How do you bend sheet metal?

To bend sheet metal, measure out and indicate center and setback lines, then use a vise-and-block set-up to secure the sheet metal. With a mallet, hammer the desired angle into shape.

1. Mark the bend line

   Using a dry-erase marker and straight-edge, draw a straight line where you want the sheet metal to bend.

2. Calculate the bend allowance

   The setback calculation tells you the where to expect the bend to begin and end with respect to the center line. Indicate these lines from the center line with the dry-erase marker. This calculation also predicts the leg lengths after bending: setback = tangent(degree/2) * RT, where "T" is the thickness of the sheet metal, "R" is the radius of the inner bend and degree is the measure of the complementary angle.

3. Clamp the sheet metal in a vise

   Use two metal or wood blocks to sandwich the piece of sheet metal, then clamp them in a vise. It is recommended to make the edge of the inner block rounded with the desired radius of the bend.

4. Bend the sheet metal

   Using a plastic, rubber or rawhide mallet, evenly hammer the protruding end of the sheet metal until it bends into the desired angle. If a large amount of sheet metal extends from the vise-and-block set-up, hold the sheet metal with one hand to prevent the material from bouncing.