We used the DD750X sharpener on black oxide, titanium nitride, cobalt, and carbide-tipped drill bits and it worked perfectly on every material, although it did grind away the coating on cheaper bits.
I've been thinking about buying one of these but I don't know if they are just a gimmick. Also, if they genuinely work well how good do your bits need to be in the first place to be worth sharpening?
Some results have been hidden because they may be inaccessible to you
Show inaccessible results