bar folder and forced into place around the wire with
a setting hammer or pliers (fig. 2-42).
Turning a Burr. A BURR, in sheet-metal
language, is a narrow flange turned on the circular
section at the end of a cylinder (fig. 2-43). Before you
cut the section, remember that additional material
must be added to the basic dimensions of the object
for the burr. Figure 2-44 shows how to calculate the
After the rotary machine has been adjusted to turn
the proper size burr, the work is placed in position and
the upper roll lowered. Make one complete revolution
of the piece, scoring the edge lightly. Lower the upper
roll a bit more, creating more pressure, and make
another turn. Continue this operation, raising the disc
slightly after each turn until the burr is turned to the
required angle (fig. 2-45).
This procedure is also used to turn the burr on the
bottom of the cylinder for a double seam (fig. 2-46).
The two pieces are snapped together, the burr set
down, and the seam completed (fig. 2-47).
NOTE: Because turning a burr is a difficult
operation, you should turn several practice pieces to
Figure 2-42.Setting a wire edge with a setting hammer or
Figure 2-43.Burrs turned on a cylindrical section.
Figure 2-44.Calculating the material needed for a double
Figure 2-45.Turning a burred edge.
Figure 2-46.Fitting burred sections together.
develop your skill before turning the burr on the actual
piece to be used.