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Model G0768/G0769 (Mfd. Since 8/15)
-67-
Setting Spindle Speed
1. Rotate spindle speed dial all the way coun-
terclockwise to set spindle speed to lowest
value.
Using the correct spindle speed is important for
safe and satisfactory results, as well as maximiz-
ing tool life.
To set the mill spindle speed for operation, you will
need to: 1) Determine the best spindle speed for
the cutting/drilling task, and 2) configure the high/
low gearbox knob for the desired speed range,
3) use the spindle speed dial and spindle speed
RPM display to get the spindle speed.
Determining Spindle Speed
Many variables affect the optimum spindle speed
to use for any given operation, but the two most
important are the recommended cutting speed
for the workpiece material and the diameter of
the cutting tool, as noted in the formula shown in
Figure 113.
Cutting speed, typically defined in feet per minute
(FPM), is the speed at which the edge of a tool
moves across the material surface.
A recommended cutting speed is an ideal speed
for cutting a type of material in order to produce
the desired finish and optimize tool life.
The books Machinery’s Handbook or Machine
Shop Practice, and some internet sites, pro-
vide excellent recommendations for which cutting
speeds to use when calculating the spindle speed.
These sources also provide a wealth of additional
information about the variables that affect cutting
speed and they are a good educational resource.
Also, there are a large number of easy-to-use
spindle speed calculators that can be found on
the internet. These sources will help you take into
account the applicable variables in order to deter-
mine the best spindle speed for the operation.
Cutting Speed (FPM) x 12
*Recommended
Tool Dia. (in inches) x 3.14
=
Spindle
Speed
(RPM)
*Double if using carbide cutting tool
Figure 113. Spindle speed formula for mill/drills.
Spindle Speed
2. Rotate high/low gearbox knob (see Figure
114) to either “L” (spindle speeds 50–100
RPM) or “H” (spindle speeds 100–2000
RPM).
Note: When switching between gears, it may
be necessary to rotate spindle by hand so
gears will align and engage.
Gearbox Knob
L
(Low)
H
(High)
CENTER
(Neutral)
Figure 114. High/low gearbox knob set to low
"L".
Gearbox
Knob
3. Press ON button and turn spindle direction
switch to "F".
4. While watching RPM display, rotate spindle
speed dial clockwise until desired RPM is
reached.