Figure 2-56.Development of a truncated cylinder.
Figure 2-57.Making a grooved seam joint.
Figure 2-58.Hand groover.
Figure 2-59.Locking a grooved seam with a hand groover.
allowance for a wire edge is 2 1/2 times the diameter
of the wire used As an example, you are using wire
that has a diameter of 1/8 inch. Multiply 1/8 by 2 1/2
and your answer will be 5/16 inch, which you will
allow when laying out sheet metal for making the wire
The GROOVED SEAM JOINT (fig. 2-57) is one
of the most widely used methods for joining light- and
medium-gauge sheet metal. It consists of two folded
edges that are locked together with a HAND
GROOVER (fig. 2-58).
When making a grooved seam on a cylinder, you
fit the piece over a stake and lock it with the hand
groover (fig. 2-59). The hand groover should be
approximately 1/16 inch wider than the seam. Lock
the seam by making prick punch indentions about
1/2 inch in from each end of the seam.
The CAP STRIP SEAM (fig. 2-60, view A) is
often used to assemble air-conditioning and heating
ducts. A variation of the joint, the LOCKED CORNER
SEAM (fig. 2-60, view B), is widely accepted for the
assembly of rectangular shapes.
Figure 2-60.(A) Cap strip seam, (B) Locked corner seam