Ironworkers love flap disc abrasives because they cut the middle between the finishing capabilities of a fiber disc and the bulk metal removal capabilities of a grinding wheel. Earlier this year Milwaukee released a new line of flap disc abrasives made with a “high-performance” zirconia grain that aims to increase that convenience by improving disc life.
Flap discs are made of small overlapping sheets of cloth to which grit is bound. As the wheel rotates, the sharp edges of the grit remove material. When the grain becomes dull, it fractures to expose new cutting edges. Eventually the grain fractures to the point that it’s too small to stay attached to the backing material and is ejected from the disc along with other grinding debris.
The grit used in flap disc applications commonly consists of aluminum oxide, but is often made of zirconia on higher-end discs. (The fact that aluminum oxide grit is “stronger” works against it in this application because it’s less likely to fracture.)
Milwaukee claims their “high-performance” grain improves upon standard zirconia by “micro-fracturing” — breaking off in smaller pieces when it fractures, thus maximizing the percentage of sharp grain edges exposed and keeping the particle attached to the disc longer. Milwaukee claims a 15% increase in life span over other zirconia flap discs and a 30% increase over aluminum oxide.
Milwaukee offers flap discs in both flat (Type 27, recommended for light to moderate surface removal) and conical (Type 29, recommended for moderate to heavy surface removal) form factors, and the Type 27 is also available in an extra thick configuration that yields 40% longer disc life.
Street pricing starts around $5/disc.
Press Release [Milwaukee]