet of metal is bent, it has three dimensions – two outside dimensions (L1 and L2) and one thickness dimension (T).
It is important to note that the sum of L1 and L2 is greater than the unfolded length (L), and the difference between the two is known as the bending tolerance (K).
Therefore, the unfolded length of a curve can be calculated as L = L1 + L2 – K.
Related reading:
- How to calculate bending tolerance, bending deduction and K factor？
Curvature Tolerance Formula
Bend Tolerance Formula for Steel
How was the formula for bend tolerance created? And how do you calculate the fold allowance?
The bending tolerance depends on the inner radius formed. The bottom opening of the V-die determines the inner radius (IR) of a formed part. The inner radius for mild steel is 5/32 x smallest die opening V (W) when the punch radius is less than 5/32 x W.
If IR< Material Thickness
Bending Tolerance Chart
The bend tolerance table is a convenient resource that lists the thickness, bend radius, bend angle, bend tolerance, or bend allowance values of common materials in a tabular format.
This information is stored in a designated location, making it easy to access and select when needed.
Further reading:
- Curvature Deduction Calculator
The tables below provide bending tolerances for iron, aluminum and copper respectively, for reference. They allow you to easily determine the required bending tolerances for different material thicknesses.
(1) Bending tolerance table for SPCC cold rolled steel sheet (SECC electrogalvanized sheet)
| television | Angle | 0.6 | 0.8 | 1 | 1.2 | 1.5 | two | 2.5 | 3 | 3.5 | 4 | 4.5 | 5 | Shortest size |
| V4 | 90 | 0.9 | 1.4 | 2.8 | ||||||||||
| V4 | 120 | 0.7 | ||||||||||||
| V4 | 150 | 0.2 | ||||||||||||
| V6 | 90 | 1.5 | 1.7 | 2.15 | 4.5 | |||||||||
| V6 | 120 | 0.7 | 0.86 | 1 | ||||||||||
| V6 | 150 | 0.2 | 0.3 | 0.4 | ||||||||||
| V7 | 90 | 1.6 | 1.8 | 2.1 | 2.4 | 5 | ||||||||
| V7 | 120 | 0.8 | 0.9 | 1 | ||||||||||
| V7 | 150 | 0.3 | 0.3 | 0.3 | ||||||||||
| V8 | 90 | 1.6 | 1.9 | 2.2 | 2.5 | 5.5 | ||||||||
| V8 | 30 | 0.3 | 0.34 | 0.4 | 0.5 | |||||||||
| V8 | 45 | 0.6 | 0.7 | 0.8 | 1 | |||||||||
| V8 | 60 | 1 | 1.1 | 1.3 | 1.5 | |||||||||
| V8 | 120 | 0.8 | 0.9 | 1.1 | 1.3 | |||||||||
| V8 | 150 | 0.3 | 0.3 | 0.2 | 0.5 | |||||||||
| V10 | 90 | 2.7 | 3.2 | 7 | ||||||||||
| V10 | 120 | 1.3 | 1.6 | |||||||||||
| V10 | 150 | 0.5 | 0.5 | |||||||||||
| V12 | 90 | 2.8 | 3.65 | 4.5 | 8.5 | |||||||||
| V12 | 30 | 0.5 | 0.6 | 0.7 | ||||||||||
| V12 | 45 | 1 | 1.3 | 1.5 | ||||||||||
| V12 | 60 | 1.7 | two | 2.4 | ||||||||||
| V12 | 120 | 1.4 | 1.7 | two | ||||||||||
| V12 | 150 | 0.5 | 0.6 | 0.7 | ||||||||||
| V14 | 90 | 4.3 | 10 | |||||||||||
| V14 | 120 | 2.1 | ||||||||||||
| V14 | 150 | 0.7 | ||||||||||||
| V16 | 90 | 4.5 | 5 | 11 | ||||||||||
| V16 | 120 | 2.2 | ||||||||||||
| V16 | 150 | 0.8 | ||||||||||||
| V18 | 90 | 4.6 | 13 | |||||||||||
| V18 | 120 | 2.3 | ||||||||||||
| V18 | 150 | 0.8 | ||||||||||||
| V20 | 90 | 4.8 | 5.1 | 6.6 | 14 | |||||||||
| V20 | 120 | 2.3 | 3.3 | |||||||||||
| V20 | 150 | 0.8 | 1.1 | |||||||||||
| V25 | 90 | 5.7 | 6.4 | 7 | 17.5 | |||||||||
| V25 | 120 | 2.8 | 3.1 | 3.4 | ||||||||||
| V25 | 150 | 1 | 1 | 1.2 | ||||||||||
| V32 | 90 | 7.5 | 8.2 | 22 | ||||||||||
| V32 | 120 | 4 | ||||||||||||
| V32 | 150 | 1.4 | ||||||||||||
| V40 | 90 | 8.7 | 9.4 | 28 | ||||||||||
| V40 | 120 | 4.3 | 4.6 | |||||||||||
| V40 | 150 | 1.5 | 1.6 |
(2) Bending tolerance table for aluminum sheet
| television | Angle | 0.6 | 0.8 | 1 | 1.2 | 1.5 | two | 2.5 | 3 | 3.5 | 4 | 4.5 | 5 | Shortest size |
| V4 | 1.4 | 2.8 | ||||||||||||
| V6 | 1.6 | 4.5 | ||||||||||||
| V7 | 1.6 | 1.8 | 5 | |||||||||||
| V8 | 1.8 | 2.4 | 3.1 | 5.5 | ||||||||||
| V10 | 2.4 | 3.2 | 7 | |||||||||||
| V12 | 2.4 | 3.2 | 8.5 | |||||||||||
| V14 | 3.2 | 10 | ||||||||||||
| V16 | 3.2 | 4 | 4.8 | 11 | ||||||||||
| V18 | 4.8 | 13 | ||||||||||||
| V20 | 4.8 | 14 | ||||||||||||
| V25 | 4.8 | 5.4 | 6 | 17.5 | ||||||||||
| V32 | 6.3 | 6.9 | 22 |
(3) Bending tolerance table for copper sheet
| Angle | 0.6 | 0.8 | 1 | 1.2 | 1.5 | two | 2.5 | 3 | 3.5 | 4 | 4.5 | 5 | Shortest size |
| 90 | 3.6 | 5.2 | 6.8 | 8.4 | 28 | ||||||||
| 120 | |||||||||||||
| 150 |
- Download bend tolerance chart PDF file
(4) Amada bending tolerance chart
| MATERIAL | SPCC | SUS | Al （LY12） |
SECC | ||||
|---|---|---|---|---|---|---|---|---|
| T | ΔT | ΔK | ΔT | ΔK | ΔT | ΔK | ΔT | ΔK |
| T=0.6 | 1.25 | 1.26 | ||||||
| T=0.8 | 0.18 | 1.42 | 0.15 | 1.45 | 0.09 | 1.51 | ||
| T=1.0 | 0.25 | 1.75 | 0.20 | 1.80 | 0:30 | 1.70 | 0.38 | 1.62 |
| T=1.2 | 0.45 | 1.95 | 0.25 | 2.15 | 0.50 | 1.90 | 0.43 | 1.97 |
| T=1.4 | 0.64 | 2.16 | ||||||
| T=1.5 | 0.64 | 2.36 | 0.50 | 2.50 | 0.70 | 2:30 p.m. | ||
| T=1.6 | 0.69 | 2.51 | ||||||
| T=1.8 | 0.65 | 3:00 | ||||||
| T=1.9 | 0.60 | 3.20 | ||||||
| T=2.0 | 0.65 | 3.35 | 0.50 | 3.50 | 0.97 | 3.03 | 0.81 | 3.19 |
| T=2.5 | 0.80 | 4:20 am | 0.85 | 4.15 | 1.38 | 3.62 | ||
| T=3.0 | 1.00 | 5:00 | 5:20 am | 1.40 | 4.60 | |||
| T=3.2 | 1.29 | 5.11 | ||||||
| T=4.0 | 1.20 | 6.80 | 1.00 | 7:00 | ||||
| T=5.0 | 2.20 | 7.80 | 2.20 | 7.80 | ||||
| T=6.0 | 2.20 | 9.80 | ||||||
Observation:
- The V12 coefficient for 2mm C-profile is 3.65 and for other 2mm boards is 3.5). The edge bending allowance for 2mm board is 1.4;
- The bend tolerance for 6mm copper plate is 10.3;
- The bend tolerance for 8mm copper plate is 12.5;
- The bend tolerance for 10mm copper plate is 15;
- The bend tolerance for 12mm copper plate is 17;
- The curvature tolerance for 3.0 stainless steel with V25 die is 6;
- The curvature tolerance for 3.0 stainless steel with V20 die is 5.5;
- (All copper bars exceeding 6mm use V40 lower die bending tolerance)
