124 CNC Machining
• Do not remove chips by hand because of their high temperature and
sharp edges.
• Do not use an air hose to blow chips from the machine or your clothing.
• Keep tool overhang to a minimum to avoid tool chatter and possible
insert breakage.
• Take extreme care to ensure both the tool and workpiece are tight and
secure.
• Keep cutting fluids clean to avoid the possibility of foreign particles
interfering with the workpiece finish.
• To avoid the possibility of igniting the coolant because of high
temperatures generated during cutting, select the proper coolant and
use sharp tooling.
• Do not overload the carbide inserts with excessive pressure; this could
lead to insert breakage.
• Be careful when machining aluminum, magnesium, and titanium;
they represent a potential fire hazard.
• Always use the largest size tooling available.
Cutter Selection
There are a number of factors to consider when selecting a cutter. These
factors include cutter size, insert entry angle, milling cutter pitch, and lead
angles.
Cutter Size
The size of the workpiece best determines the size of the cutter that
should be used. A rule of thumb is that the cutter should be approximately
one and one-half times the width of the workpiece. If the width is greater
than any cutter size available, multiple passes should be made. With
multiple passes, one-fourth the width of the cutter body should be outside
the workpiece when making the first pass.
Insert Entry Angle
A negative entry angle is recommended to absorb the shock of the insert
entering the cut. The strongest part of the insert is near the cutter body. A
positive entry causes the tip of the insert to absorb the shock of entry. This
could lead to the insert breaking.
Milling Cutter Pitch
Cutter pitch refers to the number of inserts found on a milling cutter.
A coarse pitch is used for general-purpose milling where maximum depth
is required and adequate horsepower is available. A medium pitch is used