Abrasive Types
There is a wide selection of abrasives to choose from when selecting a lapping and polishing process. Selecting an
abrasive is dependent upon the specimen hardness, desired surface finish, desired removal rate, lifetime, and price.
There are four basic types of abrasives that are used in lapping and polishing processes: silicon carbide (SiC),
aluminum oxide or alumina (Al2O3), boron carbide (B4C), and diamond (C). All of these abrasives have distinct
properties and are used for different materials and applications.

SiC: SiC is hard and generally has a needle or blocky structure. SiC is used in many applications where
rough lapping is required. It seldom is used for polishing or applications that require smooth surface
finishes.

Al2O3: Al2O3 is relatively hard and has a sharp, angular structure. Alumina is commonly used where fine
surface finishes are required as it breaks down over time and gives excellent surfaces during lapping
and polishing. Alumina is also relatively inexpensive.

B4C: B4C is harder than most other abrasives (excluding diamond) and has a blocky crystal structure. B4C
provides excellent removal rates and is typically used when fast removal with moderate surface quality
is needed.

Diamond: Diamond is the hardest material known and has a sharp, angular structure. Diamond is extremely
useful in lapping and polishing due to it’s removal rates and surface finishing qualities. Diamond can
produce excellent surface finishes combined with high removal rates.