operate the countersink. However, it should not be
Cleco fasteners come in sizes ranging from 1/16 to 3/8
operated above 2,500 rpm. The countersink must be
of an inch. The size is normally stamped on the fastener,
sharp to avoid vibration and chatter.
but may also be recognized by the following color code:
1/16 inch--black
Snips and Shears
3/32 inch--cadmium
Snips and shears are used for cutting sheet metal
1/8 inch--copper
and steel of various thickness and shapes. Normally,
shears cuts the heavier or thicker materials.
5/32 inch--black
One of the handiest tools for cutting light (up to
3/16 inch--brass
0.064 inch thick) sheet metal is the hand snip (tin
1/4 inch--green
snips). The straight snips, shown in figure 4-8, have
3/8 inch--red
blades that are straight and cutting edges that are
sharpened to an 85-degree angle. Snips like this can be
The Cleco fastener is installed by compressing the
obtained in different sizes ranging from the small
spring with Cleco pliers (forceps). With the spring
6-inch to the large 14-inch snip. Tin snips will also
compressed, the pin of the Cleco is inserted in the
work on slightly heavier gauges of soft metals, such as
drilled hole. The compressed spring is then released,
aluminum alloys.
allowing spring tension on the pin of the Cleco to draw
the materials together. Clecos should be stored on a
It is hard to cut circles or small arcs with straight
U-channel plate to protect the pins of the Cleco. Storing
snips. There are snips especially designed for circular
Clecos at random among heavy tools will result in bent
cutting. An example is the aviation snips that are
pins.
available in a left-hand and right-hand cutting design.
To cut large holes in the lighter gauges of sheet
Countersink
metal, start the cut by punching or otherwise making a
hole in the center of the area to be cut out. With aviation
Machine countersinking is used to flush rivet sheets
snips, make a spiral cut from the starting hole out
0.064 of an inch and greater in thickness. A countersink
toward the scribed circle, and continue cutting until the
has a cutting face beveled to the angle of the rivet head,
scrap falls away.
and is kept centered by a pilot shaft inserted in the rivet
hole. When a conventional countersink is used, you
POWER TOOLS
should try each hole with a rivet or screw to ensure the
hole has not been countersunk too deeply. The
This part of the chapter is devoted to the common
adjustable countersink is the best tool to use because
types of air-driven power tools that you will use on a
the depth of the hole can be controlled. A stopping
routine basis. You should pay attention to the safety
device automatically acts as a depth gauge so that the
procedures, general operating procedures, and care of
hole will not be countersunk too deep. Figure 4-7 shows
these tools.
an adjustable stop countersink.
Rivet Head Shaver
The countersink should always be equipped with a
fiber collar to prevent marring of the metal surface. A
The rivet-head shaver, shown in figure 4-9, is used
drill motor or hand drill (electric or air) may be used to
to smooth countersunk rivet heads that protrude. The
rivet head shaver is also called a "micro miller." The
depth of cut is adjustable in increments of 0.0005 of an
inch on the model shown. On some models the depth of
cut is adjustable in increments of 0.0008 of an inch. You
can change cutters and adjust their depth without using
special tools. Once the depth is set, the positive action
of the serrated adjustment-locking collar prevents the
loss of the setting.
You should position the cutters directly over the
rivet head and hold the tool at an angle of 90 degrees to
Figure 4-7.--Adjustable stop countersink.
4-4
