Figure 5-12.--Three causes of tool breakage.
most likely will occur when an inadequate amount of
that determine grade include hardness, toughness, and
coolant is used. If you can't keep the work and tool
flooded with coolant, it's usually better to machine
of carbide tools may vary by the percentages of cobalt
and titanium or tantalum carbides. Properties may
also vary during the processing by the grain size of
carbides, density, and other modifications. Some
tungsten carbide inserts are given a titanium carbide
The following list shows some of the things you
coating (about 0.0003 in. thick) to help them resist
can do to overcome the problems of tool edge
cratering and edge breakdown.
The grades of carbides have been organized
according to their suitable uses by the Cemented
If edge wear occurs:
Carbide Producers Association (CCPA). When you
Decrease machining speed.
select a carbide, use a table made up of those suitable
uses rather than make your choice based on
Change to a harder, more wear-resistant
c a r b i d e grades with specific chip removal
If the cutting edge is chipped or broken:
Roughing cuts (cast iron and nonferrous
General purpose (cast iron and nonferrous
Decrease feed and/or depth of cut.
Change to a tougher grade carbide insert.
Light finishing (cast iron and nonferrous
Use negative rake.
Precision boring (cast iron and nonferrous
Hone the cutting edge before use.
Check the rigidity and tooling overhang.
Roughing cuts (steel)
When there is buildup on the cutting edge.
General purpose (steel)
Finishing cuts (steel)
Precision boring (steel)
Change to a positive rake tool.
The hardest of the nonferrous/cast iron grades is
Change to a grade containing titanium.
C-4 and the hardest of the steel grades is C-8. This
Increase the side cutting edge angle.
system does not specify the particular materials, alloy,
or machining operations. It combines experience
gained from using carbides and manufacturer's
CEMENTED CARBIDE GRADES.--Cemented
recommendations to select the proper grade of
carbides have been organized into grades. Properties