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Hex Keys
A hex key is an L-shaped wrench for hexagon socket screws: the long arm spins the screw, the short arm gives torque in tight quarters. A ball end lets you enter at an angle, but the final tightening always goes through the straight end. Metric and SAE sizes are listed here in standard and long patterns, with T-handle and Torx® versions and complete sets.
Elta Hex Key Wrench Standard Size 1.5 mm
Elta · Hex Keys
Elta Hex Key Wrench Standard Size 10 mm
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Elta Hex Key Wrench Standard Size 12 mm
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Elta Hex Key Wrench Standard Size 2.5 mm
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Elta Hex Key Wrench Standard Size 2 mm
Elta · Hex Keys
Elta Hex Key Wrench Standard Size 3.5 mm
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Elta Hex Key Wrench Standard Size 3 mm
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Elta Hex Key Wrench Standard Size 4 mm
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Elta Hex Key Wrench Standard Size 5 mm
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Elta Hex Key Wrench Standard Size 6 mm
Elta · Hex Keys
Elta Hex Key Wrench Standard Size 7 mm
Elta · Hex Keys
Elta Hex Key Wrench Standard Size 8 mm
Elta · Hex Keys
Elta Hex Key Wrench Standard Size 9 mm
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Elta Hex Key Wrench Set (mm) 10 Pcs
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Elta Hex Key Wrench Set (mm) 7 Pcs
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Elta Hex Key Wrench Set (mm) 9 Pcs
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Elta Hex Key Wrench Folding Set (6 Pcs, mm)
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Elta Hex Key Wrench T-Handle 10 mm
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Elta Hex Key Wrench T-Handle 2.5 mm
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Elta Hex Key Wrench T-Handle 3 mm
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Elta Hex Key Wrench T-Handle 4 mm
Elta · Hex Keys
Elta Hex Key Wrench T-Handle 5 mm
Elta · Hex Keys
Elta Hex Key Wrench T-Handle 6 mm
Elta · Hex Keys
Elta Hex Key Wrench T-Handle 7 mm
Elta · Hex Keys
Which key fits which screw
A hex key's size is the across-flats dimension of the socket in the screw head, not the thread diameter. For metric socket head cap screws (DIN 912 / ISO 4762) the pairings are in the table below, and the commonest mistake in practice is forcing a key one size down and chewing the socket out.
When a key will not seat, the cause is usually dirt or paint in the socket rather than the size. Forcing it before the socket is cleaned ruins both.
| Screw (DIN 912) | Hex key |
|---|---|
| M3 | 2.5 mm |
| M4 | 3 mm |
| M5 | 4 mm |
| M6 | 5 mm |
| M8 | 6 mm |
| M10 | 8 mm |
| M12 | 10 mm |
| M14 | 12 mm |
| M16 | 14 mm |
| M20 | 17 mm |
Common pairings for socket head cap screws; other head types can differ.
Straight, ball end and T-handle
A straight key seats fully and carries full torque. A ball end lets the key enter at up to about 25 degrees off axis -- useful for reaching a screw, not for finishing it. Full torque through a ball end rounds both the tip and the socket.
A T-handle gathers the grip of both arms into one hand and is fast in repeat assembly. 1000V insulated T-handle hex keys are also listed here, insulated for work in live switchgear.
Torx® and material
Torx® keys share the body shapes but carry a star profile instead of a hexagon. The wider contact carries more torque at the same size with less risk of chewing the socket out. Sizes from T6 to T50 are listed here, including T-handle versions.
Hex keys here are made from chrome vanadium and nickel plated, to TS ISO 2936, which fixes the tolerance on the across-flats size -- so play in a non-standard key really is a larger gap.
Frequently Asked Questions
Which hex key fits an M8 screw?
A socket head cap screw (DIN 912) in M8 takes a 6 mm key. M6 takes 5 mm, M10 takes 8 mm, M12 takes 10 mm; other head types can differ.
Can I torque a screw down with a ball end?
No. The ball end is for entering at an angle; its contact area is small and full torque rounds both the tip and the socket. Finish with a straight end.
The key spins in the socket -- what now?
First make sure the socket is clean of dirt and paint; that is most cases. If the size is right and the socket is chewed out, the next step is an extractor bit or drilling the head off.
Standard or long pattern?
The long pattern reaches screws in counterbores and deep holes; the standard pattern works in confined space and is stiffer. Both are listed in metric and SAE.
How does Torx® differ from hex?
The Torx® star profile has more contact area than a hexagon, so it carries more torque at the same size with less risk of chewing out. The two are not interchangeable.
What is a T-handle hex key for?
One-handed grip and speed in repeat assembly, and it makes it easier to hold the screw straight. The 1000V insulated versions are for live switchgear.