Sheet Metal Hem Radius

When working with a brake press hems are always created in a two step process.

Sheet metal hem radius. For bent sheet metal variation in the raw material thickness increases the recommended precision to 0 010 in. Unlike the u channels discussed in part iii the hem has only one bend instead of two. As a general recommendation 0 005 in. A 1 degree tolerance on all bend angles.

The minimum allowable inside radius for an acute bend in an aluminum alloy can be expressed in the following way. If the hem has a radius greater than zero it resembles a u in cross section. The smaller radius is formed first to allow the material to finish inside itself. Create a bend with acute angle tooling in the metal 30 is preferable but 45 will work for some circumstances.

Bends in sheet metal are manufactured using sheet metal brakes. Alternatively you can design with. Use this document to choose values that are both manufacturable and meet your needs. In sheet metal hemming means to fold the metal back on itself.

Bends specified as angles may be toleranced at plus or minus one half degree at a location adjacent to the bends. It is most economical to use a single bend radius throughout the design but if necessary you can utilize multiple radii. Minimum acute flat for aluminum mt x 2 minimum acute punch radius for aluminum minimum flat length x 2 hemming and seaming hemming and seaming are basically the same process. The desired radius is created by step bending a progressively larger radius into the sheet beginning with the desired curl radius minus the material thickness and ending with the desired curl radius.

A hem is a single 180 degree bend. When designing parts for laser cutting one should not make holes smaller than the thickness of the material. Some hems are closed basically a zero inside bend radius.