Figure 13-30.~Bend allowance terms.
An angle that is more than
90 degrees when measured between legs or less than
90 degrees when the amount of bend is measured.
of a formed
angle-the opposite of leg. If each side of the angle is
the same length, then each is known as a leg.
* Flat. The flat portion, or flat, of a part is that
portion not included in the bend. It is equal to the
base measurement minus the setback.
l K number. A K number is one of 179 numbers
on the K chart that corresponds to one of the angles
between 0 and 180 degrees to which metal can be
bent. When metal is to be bent to any angle other than
90 degrees (K number of l.O), the corresponding
K number is selected from the chart and multiplied by
the sum of the radius and the thickness of the metal.
The product is the amount of setback for the bend.
end of the material can be most conveniently inserted
in the brake.
The bend line is then measured and
marked with a soft-lead pencil from the bend tangent
line closest to the end that is to be placed under the
This measurement should be equal to the
radius of the bend. The metal is then inserted in the
brake so that the nose of the brake will fall directly
over the bend line. See figure 13-32.
l Bend tangent line. The line at which the metal
starts to bend and the line at which the metal stops
curving. All the space between the bend tangent lines
is the bend allowance.
@ MuZd line. The line formed by extending the
outside surfaces of the leg and the flange.
imaginary point from which real base measurements
are provided on drawings.)
l Base measurement. The base measurement is
the outside dimension
of a formed part.
be given on the drawing
blueprint, or it may be obtained from the original part.
l Leg. The longer part of a formed angle.
l Bend line. The bend line (also called the brake
or sight line) is the layout line on the metal being
formed that is set even with the nose of the brake, and
it serves as a guide in bending the work.
forming a bend, the metalsmith must decide which
Figure 13.31.-Open and closed angles.
LINE UP BEND LINE WlTii
NOSE OF BENDING
TOOL BY USING COMBINATION
IF BEND iS MADE WITH FORM BLOCKS.
ONE BEND RADIUS
bend lines in a brake,