Tweco 12mm Cutmaster - Manual (Page 29)

CUTMASTER 10MM, 12MM
Manual 0-5197AD 4-7 OPERATION
4.05 General Cutting Information
WARNING
Disconnect primary power at the source before
disassembling the power source, torch, or
torch leads.
Frequently review the Important Safety Pre-
cautions at the front of this manual. Be sure
the operator is equipped with proper gloves,
clothing, eye and ear protection. Make sure
no part of the operator’s body comes into
contact with the workpiece while the torch is
activated.\
CAUTION
Sparks from the cutting process can cause
damage to coated, painted, and other surfaces
such as glass, plastic and metal.
NOTE
Handle torch leads with care and protect them
from damage.
Torch Standoff
Improper standoff (the distance between the torch tip
and workpiece) can adversely affect tip life as well as
shield cup life. Standoff may also significantly affect
the bevel angle. Reducing standoff will generally
result in a more square cut.
Edge Starting
For edge starts, hold the torch perpendicular to the
workpiece with the front of the tip near (not touching)
the edge of the workpiece at the point where the cut
is to start. When starting at the edge of the plate, do
not pause at the edge and force the arc to "reach" for
the edge of the metal. Establish the cutting arc as
quickly as possible.
Direction of Cut
In the torches, the plasma gas stream swirls as it
leaves the torch to maintain a smooth column of
gas. This swirl effect results in one side of a cut
being more square than the other. Viewed along the
direction of travel, the right side of the cut is more
square than the left.
Right Side
Cut Angle
Left Side
Cut Angle
A-00512
Figure 4-13 - Side Characteristics of Cut
To make a square-edged cut along an inside diameter
of a circle, the torch should move counterclockwise
around the circle. To keep the square edge along
an outside diameter cut, the torch should travel in a
clockwise direction.
Dross
When dross is present on carbon steel, it is com-
monly referred to as either “high speed, slow speed,
or top dross”. Dross present on top of the plate is
normally caused by too great a torch to plate distance.
"Top dross" is normally very easy to remove and can
often be wiped off with a welding glove. "Slow speed
dross" is normally present on the bottom edge of the
plate. It can vary from a light to heavy bead, but does
not adhere tightly to the cut edge, and can be easily
scraped off. "High speed dross" usually forms a nar-
row bead along the bottom of the cut edge and is very
difficult to remove. When cutting a troublesome steel,
it is sometimes useful to reduce the cutting speed to
produce "slow speed dross". Any resultant cleanup
can be accomplished by scraping, not grinding.