Figure 2-25.Sheet-metal guage.
The length of the cut is determined by the position
of the BACK GAUGE when the metal is inserted from
the front of the shears. The FRONT GAUGE controls
the length of the cut when the metal sheet is inserted
from the rear. The front gauge is seldom used and is
usually removed from the shears. A BEVEL GAUGE
permits angular cuts to be made.
To make a cut, set the back gauge to the required
dimension by using the graduated scale on the top of
the extension arms or on the graduated section on the
bed top. Hold the piece firmly against the SIDE
GAUGE with both hands until the HOLD-DOWN
comes into position, and apply pressure to the FOOT
NOTE: KEEP HANDS CLEAR OF THE BLADE
AND FEET FROM BENEATH THE FOOT PEDAL.
RING AND CIRCULAR SHEARS (fig. 2-26) are
intended for cutting inside and outside circles in sheet
metal. The CLAMPING HEAD is positioned for the
desired diameter and the blank is inserted. Lower the
CUTTING DISC and make the cut.
SHEET-METAL BENDING AND
Sheet metal is given three-dimensional shape and
rigidity by bending. Sheet metal can be formed by
hand or with various special tools and machines.
several techniques are described in the following
Figure 2-26.Ring and circular shears
METAL STAKES allow the sheet-metal
craftsman to make an assortment of bends by hand
Stakes come in a variety of shapes and sizes. The work
is done on the heads or the horns of the stakes. They
are machined, polished, and, in some cases, hardened
Stakes are used for finishing many types of work;
therefore, they should NOT be used to back up work
when using a chisel. The following is an assortment of
the most common stakes that are used within the NCF
and Public Works Departments (fig. 2-27):
1. SQUARE STAKES (fig. 2-27, view A) have
square-shaped heads and are used for general work
Three types are used: the coppersmith square stake with
one end rounded, the bevel edge square stake that is
offset, and the common square stake. Some of the edges
are beveled and this allows them to be used for a greater
variety of jobs.
2. The CONDUCTOR STAKE (fig. 2-27, view B)
has cylindrical horns of different diameters and is used
when forming, seaming, and riveting pieces and parts
3. The HOLLOW MANDREL STAKE (fig. 2-27,
view C) has a slot in which a bolt slides allowing it to
be clamped firmly to a bench. Either the rounded or the
flat end can be used for forming, seaming, or riveting.
There are two sizes available with an overall length of
either 40 or 60 inches.
4. The BLOW HORN STAKE (fig. 2-27, view D)
has two horns of different tapers. The apron end is used
for shaping blunt tapers and the slender-tapered end is
used for slightly tapered jobs.
5. The BEAKHORN STAKE (fig. 2-27, view E)
is a general-purpose stake. The stake has a
round-tapered horn on one end and a square-tapered
horn on the other end. This stake is used for riveting and
shaping round or square work
6. The DOUBLE-SEAMING STAKE WITH
FOUR INTERCHANGEABLE HEADS (fig. 2-27,
view F) has two shanks and either one can be installed