Guide written by:
Sebastian, self-taught DIY-er, Exeter
Drill bits are to drills what blades are to saws: you can’t achieve much without them! There are a number of different bit types depending on the material you want to work on. Metal, masonry and wood can all be drilled with the use of specially designed bits. It is even possible to cut through glass or tiles using bits with diamond or tungsten carbide tips. The quality of drill bits is determined by the material used to make them which, in turn, controls their ability to drill into different materials. A commonly used material for drill bits is high-speed steel (HSS) used with different combinations of carbide, titanium, cobalt and so on.
The drill bit shank also comes in various formats, depending on the drill chuck used.
Masonry and metal drill bits are twisted while wood bits can be twisted or flat. The twists, or flutes, of a drill bit, may also vary to allow for better removal of the drilled material. Further variations of drill bits include adjustable bits, Forstner bits, step or cone bits, and installer bits. They all come in different diameters and lengths. Extensions can also be used to increase the length of wood bits.
Drill bit type
Drill bit material
Masonry drill bit
Straight shank, SDS+, SDS Max
From***to**** (according to percentage)
2 cutting edges
Concrete - Reinforced concrete - Breezeblock - Stone
3 cutting edges
4 cutting edges
Metal drill bit
Straight and hex shank
Rolled steel (standard use) or ground steel (frequent use)
Ground drill bit
Ground drill bit
Ferrous and non-ferrous metals - Stainless steel, etc.
Ground drill bit
Wood drill bit
Straight and hex shank
Flat drill bit
Tile drill bit
Tile - Ceramic - Roof tile
Glass drill bit
In order to select the right metal drill bit, you must first consider the type of metal you plan on drilling.
While all metals vary in weight, they also feature different levels of density that determine their hardness and resistance to drilling. For instance, lead is heavier than aluminium, but aluminium is a slightly harder metal. The density of a metal dictates the design of the drill bit as the bit must be harder than the metal it aims to drill into. When it comes to metal drill bits, one that can easily bore a hole in aluminium won’t make a scratch on an iron-carbon alloy.
With this in mind, metal drill bits are made of different materials and contain various elements, which are selected to enhance hardness and improve cutting ability. There are two main categories of metal drill bit:
Metal drill bits are categorised by their type, cutting method and, in the case of carbide bits, their binding element.
High-speed steel is the most commonly used alloy steel for metal drill bits. HSS bits feature a high level of hardness, are highly resistant and can be sharpened.
Cobalt, combined with an alloy steel like HSS (usually 5%), offers strength and resistance, and increases the hardness of the bit. Cobalt retains its properties at a higher temperature than titanium, meaning you can drill at a higher speed.
Titanium-coated HSS bits provide a stronger and more resistant alloy. Nonetheless, it’s worth remembering that the element content of metals is measured as a percentage. There is no such thing as a ‘titanium bit’ and a few microns of titanium won’t necessarily improve the quality.
Tungsten carbide lends an increased level of resistance and high hardness to drill bits. It is formed by a combination of tungsten and carbon, a very dense alloying element. This sintered compound can produce a harder or softer metal, depending on the percentage of carbon it contains.
Metal drill bits should be used with a cutting fluid, at low speeds using even and constant pressure. The metal bit should be sharpened appropriately and regularly. Even the most expensive and strongest metal drill bits will have a lifespan of just a few holes if used incorrectly.
Different mix ratios will generate metals with different properties. A low percentage (indicating a thin coating) will have little impact on the quality and resistance of drill bits. The quality of a drill bit is also affected by its treatment and manufacturing processes.
Several units of measurement are used to assess the hardness of a steel. The Brinell scale is often used with resistance measured by Newtons per square millimetre (N/mm²); the higher the number, the more resistant the drill bit.
HSS metal drill bits feature a helical or twisted shape and come in various materials providing different degrees of hardness and durability.
HSS-Gbits are ground at the tip and along their flutes. The material of these bits is ground directly into shape with the use of a grinder. They are easy to spot as their cutting edges (flutes and lips) are white rather than grey and are perfectly symmetrical. Ground bits are suitable for sustained use and are efficient and precise.
HSS-R bits feature roll-forged flutes. These drill bits are formed by a heated rolling process by which the material is shaped between two parallel cylinders turning in opposite directions. HSS-R drill bits are suitable for multiple drilling tasks and offer high precision.
Metal drill bit Ø 10mm
Non-ferrous metals, grey cast iron
Alloy and non-alloy steel, non-ferrous metals, grey cast iron and malleable iron, sintered iron
From 1000 to 1100 N/mm²
Soft metals, non-ferrous metals
Titanium (titanium nitride)
Approx. 1000 N/mm²
Alloy and non-alloy steel, malleable iron, sintered iron, non-ferrous metals
Cobalt (0.5 or 0.8%)
From 1000 to 1200 N/mm²
Hard and treated steels; stainless steel, chrome nickel, cast iron and bronze
From 1200 to 1500 N/mm²
All alloy and non-alloy steel, ferrous and non-ferrous metals
Selecting a masonry bit is more straightforward given that your decision basically comes down to how soft or hard the drilling material is. Most masonry drill bits are made from tungsten carbide which further simplifies your decision.
Tungsten carbide drill bits work efficiently on concrete, granite, sand-lime brickwork and natural stone. The overall quality of concrete drill bits depends on the quality of their point and the number of cutting edges they feature (two, three or four).
For optimum efficiency when working with harder materials and reinforced concrete, a point with four cutting edges in solid carbide must be used. Lower quality drill bits generally only have two cutting edges. Drill bits made from other materials (for example, diamond bits) are more useful for drilling glass, tiles, ceramic, and so on.
Reinforced concrete or breezeblock should be drilled in hammer mode with a standard or hammer drill. Three types of shank are used for drilling concrete:
Some drill bits feature hex shanks, such as those used for electric screwdrivers. These drill bits are designed for use with screwdriver tools with a hammer mode.
Concrete drill bits also feature different flute designs in order to facilitate dust removal.
The four main flute designs seen in masonry drill bits are:
The flute design is directly linked to the quality of the point and the number of cutting edges the bit features. You do not necessarily have to choose the flute design: it simply comes as a result of these two factors.
Choosing a wood bit is easy: you simply have to decide between a flat bit or a twist bit. Most wood bits are made of tempered steel.
It should also be noted that twist bits are more appropriate for drilling thicker materials (such as a wooden post, for example), while flat bits should be used for shallower materials.
Like metal drill bits, wood bits can feature different shank types – the most common being the straight shank.
In addition to the many variations of metal, concrete and wood drill bits, a range of drilling accessories may also prove useful.
Guide written by:
Sebastian, self-taught DIY-er, Exeter, 235 guides
Redo a roof with wooden beams? Check.Advise Mister everybody in the DIY shop? Check.Redo the bathroom plumbing? Check.Fit together, build the walls, paint a partition, throw my hammer in a rage thinking that it will fix the problem? Check. The DIY motto ? Learning is better than delegating… well, it's also a question about your wallet! The satisfaction? The beer at the end of the job! What do the best have in common? The influence of Gyro Gearloose, Mac Gyver and Carol Smiley depending on your generation, a good dose of curiosity, a average hand-eye coordination and a taste for risks… and if it doesn't work, try again! Advise you? I'll do my best!