K-Factor Calculator
Calculate neutral axis position and bend allowance for sheet metal bending
K-Factor Calculation
The thickness of the sheet metal being bent
The radius of the bend on the inside surface of the material
The angle through which the material is bent (0° = no bend, 90° = right angle)
The length of the neutral axis through the bend
K-Factor Results
⚠️ Validation Warnings
- • K-factor outside typical range (0.25-0.75). Verify input values.
⚠️ Manufacturing Safety Warning
• K-factor calculations are estimates - always perform test bends for critical applications
• Material properties, grain direction, and tooling affect actual K-factor values
• Verify calculations with qualified manufacturing engineers
• Consider material springback and forming temperature effects
• Improper bending parameters can cause material failure or cracking
• Use appropriate safety equipment when operating bending machinery
Example: Aluminum Sheet K-Factor Calculation
Given Parameters
Material: Aluminum 6061-T6 sheet
Thickness (T): 1.0 mm
Inner Radius (Ri): 1.0 mm
Bend Angle (θ): 90°
Bend Allowance (BA): 2.1 mm
K-Factor Calculation
• Step 1: (180 × BA) / (π × θ × T) = (180 × 2.1) / (π × 90 × 1) = 1.337
• Step 2: Ri / T = 1.0 / 1.0 = 1.000
• K-Factor = Step 1 - Step 2 = 1.337 - 1.000 = 0.337
• Neutral Axis Location = K × T = 0.337 × 1.0 = 0.337 mm
Result: K-factor = 0.337 (typical for aluminum)
Typical K-Factor Ranges
6061, 5052
low carbon
304, 316
Factors Affecting K-Factor
Material Properties
Yield strength, ductility, work hardening
Bend Geometry
Radius-to-thickness ratio, bend angle
Tooling
Die opening, punch radius, surface finish
Process Variables
Forming speed, temperature, lubrication
Key Formulas
K-Factor
K = (180×BA)/(π×θ×T) - (Ri/T)
Neutral Axis
t = K × T
Bend Allowance
BA = (K+Ri/T)×π×θ×T/180
Understanding K-Factor in Sheet Metal Bending
What is K-Factor?
The K-factor represents the location of the neutral axis within the material thickness during bending. It's expressed as a ratio of the distance from the inner surface to the neutral axis divided by the material thickness. This parameter is crucial for accurate bend allowance calculations.
K-Factor Formula
K = (180 × BA) / (π × θ × T) - (Ri / T)
- •BA: Bend allowance (length of neutral axis)
- •θ: Bend angle in degrees
- •T: Material thickness
- •Ri: Inner bend radius
Neutral Axis Concept
During bending, the material above the neutral axis experiences compression while material below experiences tension. The neutral axis length remains constant, making it the reference for calculating developed lengths and flat pattern dimensions.
Practical Applications
Sheet Metal Fabrication
Calculate flat pattern dimensions for accurate part development.
Press Brake Programming
Determine precise bend allowances for CNC programming.
Quality Control
Verify bend accuracy and material consistency in production.