Both solid-carbide and small indexable-insert ballnose endmills are capable of the speeds and feeds required for high-speed finishing of molds. Moldmakers should keep in mind, however, that the indexable-insert tools offer important cost advantages – starting with a much lower replacement cost and no regrinding.

Solid-carbide endmills are very expensive. When they break, the entire tool must be replaced at new-tool cost. By contrast, a broken insert on an indexable-insert endmill can be replaced for just a few dollars.

The indexable-insert cutters also eliminate the need for regrinding, which is labor-intensive and very costly. Regrinding also results in a loss of tool diameter size. In some moldmaking operations, that can mean the added cost of an extra finishing pass to meet critical dimensional requirements.

Broad versatility is another cost advantage of the indexable-insert endmills. In many cases, only a simple change of insert grade or geometry is needed to equip the same cutter body for use in a variety of moldmaking applications and materials.

For all of their cost advantages, however, today’s indexable-insert ballnose endmills also provide the high speed and feed capabilities needed for productive high-speed finishing of molds. By using PVD-coated micrograin carbide inserts, the cost-saving indexable cutters are routinely run at cutting speeds of 10,000 sfpm and feeds of 300 ipm, while taking 0.010 inch axial and 0.010 inch radial depths of cut on molds or dies hardened to 55 Rockwell C. The operations typically produce surface finishes of 25 microinches or better.