In article cab8b2a4-f141-4405-874a-db516a17195a@
20g2000yqt.googlegroups.com, says...
Hello All,

I had the occassion to drill through some very hard fasteners.
Standard HSS bits were becoming dull in a very short timespan, so I
opted for cobalt bits to continue.

Armed with a set of Craftsman bits, I went back to work. Not much
difference. Altering speeds, using light oil, nothing really worked.
Ended up using a Dremel tool with a cut-off disc to remove the
fastener heads (which presents other problems).

What gives?

Regards,

Ernst

Coblat isn't that much harder than HSS, they just have better high
temperature hardness. You might try repointing a masonery bit. Not
guaranteed, but it's a lot cheaper than full blown carbide drills.