As explained in bend allowance, when sheet metal is bent, the inside surface of the bend is compressed and the outer surface is stretched, but somewhere WITHIN the thickness of the metal lies its Neutral Axis, which is a line in the metal that is neither compressed nor stretched.

The location of the neutral line varies DEPENDING on:

• the material itself, 
• the radius of the bend,
• the ambient temperature, 
• direction of the material grain, 
• and the method by which it is being bent, ETC. 

The location of this neutral line is referred to as the K-factor.

Many CAD programs also work out bend allowances automatically by using K-factor calculations.

K-factor is a RATIO that represents the location of the neutral line with respect to the thickness of the sheet metal.

As explained in bend allowance, when sheet metal is bent, the inside surface of the bend is compressed and the outer surface is stretched, but somewhere within the thickness of the metal lies its Neutral Axis, which is a line in the metal that is neither compressed nor stretched.

The location of the neutral line varies depending on:

The location of this neutral line is referred to as the K-factor.

Many CAD programs also work out bend allowances automatically by using K-factor calculations.

K-factor is a ratio that represents the location of the neutral line with respect to the thickness of the sheet metal.