The objective of this most recent product development for HSS core drills was to produce a range of core drills optimised for power with greater heat resistance and better protection against wear. The desired results were achieved by an enhanced proportion of cobalt in special steel. Combined with speed-controlled BDS magnetic core drilling machines, these core drills are adapted for high loads in fine-grained steels and rust-proof materials. The core drills can be reground whilst retaining their positive productHSS Cobalt 8% core drills are made from M 42 steel.
M42 is a molybdenum-series high-speed steel alloy with an additional 8% or 10% cobalt. It is widely used in metal manufacturing industries because of its superior red-hardness as compared to more conventional high-speed steels, allowing for shorter cycle times in production environments due to higher cutting speeds or from the increase in time between tool changes. M42 is also less prone to chipping when used for interrupted cuts and costs less when compared to the same tool made of carbide. Tools made from cobalt-bearing high speed steels can often be identified by the letters HSS-Co. (Source: Wikipedia)
HSS Cobalt 8% Core drills are http://crochetedbuddies.com/product/B00MNA0PLE/US/shmyje-20/page/2/?cart=y Harder, Stronger, Have more service life, Make more holes per cutter, etc.