How to choose the right drill bit: guide to sizes and materials

An unsuitable drill bit is the #1 cause of DIY failure: slipping bit, breakage, chips, or a hole too big or too small for the anchor. Learning to choose the right drill bit is the basis of successful drilling. This guide explains everything, simply.

The different types of drill bits

Masonry drill bit (or hammer drill bit)

Recognizable by its carbide tip (metal insert at the end), it drills concrete, brick and cinder block. Use it in hammer mode on a drill/driver, or with a rotary hammer for large diameters.

Wood drill bit

Its center point (brad point) guides it through wood without wandering. It comes in a standard version or as a wood auger bit (round-shank auger). Never use it on concrete: it would dull immediately.

Steel / metal drill bit (HSS)

Made of high-speed steel (HSS), it drills metal, aluminum and stainless steel (for stainless steel, choose a cobalt HSS-Co bit). Use it at slow speed with a little lubricant to cool it.

Tile drill bit

With a cross point or diamond tip, it drills ceramic, stoneware and porcelain at low speed, without hammering.

What diameter for which anchor?

The golden rule: the drill bit must have exactly the diameter of the anchor. This diameter is always indicated on the anchor packaging. Common examples:

• 5 mm anchor → 5 mm drill bit (light loads)
• 6 mm anchor → 6 mm drill bit (standard shelf)
• 8 mm anchor → 8 mm drill bit (medium load)
• 10 mm anchor → 10 mm drill bit (heavy loads: TV, furniture)

The length of the drill bit

The drill bit must be longer than the anchor, because it drills the hole into which the entire anchor must fit. For a 40 mm long anchor, use a drill bit of at least 60 mm (anchor + 20 mm of safety).

Drilling mode: which setting?

• Concrete, cinder block, solid brick → hammer mode
• Hollow brick, tile, drywall → drilling mode only (without hammer)
• Wood, metal → drilling mode only

Frequent mistakes to avoid

• Using a masonry bit on wood (drills fast but tears)
• Using a wood bit on metal (breaks immediately)
• Drilling tile in hammer mode (cracks the glaze)
• Forcing on a dull bit (breaks and overheats)
• Using a bit that is too short for the anchor