Choosing hex and torx keys: types, sizes and uses

Hex and torx screws are everywhere: in furniture, taps and shower heads, bicycles, door hardware, machines and power tools. An ordinary screwdriver will not get you far there. The right key in the right size makes the difference between a screw you tighten or loosen in one go, and a head that gets stripped. In this blog you will read which types there are, which sizes you need most often and what to look for when choosing.

👷 Calling in a professional is never superfluous. If it concerns a seized bolt in an installation, a tap that will no longer close or a screw in a safety component, it is better to leave it to a professional. A professional knows how much force a component can take and has the tools to loosen stuck screws without damage.

Hex and torx: what is the difference?

• Hex (Allen): a hexagonal recess in the screw head. Hex screws are found in furniture, bicycles, sanitary ware and machines. The size is given in millimetres, for example 4 or 5 mm.
• Torx: a star-shaped recess with six rounded points. Torx transfers force better than hex, so the key is less likely to slip out of the head. Torx is common in construction screws, cars, electronics and power tools. The size is given with a T, for example T20 or T25.
• Torx with a hole (tamper-resistant): a torx head with a small pin in the middle. These screws are used where not everyone should be able to undo them, such as in public spaces and in some appliances. You need a key with a hole in the tip.

💡 Never confuse torx with hex. A hex key sometimes fits halfway into a torx head, but you damage the head on the first turn.

What types of keys are there?

L-shaped keys

The classic key. The short end gives you plenty of force for loosening and tightening, the long end lets you turn quickly. A hex key set with extra-long arms gives more reach and more leverage.

Ball-end keys

A ball end on the long side lets you work at an angle of up to about 25 degrees. Ideal for screws in awkward places, such as behind a washbasin or under a cabinet. Use the ball end only for quick turning and the straight end for tightening and loosening with force: a ball end is less strong.

Torx keys

A set of extra-long torx keys with long arms is handy for construction screws, hinges and machines. A combined set of torx and hex keys of torx and hex keys is a good basis for anyone who comes across both. For torx screws with a pin in the middle, use a set of tamper-resistant torx keys.

Single keys in large sizes

For heavy bolts in machines, racking or scaffold parts you sometimes need a large size, such as a single 10 mm ball-end hex key. A single key of good steel is then stronger than the largest key from a small set.

Bits for the drill driver

If you have a lot of screws to drive, you work faster with bits in a cordless drill driver. A bit set with hex and torx bits or an extensive 40-piece torx, hex and spline bit set covers almost everything, and with a magnetic bit holder the screw stays on the bit. You can read how the Stalco 20V battery system works in our blog on the Stalco 20V battery system.

Which sizes do you need most?

A handy rule of thumb when choosing a set:

• Hex 2.5 to 6 mm: furniture, door handles, taps, shower heads and bicycles.
• Hex 8 and 10 mm: heavier bolts in machines, racking and bicycle parts.
• Torx T10 to T30: construction screws, hinges, power tools and appliances.
• Torx T40 and larger: heavy structural screws and machines.

A set with hex sizes from 1.5 to 10 mm and torx from T10 to T50 is sufficient for most jobs at home and on site.

What to look for when choosing

• Type of steel. Keys made of S2 or chrome vanadium steel are harder and wear less quickly than keys made of soft steel. A worn or rounded tip damages the screw head.
• Fit. The key must fit tightly in the head. Play means a greater chance of stripped screws.
• Length. Long arms give more reach and leverage, short keys fit better in tight spaces.
• Colour coding. Coloured keys are easier to find and you pick the right size more quickly.
• Holder. A set in a holder keeps your keys together and in order. That way you can see at once if one is missing.

You can read more about other wrenches, such as combination wrenches, in our combination wrench guide. More about screwdrivers and bit sets can be found in our blog on screwdrivers, bit sets and screw extractors.

How to prevent stripped screws

1. Always choose exactly the right size and profile. If in doubt, try the larger size first.
2. Push the key all the way to the bottom of the screw head.
3. Clean the head first with an awl or compressed air if there is dirt or paint in it.
4. Use the short end of the key for the final tightening and the first loosening.
5. Do not tighten harder than necessary, especially in plastic, aluminium or soft wood.
6. On a drill driver, use a low torque setting and finish by hand.

If it does go wrong, you can often still remove a damaged screw with a set of screw extractors. If that does not work, or the screw is in a component you should not simply drill into, call in a professional.

Working safely

Wear work gloves with nitrile coating for grip, especially with greasy or oily bolts. Use safety goggles when working with force, drilling with a screw extractor or using compressed air to blow a head clean. Never put an extension pipe on a hex key: the key can break or shoot out of the head. If you work on electrical appliances or installations, first make them dead. Leave work on electrics to a qualified installer.

Frequently asked questions

Can I use a hex key for a torx screw?

No. Sometimes it seems to fit, but you damage the head. Always use a torx key or torx bit in the right size.

What is the advantage of a ball end?

With a ball end you can work at an angle of up to about 25 degrees. That is handy in hard-to-reach places. For a lot of force, use the straight end.

Which sizes do I need for furniture?

For most furniture and cabinets, hex 3, 4, 5 and 6 mm will do. A complete set is handy, because then you never have to search.

What do I do with a stripped hex screw?

First try carefully tapping a torx bit that is just slightly larger into the head, or use a screw extractor. If that does not work, leave it to a professional.

Read also: How to organise a workshop or garage

Read also: How to install a kitchen cabinet

Where can you find everything for this job?

At Saniso, the online store for DIYers and professionals, you will find tools, materials and personal protective equipment for your job.

• Browse our construction tools and our workwear and safety.
• Create a customer account and order easily.
• Working on a bigger project or want to hand over the job? Request a project quote.
• Book a showroom visit, at least 24 hours in advance.
• Not sure which material suits your job? Get in touch with us.

In doubt about the approach? Feel free to call in a professional.

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