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G0619 DELUXE SMALL MILL/DRILL
-21-
Calculating Spindle
RPM
Closely follow the proper cutting speed and prop-
er feed to reduce undue strain on all moving parts
and increase operator safety.
Prior to milling, determine the RPM needed to
cut your workpiece, then set the RPM on the
machine.
To determine the needed RPM:
1. Use the table in Figure 19 to determine the
cutting speed required for the material of your
workpiece.
2. Measure the diameter of your cutting tool in
inches.
3. Use the following formula to determine the
needed RPM for your operation:
(Cutting Speed x 4) /Tool Diameter = RPM
Cutting Speeds for High Speed Steel (HSS)
Cutting Tools
Workpiece Material Cutting Speed (sfm)
Aluminum & alloys 300
Brass & Bronze 150
Copper 100
Cast Iron, soft 80
Cast Iron, hard 50
Mild Steel 90
Cast Steel 80
Alloy Steel, hard 40
Tool Steel 50
Stainless Steel 60
Titanium 50
Plastics 300-800
Wood 300-500
Note:
For carbide cutting tools, double the cut-
ting speed. These values are a guideline only.
Refer to the MACHINERY'S HANDBOOK for
more detailed information.
Figure 19. Cutting speed table for HSS cutting
tools.