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How to Choose the Right Drill Bit for Metal, Wood, Tiles, Glass or Masonry

Eugene is a trained engineer and self-taught home improvement enthusiast with almost 40 years of professional and DIY experience.

A HSS drill bit for drilling steel

A HSS drill bit for drilling steel

Boring a Hole: Picking the Best Drill Bit for the Job

When drilling any material, the correct bit is essential so that holes can be bored quickly and with ease. If you are a newbie at DIY, this article explains how to go about choosing the right drill bit for the job when boring through various materials such as metal, masonry, plastics, wood, glass, and tiles. I outline some tips for drilling, the proper way to use a hand power drill, and how drill bits can be sharpened. At the end of the article, you'll find an 11-minute video that shows you how to drill.

Which Drill Bit for Steel or Other Metals?

  • HSS
  • Titanium coated or cobalt steel
  • Metal hole saw
  • Unibit (step bit)

HSS Bits

HSS or high-speed steel bits are made from carbon steel with the addition of other elements such as chrome and vanadium. This allows them to be used at high drilling speeds. HSS bits can be used to drill iron, steel and other metals such as brass, copper and aluminum alloy. They can also be used to drill plastic. You can drill wood with an HSS bit if nothing else is available, however, if the hole is deep or of large diameter, the bit will become excessively hot and drilling progress will be slower.

HSS dril bit

HSS dril bit

Titanium Coated or Cobalt Steel

HSS bits with a coating of a titanium compound are more durable and harder than HSS bits, and suitable for drilling hard materials, e.g. stainless steel. In practice though, the titanium coating eventually wears away, and if you sharpen them with a drill bit sharpener or by hand, the coating is totally lost. Titanium bits look like HSS bits with a brass or orange coloring.

Another option for drilling hard steels or stainless steel are cobalt alloy bits. They are manufactured from solid alloy, not just coated like titanium bits, and sometimes marked HSS Co. The addition of cobalt makes the drills more durable and they can withstand higher temperatures during drilling without losing their edge. The disadvantage is that they are more expensive, more brittle and therefore more likely to chip at the cutting edge. Cobalt steel bits can, of course, be used for drilling "normal" mild steel or other metals.

Step Bit (Unibit)

Step bits are conical shaped with a multiple of cutting edges of varying diameters. They are suitable for drilling thin softwoods, laminates (e.g. plywood) and particle board (chip board), plastics, drywall (plasterboard) and sheet metal. Step bits are ideal for electrical work when varying sized holes have to be cut in junction boxes, panels, etc. The advantage of this type of bit is obviously the convenience of being able to drill a variety of hole sizes without changing bits. Also because the bit generally comes to a point, a pilot hole isn't required as is usually the case if a large hole needs to be drilled.

Drill and Driving Bits Set by Craftsman

This 100 piece drilling and driving set by Craftsman includes all the necessary drill bits for boring holes in wood, plastic, metal and masonry. Ideal for general purpose DIY work around the home, crafts and hobbies. It also has a comprehensive set of driver bits and nut drivers for use with a cordless drill.

Drill and driving set.

Drill and driving set.

Which Drill Bit for Wood?

  • Spade or flat wood bit
  • Lip and spur (Brad Point) bit
  • Hole saw
  • Masonry bit
  • Step bit
  • HSS bit if nothing else available

Spade or Flat Wood Bit

These are suitable for rapid drilling through wood and are commonly available in sizes from 1/4 inch (6 mm) to about 1 1/2 inches (36 mm). The disadvantage of spade bits is that they can produce a splintering effect as the bit emerges from the timber, if you apply too much pressure.

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Lip and Spur (Brad Point) Bits

These are another option for drilling timber and are available in sizes from 1/8 inches (3 mm) to 5/8 inches (16 mm). They can also be used for drilling soft plastic and are less likely to cause melting of the edges of the hole due to friction, which can happen when drilling with an HSS bit.

Quick release clamps are useful for holding a length of timber during drilling

Quick release clamps are useful for holding a length of timber during drilling

Hole Saws

Drilling very large holes greater than 1 1/2 inches with a standard bit is impractical as you would need a drill with a huge amount of power and torque to overcome friction in order to drill through timber. Instead, drilling large holes can be accomplished with a hole saw. This has small teeth like a handsaw and the "blade" is in the form of a cylinder. Some hole saws are only designed for drilling wood or plastic while other versions are made from HSS steel and suitable for drilling iron, steel and other metals in addition to wood.

Which Drill Bit for Plastic?

You can use the same bits as for wood. However, drill slowly. If you drill fast, friction can rapidly cause plastic to melt, clogging the tip and flutes of the drill with melted shavings, especially if the bit is blunt. As shavings cool and get stuck in the flutes, or coat the bit, the problem gets worse and the bit can get stuck. It's not such a big deal when drilling through thin plastic, but I've found that when drilling through thicker sheets and specifically acrylic (commonly known by the brand names "Plexiglass" or "Perspex"), this can be a problem. The same goes for cutting this plastic with a jigsaw, use a slow speed.

Which Drill Bit for Brick, Solid Concrete, Block (Masonry)?

  • Tungsten carbide bit
  • Diamond hole saw

Tungsten Carbide Masonry Drill Bits

These type of bits are used for drilling holes in stone, solid concrete, concrete blocks, brick, and breeze blocks (aerated concrete blocks). They are available in sizes from just under 1/4 inches (5 mm) to 1 1/2 inches (approx. 40 mm).

Masonry bits are available with a round section shank for use in a conventional chuck. However, a better choice is an SDS type bit. The shank on this type of bit doesn't slip in a chuck and can be quickly inserted and extracted from the SDS chuck on the power drill. Masonry bits are used in what is known as an impact, hammer or percussion drill. This percussive or hammering action pulverizes the masonry in contact with the tip of the bit.

Masonry bits can be used for drilling rough holes in timber. However, the hole will be rougher and progress slower. This is because the drill just chips its way by brute force through the wood. A proper wood drill bit shaves its way through timber like a chisel. For construction work though, this isn't an issue.

Wall plugs fixings (sometimes called "Rawlplugs"), allow cupboards, brackets etc. to be attached to concrete walls.  The max and min size screw is indicated. A tungsten carbide bit is used for making holes.

Wall plugs fixings (sometimes called "Rawlplugs"), allow cupboards, brackets etc. to be attached to concrete walls. The max and min size screw is indicated. A tungsten carbide bit is used for making holes.

Diamond Core Bits

These are similar to hole saws but used for drilling large holes in concrete or aerated cement blocks.

Which Drill Bit for Glass and Tiles?

  • Spear head bit
  • Diamond bit

Spear Head Bits

These are made from tungsten carbide and suitable for drilling glass or tiles. When drilling glass, if possible lay it flat on a soft cloth or newspaper for support. Drill at low to medium speed and either spray the area being drilled with water to cool and lubricate the bit, or make a "dam" of plasticine around the area and fill it with water.

Drilling Tip:
A piece of PVC insulating tape stuck on glass or tiles stops the bit from wandering and slipping on the surface.

Spear point glass drill bit

Spear point glass drill bit

Diamond Tipped or Coated Bits

These are used for drilling tiles and glass. However, they only have a limited lifespan before the coating of grit wears away.

Are There Different Types and Sizes of Chucks?

The chuck on a cordless drill is usually either 10 mm (3/8 inch equivalent) or 13 mm (1/2 inch). Lower voltage drills (e.g. 12 volts) tend to be fitted with a 10 mm chuck.
Corded drills usually come with a 13 mm chuck as standard, but 16mm (5/8 inch) chucks are also available. Drills bits with a diameter larger than 13 mm normally have a reduced diameter shank so that they can be inserted into a 13 or 16 mm chuck. SDS chucks also come in various different sizes, but the 10 mm SDS-Plus type is the most common version encountered on DIY/ low powered professional SDS power drills.

For more information on chuck sizes and choosing corded and cordless drills, see my guide: A Complete Guide to Power Tools, Corded & Cordless (Drills, Sanders, Grinders, Multitools, Dremels & Saws)

Clockwise from top: Chuck key, keyed chuck, SDS chuck, keyless (hand tightened) chuck

Clockwise from top: Chuck key, keyed chuck, SDS chuck, keyless (hand tightened) chuck

Drill Bit Sizes

Drill bits are available in metric (mm) and Imperial (inch) sizes. HSS drill bits range from 1mm (3/64") to over 25 mm (1"), although smaller diameter bits are available for specialist applications. Bits greater than 13 mm diameter generally have a reduced diameter shank so that they can fit in a 13 mm chuck.

Measuring the Diameter of a Drill Bit

Normally the size is stamped or engraved on the shank of a bit. Unfortunately manufacturers insist on placing the marking near the end of the shank, so it can get worn off over time if a round profile shank slips in a chuck. So you can end up with a lot of unknown size bits in your collection. You can roughly measure the diameter of a bit with a tape or ruler, but a vernier or electronic calipers is the proper tool for the job. You can also use it for measuring thickness of materials, internal hole diameters and general purpose measuring. Resolution is normally about 0.05 mm or 2 thousandths of an inch. You can buy a purely mechanical vernier calipers, which has a vernier scale. Alternatively an electronic calipers displays the result on an LCD scale which can be read directly. The advantage of an electronic calipers is that the display can be read directly, switched between imperial (inch) and metric and the jaws can be zeroed to cope with any drift or wear.

Vernier calipers top and electronic calipers bottom

Vernier calipers top and electronic calipers bottom

This Neiko electronic calipers is recommended as a best buy by Amazon. It has a higher than normal resolution of 0.001 inch (one thousandth) or 0.01 mm and three measuring modes, mm, inch and fractions of an inch. The LCD display is extra large and the body is manufactured from stainless steel (cheap calipers are made from plastic). Currently it retails at $22.43 with free Prime shipping.

what-drill-bit-to-use

How to Hold a Power Drill

Hold the drill with the trigger handle horizontally in the "3 o'clock" position and the side handle in the "12 o'clock" vertical position. If the drill bit sticks, the power drill will turn violently counterclockwise, the side handle will get pushed into the palm of your hand and you may just about be able to hold it before you release the trigger. If you hold both handles in the "6 o'clock" position i.e. pointing vertically down, the side handle of the drill may pull out of your hand. This will almost certainly happen if it is a high power drill without a safety slip chuck. In any case, hold a drill tightly and brace your arms, ready for the unexpected.

Holding a power drill correctly