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Model G0779 (Mfd. Since 09/14)
-25-
Using the correct spindle speed is important for
safe and satisfactory results, as well as maximiz-
ing tool life.
To set the spindle speed for your operation, you
will need to: 1) Determine the best spindle speed
for the cutting task, and 2) configure the spindle
speed levers to produce the required 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 22.
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 22. Spindle speed formula for drills.
Spindle Speed
Setting Spindle Speed
Use the chart below or the one on the headstock
when setting the spindle speed.
Spindle Speed Range Lever Speed Lever
90 RPM L 1
210 RPM L 2
345 RPM L 3
670 RPM H 1
1180 RPM H 2
1970 RPM H 3
Change spindle speed ONLY when the
spindle is completely stopped. Otherwise,
machine damage could occur.
With the spindle completely stopped, position the
spindle speed selectors (see Figure 23) to set the
spindle speed.
Note: If necessary, rotate the spindle by hand to
mesh the gears when changing speeds.
Figure 23. Spindle speed controls.
Spindle
Speed
Chart
Spindle Speed
Range Selector
Spindle Speed
Selector