126 CNC Machining
Insert Selection
There are a number of factors that help determine which insert to
use. These factors include insert grade, insert shape, insert size, and nose
radius.
Insert Grade
Carbide insert grades are based on their toughness and their ability
to resist wear. A manufacturer’s technical guide should be used to select
the proper grade needed to machine different materials. Different grades
are also based on the type of cuts being taken. Systems for grading carbide
inserts based on the insert’s application and its physical characteristics have
been developed by the American National Standards Institute (ANSI) and
the International Standards Organization (ISO).
Charts recommending the grades to be used for different machining
conditions are available from manufacturers. There are also cross-reference
charts available in catalogs to help make selections among different
manufacturers’ grades. In a case where a certain grade is not available from
one manufacturer, these charts can be used to select a similar grade from
another manufacturer.
Insert Shape
Different insert shapes accomplish specific types of machining
operations on various workpiece shapes. See Figure 6-7. The strength of
the insert also depends on the shape of the insert. For example, the round
insert has the greatest strength and the most cutting edges, while the
35° diamond insert has the lowest strength. The triangular insert is very
versatile for milling operations.
Strength increasing
Shape
Round
100° 90° 80° 80°
Trigon
60°
Triangle
55°
35°
Figure 6-7. These are the basic carbide insert shapes. Strength of the insert increases as corners
increase in angular value. The round insert is strongest. (Kennametal)