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Model G0773 (Mfd. Since 12/14)
Setting Spindle Speed
1. Set Lathe/Mill selector switch to 2 for milling
operations (see Figure 94).
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) use the spindle
speed dial to obtain 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 93.
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 93. Spindle speed formula for mill/drills.
Spindle Speed
Figure 94. Location of lathe/mill selector switch.
2. Rotate variable-speed dial (see Figure 95)
clockwise to select mill speed from 100–
2500 RPM. Rotate dial further clockwise
to increase speed or counterclockwise to
decrease speed.
Figure 95. Location of milling head variable-
speed dial.
Variable-Speed Dial
Lathe/Mill
Selector Switch