A step drill bit, also known as a speed bit, or Unibit is a conical shaped drill bit with a steps cut into the sides. Due to the design of a step drill a single bit can be used for drilling a number of different hole sizes. Some step drill bits come to a point and are therefore self-starting. The larger-size bits have blunt tips and are used for hole enlarging.

Step drill bits are most commonly used on softer materials - plywood, particle board, drywall, acrylic, laminate, etc. They can be used on very thin sheetmetal, but metals tend to cause premature drill wear and dulling. A metal hole saw is more appropriate for large-hole applications in thicker metals. .