Overview of drill bit types

Which drill bit is suitable for which material?

Drill bits can be used to drill different holes in a variety of materials.

The best-known drill bit types are

Metal drill bits
Wood drill bits
Stone/concrete drill bits

Metal drill bits

There are various metal drill bits due to the wide range of possible applications. Below is a selection of drill bit types that are frequently used in metalworking.

Twist drills

Twist drills are among the most frequently used tools for drilling. The decisive factor for twist drills is the helix angle (Fig. 2). This is the angle between the flute and the drill axis. The correct twist angle of the drill bit is the basis for being able to process the correct material, because the harder the material, the smaller the twist angle should be. There are three standardised drill bit types for twist drills:

Type W
Type N
Type H

If the workpiece dissipates heat poorly during drilling, a smaller point angle should be selected.

To the twist drills

Three twist drills of different sizes lie on a grey surface. The drill bits are copper-coloured and have a spiral-shaped groove.

Close-up of a drill bit on wood with text labelling. The drill has a red, dashed axis, a flute and angles are marked.

	Type W	Type N	Type H
Suitable for	Soft materials (copper, aluminium, plastics)	Normal hard materials (steel, cast steel up to 400-700 N/mm²)	Hard, tough, brittle materials (hard plastics, brass, steel over 1200 N/mm²)
Twist angle	35° to 40°	16° to 30°	10° to 13°
Tip angle	130°	118°, 135°	80°, 118°, 135°

Resharpening twist drills

Steel drill bits can be resharpened on a bench grinder or belt grinder. In addition to the correct point angle, which can be determined and checked using a protractor (Fig. 1) or a grinding gauge (Fig. 2), it is also important to ensure a proper relief grind. Observe the following tips to avoid common sanding errors:

If necessary, machine the grinding disc with a diamond dresser (image 3) so that it is flat, clean and sharp enough to sharpen the drill bit in the best possible way.
The surface behind the cutting edge must be ground downwards (Fig. 4) so that the cutting edge itself is the highest point (relief grinding [Fig. 5]). Otherwise the drill presses and does not cut.
Both cutting edges must be the same length. If this is not the case, the tip will be off-centre and the drill hole will be larger. In addition, the drill bit wears out more quickly as the longer cutting edge is more engaged.
Unequal cutting angles cause greater wear. While only the cutting edge with the flatter angle is engaged, the tool life and drilling performance are halved.

Please note that only uncoated drill bits should be resharpened.

A metal protractor is used to measure the angle of a drill bit. The protractor shows approx. 118 degrees. Two hands hold the tool and knife.

Close-up of a twist drill tip being measured with a metal angle gauge. The gauge shows a scale from 0 to 2.

A hand holds a piece of metal against a rotating grinding disc. Sparks fly during grinding, removing metal.

A man grinds a drill bit on a grinding disc, causing sparks to fly. The machine is blue and the drill is held by one hand.

Close-up of a drill, the back cut and cutting edge labelled, against a neutral background.

Core drill

Core drills can be used to drill precisely fitting holes without pre-drilling. The special feature of this type of drill is that the drill core remains inside the drill bit and only a narrow ring is cut. This means that there is less wear on the drilling tool and faster advance is possible. The drill core that remains in place is pushed out by an ejector pin. Core drills can be used with conventional drilling machines and magnetic drilling machines.

To the core drills

Three core drills of different sizes stand on a grey metal surface with red accents. The drill bits have spiral-shaped cutting edges.

Step drills

Step drills are suitable for burr and chatter mark-free drilling and reaming of sheet metal, pipes and profiles. Different diameters can be achieved thanks to the drill's different sized steps. Step drills are mainly used in metal construction and in the automotive sector and can be used in hand or pillar drills. Pre-drilling is also recommended when using step drills.

To the step drills

Two silver step drills lie on a grey surface with red details. The drills have conical shapes with printed size information.

Centre drill

This type of drill is used to create a centring point on workpieces. This centring hole allows, for example, a centre point to be used to support the workpiece via the tailstock of a lathe. A centre drill can also be used for pre-drilling. Due to the small dimensioned centre point of the drill, low radial forces and reaction forces occur through the chip when drilling into a workpiece. This prevents the drill from "running", which significantly improves the positioning accuracy of the hole to be drilled. Centre drills are particularly short and have a stepped profile with an additional centre point at the very front. The diameter of this tip is also the nominal diameter of the centre drill.

To the centre drills

Three centring drills in grey, gold and silver on a workbench. Each drill is labelled in the centre with "Paulimot HSS" and the size in mm.

Comparison of drill bit types for metal

	Twist drill	Core drill	Step drill	Centre drill
Field of application	➤ are particularly suitable for machining metal due to their geometry	➤ are particularly suitable for through holes with larger diameters	➤ a re suitable for burr and chatter mark-free drilling and reaming of sheet metal, pipes and profiles	➤ are suitable for producing centre holes on workpieces

Coatings

Special coatings allow metal drills to be used for machining materials of different hardnesses.

Possible coatings:

TiN-coated (titanium, nitrogen)
TiAlN-coated (titanium, aluminium, nitrogen)
AlTiN-coated (aluminium, titanium, nitrogen)
AlTiSiN-coated (aluminium, titanium, silicon, nitrogen)

You can find a brief overview of the different coatings for metal drills in our information sheet:

Comparison of coatings (PDF)

Four drills of different types and colours, from left to right: silver, gold, blue and silver.

	TiN	TiAIN	AITiN	AITiSiN
Components of the coating	Titanium, nitrogen	Titanium, aluminium, nitrogen	Aluminium, titanium, nitrogen	Aluminium, titanium, silicon, nitrogen
Suitable for soft materials (aluminium, plastics, non-ferrous metals, brass, copper, bronze)	+	+	+
Suitable for hard materials (stainless steel, steel, titanium alloys)	+	++	++	+
Suitable for very hard materials (e.g. hardened, alloyed steel grades)		+	+	++
Coating colour	gold	Black, anthracite	Copper colours	Copper colours

Tips & tricks when working with metal drills

Make sure you cool your tools to increase their service life.
Regrind your uncoated drill bits if they have become slightly blunt.
If necessary, machine the cross cutting edge of the drill bit (Fig. 2).
Always clamp the workpiece in a vice (e.g. drilling machine vice) so that it is optimally secured.
Observe the correct speed for each type of drill bit in order to increase the service life of the drill bit. The speed specifications are usually given in a table on the drill.
Wear appropriate protective equipment (e.g. safety goggles, hairnet) and avoid gloves, jewellery and loose clothing.

Guide: Cooling and lubricating

Metal drill drills through a workpiece fixed in a turquoise-coloured screw clamp on a workbench. A hand adjusts the screw clamp.

Close-up of a drill lying on a wooden surface. You can see the spiral of the drill bit and the cross-cutting edge at the tip. A red arrow points to the cross-cutting edge.

Wood drill bits

Compared to metal drill bits, wood drill bits have a small centre point that prevents the drill bit from running in the wood. In addition to twist drills for wood, the following types of drill bits are frequently used in woodworking:

Auger bits, Lewis shape

Forstner bits

Hole saws

Auger bits

Auger bits are particularly suitable for deep-hole drilling in softwood and European hardwood, such as beech and oak. However, they are not suitable for tropical hardwoods. The auger bit is also used for drilling through holes in beams and rafters and for making deep blind holes. Drill bits up to a diameter of 20 mm are used in hand drills or powerful cordless screwdrivers.

Auger bits are equipped with a centring tip, which enables very precise centring of the drill bit. The retractable thread on the centre point also pulls the drill bit into the wood so that less pressure needs to be exerted when drilling.

To the auger bits

Three auger bits lie on a wooden surface. They have a spiral and a threaded centre point.

Forstner bits

Forstner bits can be used to produce clean and dimensionally accurate holes thanks to their centre point. This type of drill bit is used, for example, in the production of blind holes or in furniture construction when making mounting holes for pot hinges. This type of drill bit can also be used to drill out knotholes easily and precisely.

Forstner bits are suitable for soft and medium-hard types of wood and are often used in upright or pillar drills or hand-held drills.

To the Forstner bits

Close-up of a piece of wood with two drill holes and two Forstner bits, surrounded by wood shavings.

Hole saws

Hole saws are attachments for drills that can be used to drill holes of different sizes in wood. The toothed saw blades and the centre point, which make drilling in wood easier, are typical of hole saws.

Hole saws are often used to drill holes with large diameters, e.g. for electrical sockets in wood or drywall. Due to their material, bi-metal hole saws can be used not only for soft to medium-hard materials (wood), but also for harder materials such as steel and non-ferrous metals.

To the hole saws

Tool case with red hole saws of different sizes. Some hole saws are silver-grey and have a grainy texture on the cutting edge.

Comparison of drill bit types for wood

	Twist drill	Auger bits	Forstner bits	Hole saws
Field of application	➤ Making smaller (deep) holes	➤ Making deep holes (e.g. through holes, blind holes)	➤ Making holes with a flat bottom (e.g. hinge holes)	➤ Making holes with a large diameter

Tips & Tricks for working with wood drills

If you are working with twist drills, you can also use a cordless drill - a drill is not absolutely necessary.
Make sure you use the correct speed: the smaller the hole, the higher the speed should be.
To obtain clean drill holes, pay attention to the wood grain. As a rule, you should always drill along the grain of the wood.
Ensure that the workpiece is sufficiently secured. This can be secured with a screw clamp, for example.

Forstner bit drills a hole in a tree stump, chips fly. A hand stabilises the wood. A drilling machine can be seen in the background.

Masonry drill bits

Masonry drill bits have a brazed-on carbide plate on their conical tip, as the stone is made porous by impacts during drilling. Masonry drill bits are therefore more resistant and do not chip the material, but rather shatter it.

This type of drill bit is usually used in impact drills or hammer drills to work on hard materials such as concrete, stone or tiles. Masonry drill bits can have both ground and blunt cutting edges.