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Drill bits buying guide

Guide written by:
Sebastian, self-taught DIY-er, Exeter

Sebastian, self-taught DIY-er, Exeter

175 guides
Choosing the right bit for your drill is no easy task. From high-speed steel to carbide tips and straight shanks through to SDS Max, there are endless options out there. With that in mind, here are our tips for selecting the best metal, masonry or wood drill bits for your job. Let's get drilling!

Important features

  • Drilling material
  • Shank
  • Drill bit material
  • Point and flute design

Price

from £1.00 to £2,060.00

An overview of drill bits

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.

How to choose your drill bits

Drill bit type

 

Shank type

 

Drill bit material

 

Quality

 

Special features

Drilling material

Feature

Quality

Masonry drill bit

Straight shank, SDS+, SDS Max

Tungsten carbide

From
***
to
****
 (according to percentage)

2 cutting edges

**

Concrete - Reinforced concrete - Breezeblock - Stone

3 cutting edges

****

4 cutting edges

******

Carbide

******

Carbide tip

******

Metal drill bit

Straight and hex shank

HSS

**

Rolled steel (standard use) or ground steel (frequent use)

Non-ferrous metals

HSS-R

**

HSS-G

***

Titanium

****

Ground drill bit

 

Tungsten carbide

****

Cobalt

*****

Ground drill bit

Ferrous and non-ferrous metals - Stainless steel, etc.

Solid carbide

******

Ground drill bit

All steel

Wood drill bit

Straight and hex shank

Steel

****

Flat drill bit

Joinery wood

Three-pointed bit

Auger bit

Timber

Tile drill bit

Straight shank

Tungsten carbide

***

Step bit

Tile - Ceramic - Roof tile

Glass drill bit

Diamond

****

Step bit

Glass

Choosing a metal 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:

  • High-speed steel (HSS): an alloy steel (an alloy consisting of a metallic element combined with a chemical element to give the steel a certain feature);
  • Hard metal or carbide: a sintered compound created through a manufacturing process whereby powdered forms of carbide tungsten are heat-treated with binder metals, such as titanium or cobalt, to make a solid.

The main types 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 (HSS)

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

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

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 of a bit.

Tungsten carbide


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.

Different types of HSS metal drill bits

HSS metal drill bits feature a helical, or twisted, shape and come in various materials providing different degrees of hardness and durability.

High-speed steel ground metal drill bits


HSS-G
 bits 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.

High-speed steel rolled metal drill bits


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.

Tips for choosing metal drill bits


  1. Point angle varies from drill to drill (90°, 120°, 135°, 140°, 145°) and should be tailored to the metal you plan on drilling. The harder the metal, the larger the point angle (and therefore the flatter the point). This factor also depends on the drill bit material.
  2. Rolled metal bits are generally considered entry-level bits. Ground drill bits are recommended as a minimum level of quality for regular use.
  3. HSS-Co 5% bits (HSS bits with additional cobalt) offer good value for money. When used with a cutting fluid at a low speed, these bits can tackle numerous metal drilling tasks.
  4. Solid carbide bits are top-of-the-range bits that allow you to bore deep holes in metals.
  5. Nevertheless, most metals can be drilled with the use of any well-sharpened bit of average quality, as long as you use cutting fluid and the correct drilling speed

Comparing metal drill bits

 

Metal drill bit Ø 10mm

Minimum resistance

Durability

Metal type

Price

HSS

900 N/mm²

**

Non-ferrous metals

≤ £13

 

HSS-R

900 N/mm²

**

Non-ferrous metals, grey cast iron

HSS-G

900 N/mm²

***

Alloy and non-alloy steel, non-ferrous metals, grey cast iron and malleable iron, sintered iron

Tungsten carbide

From 1000 to 1100 N/mm²

****

Soft metals, non-ferrous metals

≤ £17

Titanium (titanium nitride)

Approx. 1000 N/mm²

****

Alloy and non-alloy steel, malleable iron, sintered iron, non-ferrous metals

≤ £26

Cobalt (0.5 or 0.8%)

From 1000 to 1200 N/mm²

*****

Hard and treated steels; stainless steel, chrome nickel, cast iron and bronze

≤ £260

Solid carbide

From 1200 to 1500 N/mm²

******

All alloy and non-alloy steel, ferrous and non-ferrous metals

≤ £750

Tips for choosing a masonry drill bit

Selecting a masonry drill 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.

Masonry drill bit shank types

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:

  • Straight shank: used for hammer drills and drills with keyed or keyless chucks;
  • Slotted Drive System (SDS): a drill bit with a grooved shank that clicks into the chuck. This shank is found on most hammer drills and various brands of standard drills. There are two types of SDS shank:
    • SDS+ shanks are used on hammer drills weighing between 2 and 4 kg, with 1200W of power or less;
    • SDS Max shanks are used for more intensive work (professional ranges) and hammer drills weighing more than 4 kg, with at least 1200W of power.

Most concrete drill bits feature SDS+ shanks. SDS Max shanks are used for heavy-duty jobs and with other hammer drill accessories such as flat chisels, moil points, and so on. 

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.

Features of masonry drill bits

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:

  • L-type double flute: standard model;
  • U-type double flute: for better dust removal;
  • Four-flute model for better stability;
  • Turbo design for optimum dust removal.

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.

Different types of wood bit

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.

  • Flat wood bits are used for drilling large diameters (generally 13 mm+). That being said, you can also find 6 mm flat wood bits.
  • Twist bits are mainly supplied with diameters ranging up to 17 mm, although these can also go beyond 20 mm. 
  • Auger bits, specially designed for removing shavings while drilling wide holes (in carpentry).Three-point bits are the most common and precise variety of wood bit; these are used in carpentry for drilling small holes. These bits have three points: one central point and two points on the sides that draw out the hole before drilling.


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.

More drilling accessories

In addition to the many variations of metal, concrete and wood drill bits, a range of drilling accessories may also prove useful.

  • Step bits (or unibits) are cone-shaped bits equipped with a range of different diameters to drill various hole sizes;
  • Stub drill bits feature a short length for drilling into very hard metals and drilling out spot welds;
  • The Forstner drill bit is mainly used in cabinet-making for drilling large holes (for hinges, for example), and is also known as a hinge bit;
  • Extendable drill bits are wood bits that are used to drill several hole sizes (usually ranging from 13 to 45 mm) using just one bit. They are mainly used for drilling into plywood and thin composite panels such as chipboard;
  • Countersink drill bits are used to drill a countersink (for drilling pilot holes or entering a screw head);
  • Installer drill bits are very long bits, designed to drill holes for pulling through wires;
  • Hole saws are not necessarily categorised as bits but they can be fitted onto a drill to create different sized holes in a range of materials;
  • Concrete hole saws, or diamond core drills, are a type of heavy-duty hole saw used to drill into concrete; 
  • Extension rods are handy for wood drilling and allowing you to drill deep holes (as long as the drill has a larger diameter than that of the extension bar).

More information

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Guide written by:

Sebastian, self-taught DIY-er, Exeter 175 guides écrits

Sebastian, self-taught DIY-er, Exeter

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!

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