# 4130 Sheet Metal Neutral Axis Calculations

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#### FokkerDVII

##### Well-Known Member
Does anyone have a formula for locating the Neutral Axis for 4130 sheet metal when making 90 degree bends? Something in a MS Excel file would be great.

Thanks Chris

#### Jay Kempf

##### Curmudgeon in Training (CIT)
Lifetime Supporter
For flat layout calculations? Each shop has their own sort of standards. It can vary with cold rolled vs. hot rolled, rolling direction, bend radius, the design, and the actually tooling and procedures used. Generally anywhere from 35 to 50% of the material thickness from the inside of the bend is used.

#### proppastie

##### Well-Known Member
Log Member
Basic Diemaking Eugene Ostergaard R<2T C=.33T, R=2T-4T C=.4T, R=>4T C=.5T R=Inside Bend Radius, T=Thickness of material, C=Location of neutral axis. I/We always used .33T at R less than 2T and .5T at R=2T or greater. I used to calculate the bend allowance but now I just draw it in cad and measure the length of the neutral axis.

#### FokkerDVII

##### Well-Known Member
Basic Diemaking Eugene Ostergaard R<2T C=.33T, R=2T-4T C=.4T, R=>4T C=.5T R=Inside Bend Radius, T=Thickness of material, C=Location of neutral axis. I/We always used .33T at R less than 2T and .5T at R=2T or greater. I used to calculate the bend allowance but now I just draw it in cad and measure the length of the neutral axis.
Very easy to measure in CAD if you have the neutral axis location. An internet search gave me much conflicting info. Yours is the practical guideline I was looking for. Thanks.

#### proppastie

##### Well-Known Member
Log Member
Very easy to measure in CAD if you have the neutral axis location. An internet search gave me much conflicting info. Yours is the practical guideline I was looking for. Thanks.
If you draw in the tangents and center of the bend on the flat pattern, you will know where to set/offset your clamp on a pan break, or where to locate the V-die on a vertical bending press. Again a Cad drawing of the bend and tool will help in understanding.