5
air pressure or the incorrect strokes per minute range. This
can make your machine difficult to control for fine work. The
GraverMach AT has extremely fine control for the smallest stone
setting and the finest engraving. However, you must learn to tune
the machine correctly to achieve this fine control. After you are
comfortable with your handpiece control, you can experiment
with variations in air pressure and stroke speed to suit your work
preference.
HOW TO HOLD YOUR HANDPIECE
(Fig. 6) Normally, you should
hold your handpiece like
a table knife, not like a
pencil. Some exceptions are
hammering and stippling.
Resist the urge to grip your
handpiece tightly. Train yourself
to hold the handpiece as lightly
as you can. When you grip it
tightly or push hard with your
hand, you lessen the impact
power and create more work
for yourself! So, relax and let
the machine do the work while
you concentrate on the design
you are working on. When you
are doing heavy work, try this:
partially release your grip on
the handpiece as you add more
power with the foot control. You
will be amazed at how much
more power you have! If you
slip with the graver, you are
not operating your handpiece properly, and probably pushing too
hard with your hand. Hammering is a special situation. When
hammering you usually hold the handpiece like a pencil. If you
are hammer setting, be sure to press the hammer tip down firmly
on the work BEFORE using the foot control to start hammering.
Also, do NOT operate the hammer by holding the tip slightly
above the work as with many flexible-shaft hammers. Do NOT
allow the hammer tip to bounce against the work. Use just
enough downward pressure to keep the hammer from jumping
off the work. GRS handpieces have tremendous power. Use just
enough power to do the work ... take it easy at first!
HOW TO USE THE FOOT THROTTLE
Set the hand/foot control selector knob to the foot control position
(Fig. 8-E). The GraverMach AT foot throttle is operated like an
automobile accelerator and NOT like a flexible-shaft foot control.
Begin by placing your foot on the top plate with your heel resting
against the inside of the bottom bend on the top plate (Fig. 7).
You should put the tool in position BEFORE depressing the foot
throttle. Never depress the foot throttle and then try to bring a
stroking handpiece to the work! If you need more power when
cutting deeper, push more on the foot throttle to increase the
handpiece power. You will soon learn to coordinate your foot
action with the need for more power as you work. A beginner
will push the foot throttle down a set amount and try to do the
rest by pushing the handpiece harder, while never changing foot
position. This is incorrect and not a safe way to use a handpiece.
At the start of the cut, increase
power in a smooth fashion. If
you need more power, press
more with your foot. As the cut
tapers to the end, reduce the
foot pressure gradually as your
hand tilts the graver up and
out. With a little practice, this hand/foot coordination will become
as natural as driving a car.
HOW TO USE THE BIAS CONTROL
After you tune the handpiece, notice that the handpiece starts
working as you press down on the foot throttle. Add one or
two pounds of air pressure to the pressure gauge with the air
pressure dial (Fig 4-B). Now, open the bias control (Fig. 4-C)
by turning it counter-clockwise and notice that it does not take
as much pressure on the foot throttle to activate the handpiece.
The bias control allows you to adjust the foot throttle action so
you can predict the moment the handpiece will start, giving you
optimum handpiece control. This is a feature that one would use
for fine detail work such as Bulino or shading. By opening the
bias control fully you will find that the handpiece will start to work
without pressing on the foot throttle. You may find this function
useful for some operations such as stippling.
SETUP AIRTACT FOR USE
Disconnect the air supply by turning off the GraverMach AT
power switch (Fig. 8-C). Connect the larger handpiece hose to
the standard handpiece air supply port on the GraverMach AT
(Fig. 8-H). Take the smaller hose and connect it to the Airtact
handpiece air supply port (Fig. 8-F) by gently twisting the hose
end connector knob half a turn clockwise until it stops. Turn the
air supply pressure back on and check carefully for leaks.
Turn the selector knob from foot control to Airtact hand
control (Fig. 8-E).
AIRTACT AIR PRESSURE
ADJUSTMENTS
Begin by turning the power
switch on to the GraverMach
AT system and adjust the
strokes per minute (SPM) knob
to 2300 or 2400 SPM. Switch
the handpiece selector knob to
the handpiece you wish to use.
The Airtact control unit has a
regulator and gauge on the
upper face located above the
primary air pressure gauge and
bias valve. By lowering the air
pressure settings you are really
changing the range at which
the handpiece will operate. A
lower pressure setting means
that the handpiece will not
reach full power but it still has
the same operating range up
to that point. The power you
want the handpiece to have
is controlled by the pressure
applied to the touch element
on the handpiece. Using the
Airtact controls, move the small
regulator knob (Fig. 8-B) and increase the Airtact air pressure to
12 psi (0.8 bar). Now, use the primary air regulator (Fig. 4-B) by
turning it counter-clockwise until the gauge shows 5 psi (0.4 bar).
Hold the handpiece vertically next to your ear and slowly begin
to increase the air pressure by turning the primary regulator knob
clockwise. You will feel the handpiece begin to buzz, then vibrate,
and knock lightly. When the knocking stops, your handpiece is
considered tuned.
Fig. 6
Fig. 7
Hammer Handpiece
Fig. 8 • USING AIRTACT FEATURE
A. Airtact air gauge
B. Airtact regulator knob
C. On/Off button
D. Handpiece selector knob
E. Hand/foot control selector knob
F. Airtact handpiece air
supply ports
G. Strokes Per Minute (SPM) knob
H. Standard handpiece air
supply ports
C
H
F
G
D
B
A
E
