Bend Factor 101: Quick Guide for Sheet Metal Shops (With Formulas)
Bend Factor.When bending sheet metal, the bend factor is key—it’s the extra length you need to account for to get the final part size right. Skip it, and your parts won’t fit. Here’s what you actually need to know, plus practical formulas to calculate it:
1. What Is a Bend Factor?Bend Factor 101
Bend Factor. It’s the “hidden” length lost when metal bends (due to stretching/compression at the bend). For example, If you bend a 100mm metal strip into a 90° angle (two 40mm sides), the bend factor fills the gap between 80mm (40+40) and the original 100mm.
2. 3 Key Things That Change It
- Material type: Soft metals (aluminum) have smaller factors than hard ones (stainless steel).
- Material thickness: Thicker metal = bigger bend factor (more stretching).
- Bend radius: Tighter radius (sharper bend) = larger factor (more stress on the metal).
3. Practical Formulas to Calculate Bend Factor
Two common methods used in sheet metal shops:
A. K-Factor Method (Most Accurate for Precision Parts)
The K-factor represents how much the neutral axis (the layer of metal that doesn’t stretch/compress) shifts during bending.
- Formula 1: Bend Factor = K × Thickness (T)
(K ranges from 0.3 to 0.5; use 0.4 for most mild steels)
- Formula 2: Flat Pattern Length = Side A + Side B + (π × (Radius + 0.5T) × (Bend Angle/360°))
Example: Bend 2mm mild steel (K=0.4) into 90° with 3mm radius.
Flat length = 50mm + 50mm + (3.14 × (3 + 1) × (90/360)) = 100mm + 3.14mm = 103.14mm
B. Bend Deduction Method (Simpler for Basic Bends)
Bend deduction (BD) is the amount subtracted from the sum of sides to get the flat length.
- Formula: Flat Pattern Length = Side A + Side B – Bend Deduction
(Bend deduction = 2 × (Radius + T) – Bend Factor; use supplier charts for precomputed BD values)
4. Common Mistakes to Avoid
Don’t use the same factor for all parts! A 2mm aluminum sheet (K≈0.35) needs a different factor than a 3mm stainless steel sheet (K≈0.45). Wrong factors = wasted material and delayed projects.
Final Note: Mastering these formulas keeps your parts accurate and your workflow smooth. Have a specific bending scenario you need to calculate? Leave it in the comments!
Read more about sheet metal optimization tips
more photos:https://fuleimetal.com/acf-product/industrial-grade-aluminum-library-book-cart/
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(Ideal for fabricators, engineers, and Industry 4.0 professionals.)
