The cost of Cobalt over HHS is not that great but the pay back is by far greater. How many times have you picked a piece of stock up from a junk barrel not knowing what it is? Maybe its 1040 or 4140 or stainless. One slip of not cutting and the hole has work hardened. Cobalt gives that extra edge.
Northern Tool has good prices in their flyer's for small sets to letter number and fractional also McMaster Carr has the nice choice of single or multiple bits in any finish.
Uncoated (bright finish) bits are for use on carbon steel, aluminum, copper, brass, bronze, and plastic.
Black-oxide bits are for use on steel, stainless steel, and cast iron.
The best is the TiCN (titanium carbonitride) also the most expensive.
I like the black-oxide coated HSS over the shiny silver, the coating actually a lubrication to move the chips up the flutes.
dwdw47
