Review on Irwin Unibit2T Titanium Nitrate 16 Inch: Ultimate Drilling Power with Enhanced Durability by David Golden

Not new to step drill bits, I bought this to make shallow holes in mild steel plate. It has deeper steps, ostensibly to drill deeper holes in the material, and since it's cobalt I assumed it was metalworking grade. I was wrong and lucky to get 10 holes. I would limit this to aluminum and other softer materials and not expect sound holes to go into anything more durable. By the way, the racquet literally splintered because of the hard cobalt steel, so wear safety goggles!