Model G0782 (Mfd. Since 10/15)
-45-
Spindle Speed
Cutting Speed (FPM) x 12
*
Recommended
Dia. of Cut (in inches) x 3.14
Spindle
Speed
(RPM)
*
Double if using carbide cutting tool
=
Figure 56. Spindle speed formula for lathes.
Determining Spindle Speed
Using the correct spindle speed is important for
getting safe and satisfactory results, as well as
maximizing 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 lathe
controls to produce the required 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
workpiece, as noted in the formula shown below.
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.
Figure 57. Location of spindle speed and spindle
speed range levers.
Setting Spindle Speed
The spindle speed lever and spindle speed range
lever, shown in
Figure 57, are used to select one
of the eight spindle speeds.
To avoid damaging gears, ALWAYS make
sure the spindle is completely stopped
BEFORE moving the spindle speed levers.
The chart below shows the various combinations
of lever positions for achieving a desired speed.
70
115
300
755 460
2000
1255
190
Spindle Speed RPM
X
min
Spindle
Speed
Range
Lever
Spindle
Speed
Lever
The spindle speed and range levers control the
gear configuration in the headstock to produce
the selected spindle speed.
Spindle Speed
Range Lever
Spindle Speed
Lever
Figure 58. Spindle speed chart and applicable
spindle speed and range lever positions.
Summary of Contents for G0782
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