Machinists have many tools we use to make holes in material, but not all holes are equal. Most of the time we use Drill Bits, which are the fastest way to make a hole, but also prone to wandering and egg-shaped holes. For more cylindrical holes we use a reamer after the drill. Reamers only cut on the side of the hole and work great for press fit connections. We can also use End Mills, tools that are shaped like flat ended drill bits. End Mills cut on the tip and along the sides, so they are also used to make holes bigger than their own diameter by rotating helically as they spin. For the highest level of precision, we make a finish cut with a boring bar, which produces straight sided, concentric holes.