Review on Titanium Nitride Coated Drill Piece by Marcus Zimmerly

Absolute rubbish. Doesn't cut steel at all. Bought to drill out a broken bolt deep below the surface. In preparation, I drilled a pilot hole with a conventional drill and filled it with cooling lubricant - a great thing, by the way. Throw the left drill 3/8 and set the drill backwards. It moved slowly and with a lot of pressure on the drill and hardly made any chips.