Bend Allowance Sheet Metal K Factor Chart

There is a direct relationship between bend allowance and the k factor.

Bend allowance sheet metal k factor chart.

It allows you to anticipate the bend deduction for a large variety of angles without having to rely on a chart. The inside radii are based off of a standard air bend force chart. You can easily modify the material thickness inside radius and k factor for each thickness at the top of each column. The k factor is fundamental to designing precise sheet metal products.

Bend allowance ba π 180 r k t a. After bending the sheet insert the inner radius and flanges a and b. The below microsoft excel chart is for even numbered gauges 8 through 24 and has a default k factor of 33 for each. Should you wish to calculate the k factor rather than use a chart you will need some test pieces four or five pieces should do nicely for this purpose.

The k factor in sheet metal working is the ratio of the neutral axis to the material thickness. The k factor is the ratio between the distance from the neutral layer to the bent inner surface and the thickness of the sheet metal. To calculate the bend allowance the k factor and the derived coefficient called the y factor insert the thickness and initial length of the sheet into the cells on the left. The line where the transition from compression to stretching occurs is called the neutral axis.

A bending angle. L unfold length a outside size b outside size k k factor none 90 bend unfold according to the neutral layer the distance from neutral to sheet inner side is t 3 inner r can refer to the above chart. K value of k factor. R inside bend radius.

Bend forming 0 l a b 0 43t t thickness deduction 0 43t. Bending angle is 90. Calculate unfold size with bend allowance chart. All other values are known to the user.

The k factor is defined as a constant that is greater than 0 and less than 1. T sheet thickness. Sheet metal bend allowance chart pdf. Consider a sheet with a 20 mm thickness and a length of 300 mm as shown in figure 1.

The k factor is usually somewhere between 0 3 and 0 5. We are going to review three bending scenarios with three different bending angles. 60 90 and 120 and we will calculate k factor bend allowance and bend deduction for them. Because of the specific properties of any given metal there is no easy way to calculate that value perfectly hence the chart in figure 2.

In above bend allowance formula except sheet metal k factor and bend allowance values. While modern bend deduction charts now are reasonably accurate historically bend calculation charts both for bend allowances and bend deductions were notorious. Mathematically bend allowance during sheet metal bending can be calculated as.