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When you choose one of our ironworkers,
you’ll get the responsiveness, versatility and
dependability you need for non-stop metal fabricating.
With the multiple workstations on our machines,
you can go from one operation to another without
time-consuming tooling changes. Get the most out of
a day’s work in your shop with these affordable,
metal-eating, American-made machines.
Using the Right
Tips focus the plasma stream to the
workpiece. Some plasma cutters use
separate tips for the high and low end
of their amperage ranges. For instance,
an 80-amp plasma cutter may use 80-
amp and 40-amp tips, plus extended
versions of those for increased reach,
as well as gouging tips.
The higher-amp tip is used when
the plasma cutter is set to its upper
amperage ranges for cutting thick
material. As noted previously, to
maintain a thin kerf when cutting
sheet metal, set the machine to a
lower-range amperage and use a low-amp tip. Because a low-amp tip has a
smaller orifice, it maintains a narrow
plasma stream at lower settings for use
on thin-gauge material. Using a 40-
amp tip at an 80-amp setting will distort the tip orifice and require replacement. Conversely, using an 80-amp
tip on the lower settings will not allow
you to focus the plasma stream as well
and creates a wide kerf.
Use extended tips to cut patterns
or to reach into corners or tight areas.
Use gouging tips to spread the plasma stream and the arc so you can
remove a large amount of material all
at once in a single pass.
If you are using clean, dry air and
making long cuts, you can expect your
consumables to last for approximately
two hours of continuous cutting time.
Continuously restarting the pilot arc
by triggering the torch shortens consumable life. Touching the tip to the
material without a drag shield in place
causes double arcing, because the electrical current tries to find the shortest
path to the workpiece. This decreases
consumable life too.
If you’re not using a drag shield, or are
trying to make very precise cuts, place
your noncutting hand down (see Figure
5) and use it as a guide for the other
hand. This rest hand position allows
freedom of movement in all directions
while helping you steady your hand and
maintain a constant standoff.
Keep the torch perpendicular to
the workpiece whenever possible,
except when you are beveling.
When you are piercing thin material to start a cut, you may be able to
punch through it with little or no arc
backsplash. However, on thick material, start with the torch on a 45-
degree angle so the first blast of metal
has somewhere to go. If not, the metal
will splash back and quickly wear your
As noted, at the optimal travel
speed, the arc will exit the material at
a 15- to 20-degree angle opposite the
direction of travel. Therefore, the cut
also will be at an angle opposite the
direction of travel. At the end of a cut,
angle the torch forward to cleanly cut
the last bit of metal (see Figure 6).
Guides. To mark the material to be
cut, use either a black marker or white
chalk. Contrast makes the marks easier to see.
For more precise cutting, you may
clamp a straight edge to the workpiece
to guide the torch (see Figure 7). If
you’ll be making multiple cuts of the
same shape, create a template.
Make sure the guide isn’t flammable. Aluminum is preferable because
of its smooth surface, but because of its
electrical conductivity, the aluminum
should touch the torch cup or drag
shield and not contact the tip.
Circle guides also are available to
help ensure precise cutting (see Figure
8). A center punch is used in preparation for using a circle-cutting guide.
An easy way to make a bevel cut is to
use a piece of angle iron as your guide
(see Figure 9).
While it may be easy enough to
unpack your plasma cutter and begin
cutting, take the time to familiarize
yourself with its proper operation. It
bears repeating that you should read
the owner’s manual first. ■
Don Keddell is the plasma training
manager for Miller Electric Manufacturing Co., 1635 W. Spencer St., Appleton, WI 54912-1079, 920-734-9821,
Want more information?
Visit www.thefabricator.com; enter the article number (digits only) in the
home page search box:
• “Starting from scratch” 1445
• “Older plasma and laser cutters having performance fits? Retrofit!” 1477
• “What to know before selecting a manual plasma cutter: Understanding size,
power, components, cost” 509
The FABRICATOR | An FMA Publication
www.thefabricator.com | March 2007