Screwdriver bits buying guide

Screwdrivers transfer force, or torque, to the screw through the screw drive. A screw drive is a system of shaped cavities and protrusions that allow the tip of the screwdriver to slot in perfectly into the screw head. The shape and size of the screwdriver tip must match the screw head you are working on or you run the risk of damaging the screw as you attempt to tighten it.

Of course you can use a traditional screwdriver to tighten or loosen your screws. However, a power tool will always be better equipped to provide more torque meaning your screwing tasks can be completed in a matter of seconds. This will prove particularly convenient if you have a lot of screws to tighten in one go!

Screw drive types

Slotted

Slotted drives are not well suited to power driving as the screwdriver tip tends to twist out (or cam out) of the screw head as soon as the tool gains any speed. Once used for every piece of furniture and machinery, slotted screws are now only really found on old items. Sizes generally range from 3 to 6.5 mm.

Phillips

Often referred to by the code PH, the Phillips drive features a cruciform or cross recess. Though widely used, Phillips bits also tend to cam out of screw heads as the screwing speed increases. Phillips tips tend to range from 3.5 to 8 mm in size corresponding to sizes PH2 to PH5.

Pozidriv

Pozidriv or Pozi tips all have PZ marked on them and feature a similar design to a Phillips drive. However, be sure not to confuse these bits with Philips bits at the risk of stripping your screws! PZ drives are cross-shaped but also feature a 45° rib between each slot. This design allows the screwdriver to get a better grip on the screw head. There are five common sizes: PZ0 to PZ4.

Torx

Sometimes referred to as star drives, Torx drives provide very good grip. Suitable for a wide range of applications, Torx screws are increasingly being used for tasks like installing decking. The design of this drive means that there's very little chance of the tip camming out of the screw head. Sizes can range from T1 all the way up to T100, with the largest sizes reserved for the automotive industry.

Resistorx or Tamperproof Torx

These bits feature the same star-shaped design as ordinary Torx bits. However, they also feature a post in the centre to prevent a standard Torx driver being inserted. These screws provide greater security as they cannot easily be interfered with. Sizes typically range from T10 to T40.

Hex or Allen keys

Hex bits or Allen screw drives are commonly used for flatpack furniture kits. These screwdriver bits feature a smooth hexagonal shank all the way up to the tip. Hex or Allen keys are measured in across flats (or AFs) meaning the length from two parallel flat sides.

Nut setters

Nut setters are basically nut drivers designed to be used with a power tool instead of by hand. These tools are actually sockets rather than screwdriver bits and may feature six sides or twelve to fit snugly around nuts and bolts. They are often used for appliance repairs.

Triangular or Robertson

Triangular or Robertson (square) screw drives are not widely used these days. In fact, they tend to be dreaded by DIYers as it's not always easy to come across the bits to deal with them!

As seen above, screwdriver bits all vary in terms of design. However, they also vary in strength and this depends on the materials used to form the bits. Like any product, the more expensive the screwdriver bit, the higher the quality – in theory, at least!

Steel bits 

Most standard screwdriver bits are made of steel. This material offers good value for money and the bits should last a good while as long as they are used correctly.

Impact bits

If you have an impact driver, you need to use impact-rated bits as other bit types may break under the force of the tool. Impact bits are designed for heavy--duty screwing into tough materials.

Titanium tips or coating

A titanium tip or coating will make a screwdriver bit more durable than one made of steel alone. But beware: sometimes poor-quality steel is hidden beneath shiny titanium!

Diamond tips

Some screwdriver tips have been brushed with a layer of fine diamond particles. This is said to increase grip to prevent slipping on screw heads.

• Short bits are designed to deliver as much torque as possible to the screw.

Opt for high-quality screwdriver bits that match your screw head and size. Do not forget to drill pilot holes if required and always use top-quality screws. You should also remember to adjust the speed of your drill driver or electric screwdriver to protect the bit and the screw head. This will also prevent you from splitting any wooden surfaces or damaging the screw thread when screwing into metal. Finally, if you have the option, go for Torx or Pozi screws rather than traditional Phillips screws – the results say it all!

Screwdriver bit comparison

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