Are cobalt drill bits solid throughout, or just coated?
Titanium bits are just coated, so if you sharpen them, they’re not as good as new. Are cobalt bits the same way, or are they made of a homogeneous substance rather than being coated. I want some good metal drilling bits, but I won’t invest in cobalt if I can’t resharpen them w/ a Drill Doctor. Please give a reference, if you can, as well as any personal experience w/ good bits. Well so far I’ve got one answer either way, but neither with a source to corroborate. At least I’m getting some other good info. Drill Doctor may not be optimal, but I can’t see myself trying to sharpen smaller bits manually with a grinder. Cobalt Drills are not coated. They maintain their hardness throughout and can be resharpened without loss of hardness. Stay away from the imports. I have found that the best cobalt and HS Drill Bits are Cleveland Twist Drills. Also, I’m not a big fan of the Drill Doctor. With a little practice you can achieve better results sharpening them by hand on a Bench Grinder.
