
226 Fundamentals of Machining Processes
contains 95% SiC, and green, which contains 98% SiC. They are also used for
sharpening carbide-tipped cutting tools and for dressing grinding wheels as
a substitute for diamond.
Boron carbide (B
4
C): It has a hardness that approaches that of diamond. It is
brittle and expensive and is used for lapping cemented carbide tools, cutting
precious stones, and grinding high-hardness cutting tool materials.
Cubic boron nitride (CBN): Its properties are similar to that of diamond and
have a high resistance to heat. CBN wheels are used for machining extra hard
materials at high speeds. It is 10–20 times more expen