chemicals such as TapMagic will work better in most cases.
Most plastics cut perfectly fine dry, just be sure not to cut
at too high a speed as to melt the plastic (caused by
overheating). If you are having a problem with the plastic
melting, water makes a good coolant. However, mixing
water and metal tools usually leads to rust, so be cautious.
When you are preparing to cut your material, there are
a number of things you can do to help make accurate cuts.
If you are cutting metal, spray it down with layout fluid,
which is a bluish paint-like coating that allows scribe marks
to be very visible. It also comes off easily with the correct
chemical remover. Then you can use a machinist square and
scribe to draw the line. After scribing the line, mark a large
“X” on the excess material. Now when you go to cut the
material, place the cutting blade such that the blade width
is on the side with the X; this will keep your material from
being a blade widths’ shorter than planned. It will also
serve to remind you which part is the excess and which is
the actual piece.
Cutting sheet stock is best done with a jig saw or a
vertical band saw. Both allow you to make long straight
cuts in addition to complicated curves. Just be sure you are
using the appropriate blade type and tooth count for what
you are cutting. These tools can be used to cut most metal,
plastic, and wood.
Bar stock can be cut using a variety of tools but a
horizontal band saw is usually the easiest. You can also
use a vertical band saw, jig saw, sawzall, and chop saw.
Just be aware that an abrasive disk on a chop saw should
not be used for anything but ferrous metals (iron/steel).
Also, these disks can fragment and explode, so always
stand outside the path of the disk and wear full face
Carbon fiber, Kevlar, fiberglass, and other composites
require great care when cutting. The dust created when
cutting them is very harmful and should not be inhaled. If
you decide to work with these materials, be sure to use a
proper mask to filter the air you breathe, do it in a properly
ventilated area, and wet it to minimize the dust.
center of the X by deforming the material under impact.
There are two types of center punches. You can use a
spring-loaded, automatic center punch which you simply
have to line up and push down until it pops, or a manual
center punch which you line up and then hit the top with a
hammer. Both work equally well but the automatic center
punch can be more convenient.
2b) If you require high accuracy, a small center drill is the
best way to start — and countersink — the hole you wish to
drill. Center drills are unique in that they are very rigid with
very little flex so they do not wander.
3) If you are drilling a large number of holes that need to
be the same depth, an easy method is to put a “shaft
collar” on your drill bit. Usually, this is a round collar that
you set at the correct distance up the bit and lock into
place via a set screw. If you don’t have one of these, then
a thin strip of duct tape wrapped around the bit at the
correct height will work also. This will give you a clearly
defined stopping depth when drilling your holes.
4) Now you are ready to drill the actual hole. If you are
drilling a hole with a diameter of 1/4” or less, you can
simply use that size drill bit. For larger sizes, I recommend
you start with a 1/4” drill and then work your way up in
1/4” increments to the size hole you need. When you drill
these holes, be sure that the drill bit is perpendicular to the
material. This can be done easily with a drill press as seen
in Figure 2.
If you are using a handheld drill, then there are a few
tricks. The first is to use two levels or machinist squares to
keep the drill upright. Use one for keeping it upright front
to back, and the other for left to right. An assistant is a
big help while doing this because while you are controlling
the drill, they can be continuously checking the orientation
of it. If you have many holes to drill, then this method
can be very time-consuming, in which case you can
make a guide. A piece of metal with the right size hole
Drilling a hole can be very straightforward and
easy. However, doing it accurately and correctly is
a different matter. A hole generally needs to be
perpendicular to the surface of the material, placed
correctly, and made deep enough. The following is
a procedure I use when drilling a hole.
1) First, measure where you want your hole to be
and mark it with an X using a scribe.
2) Next, use either a center punch or a center drill to
create a pilot hole for the drill bit:
2a) A center punch will make a small dimple at the
FIGURE 2. A drill press is used to make perfectly
perpendicular holes in a frame rail.
SERVO 05.2008 37