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Model G0773 (Mfd. Since 12/14)
-41-
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 49. 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.
The
se sources
also provide a wealth of additional
information about the variables that affect cutting
speed and
they are a good educational resource.
A
lso, 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.
Setting Spindle Speed
Spindle speed is selected by positioning the
V-belt either between the spindle and motor pul-
leys (see Figure 50), or between the spindle and
idler pulleys. Select the motor pulleys for high
(720-2100 RPM) or idler pulleys for low (150–470
RPM) speed ranges. The V-belt diagram below is
also found on the headstock.
Refer to Tensioning & Replacing V-Belts on
Page 70 for instructions on removing and re-
installing V-belts.
Tool Needed Qty
Hex Wrench 4mm .............................................. 1
Figure 50. Belt positioned for 720 RPM.
V-Belt
Idler
Pulleys
Spindle
Pulleys
Motor
Pulleys