Spindle Speed - Grizzly G4003G Owner's Manual

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.
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 workpiece, as noted in the formula shown in
Figure 59.
*
Recommended
Cutting Speed (FPM) x 12
Dia. of Cut (in inches) x 3.14
*
Double if using carbide cutting tool
Figure 59. Spindle speed formula for lathes.
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.
Model G4003G (Mfd. Since 1/15)
Setting Spindle Speed
The alpha and numeric spindle speed levers,
shown in Figure 60, are used to select one of the
nine spindle speeds.
The spindle speed levers control the gear configu-
ration in the headstock to produce the selected
spindle speed.
Spindle
Speed
=
(RPM)
The chart below shows the various combinations
of lever positions for achieving a desired speed.
Alpha
Lever
Figure 60. Spindle speed levers.
To avoid damaging gears, ALWAYS make
sure the spindle is completely stopped
BEFORE moving the spindle speed levers.
I
270
A
70
B
200 1000 600
C
Figure 61. Spindle speed chart.
Numeric
Lever
II III
1400 800
360 220
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