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For Machines Mfg. Since 8/09
Model SB1027
OPERATION
Setting Spindle Speed
Setting Spindle Speed Range
Setting the spindle speed range involves using a
lever to engage/disengage the spindle spline with
the bull gear.
To set the spindle speed range:
1. DISCONNECT MILL FROM POWER!
2. Use the chart below to find the spindle speed
range that includes the required spindle
speed for your operation.
Spindle Speed Ranges
Low Range 60–575 RPM
High Range 575–5000 RPM
To avoid damage to the spindle, gears, or
cutting tools:
• SpindlerotationmustbeturnedOFFand
the spindle must be at a complete stop
BEFORE you change the spindle speed
range.
• ThemillisdesignedtoONLYoperatewith
the spindle speed range selector in either
the high or low position. To avoid damaging
the moving parts inside the headstock,
never start spindle rotation without the
range selector detent pin firmly seated in
either the high or low position.
• Whenchangingthespindlespeedrange
and the direction of spindle rotation
reverses, you will need to either change
the cutting tool for the direction of spindle
rotation or use the spindle direction switch
to compensate for the change.
When the spindle speed range is changed,
the direction of spindle rotation will reverse.
ALWAYS know which way the spindle
is rotating before beginning the cutting
operation.
Using the correct spindle speed is important
for 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 mill
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 cutting tool, as noted in Figure 33:
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, provide
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 all applicable variables to determine
the best spindle speed for the operation.
Cutting Speed (FPM) x 12
*Recommended
Tool Dia. (in inches) x 3.14
= SpindleSpeed (RPM)
*Double if using carbide cutting tool
Figure 33. Spindle speed formula for milling.