These continuous improvements make it possible to identify a coated insert for almost any application.
Inserts sans coatings, however, still have their place.An unadorned insert with no coatings that could dull its cutting edge is often the choice when a manufacturer is faced with producing a component that has little to no room for variance from specifications from tough materials like cast iron, high-temperature materials, and heat-resistant superalloys (HRSA).
“Whether formed from high-speed steel, cobalt, or tungsten carbide, uncoated tools can be used on non-ferrous and ferrous materials,” said Harvey Patterson. “That being said, they typically work better on non-ferrous materials that create less heat and pressure, both of which deteriorate the cutting edge during the cutting process. The cutting edge pressure is dictated by the strength of the material being machined.”
Reducing that pressure, according to Patterson, is best accomplished by using tools with a positive rake. How positive depends on the material. For example, cutting aluminum will require a very high positive rake; for HRSA or titanium, the rake doesn’t need to be as high as long as the edge remains sharp to avoid placing too much pressure on the part.
