How to Choose the Right Drill Bit for the Material

Most miserable drilling experiences begin with the wrong bit, too much speed, too much pressure, or all three at once.

Wood

Standard twist bits work for many small holes in wood. Brad-point bits help start accurately and can leave cleaner edges. Spade bits are fast for larger rough holes, while Forstner bits make cleaner flat-bottomed holes and are useful when appearance and control matter.

Metal

Use a sharp high-speed-steel or appropriate cobalt bit for common metals. Start with a center punch where possible so the bit does not wander. Lower speed and controlled pressure are generally better as diameter increases. Cutting fluid may improve tool life and finish depending on the metal and application.

Masonry

Masonry bits use a carbide tip designed for concrete, brick, and similar material. A hammer drill makes many masonry jobs dramatically easier, but the material and fastener system determine the correct bit diameter and depth.

Tile

Tile can require spear-point carbide, diamond, or other specialty bits. The technique depends heavily on the tile material. Avoid uncontrolled hammer action on brittle tile surfaces unless the manufacturer and method call for it.

Hole saws and step bits

Hole saws are useful for large circular openings in wood, drywall, and—using the correct type—metal. Step bits are particularly handy for enlarging holes in sheet metal and thin material.

Speed, heat, and pressure

If a bit is smoking, turning blue, or polishing the work without cutting, stop. Excessive speed creates heat, and excessive pressure can chip cutting edges or overload the drill. Sharp tools should make chips; they should not need a wrestling match.

Match the hole to the fastener

Anchors, screws, taps, rivnuts, and other fasteners specify hole sizes for a reason. Measure the bit if markings are unreadable and follow the fastener manufacturer's instructions rather than choosing the bit that “looks about right.”