Products - Wrenches Index - Hex Allen Key Short Pattern

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Some features of hex keys are:
 The tool is simple, small and light.
 The contact surfaces of the screw or bolt are protected from external damage.
 There are six contact surfaces between bolt and driver.
 The tool can be used with a headless screw.
 The screw can be inserted into its hole using the key.
 Torque is constrained by the length and thickness of the key.
 Very small bolt heads can be accommodated.
 The tool can be manufactured very cheaply, so one is often included with products requiring end-user assembly.
 Either end of the tool can be used to take advantage of reach or torque.
 The tool is L-shaped

A hex key, Allen wrench, Allen key or hex-head wrench is a tool used to drive hex screws and bolts, which have a hexagonal socket in the head.

UK Specification BS:2470
International Specifications: ANSI B18.3.2M; ISO2936; DIN911. Dimensions are measured across flats (AF)
Hexagonal screws are commonly used to hold control knobs onto shafts.
Allen keys, especially in the smaller sizes, are precision tools. Make sure that you have good quality Allen keys, I bought a cheap set and found that the small sizes were out of tolerance and these can easily damage the hex screws.
With the smaller sizes, it is easy to strip the head if you are not careful. Clean out the hex hole and make sure that the key is correctly seated before applying pressure. A quick squirt of WD40 oil will help release the thread.

Allen Key (Also known as Hex Key, Hexagon Key, Socket Key, LN Key), sizes and its dimensions can be very handy while designing and selecting fasteners for your application. These dimensions of Allen keys can be used to check the accessibility of your bolts were space is limited. For example for an M8 socket head cap screw we need at least 32 8(head size) = 40mm clearance above the screw for easy accessibility. Refer the following table for metric Allen key sizes and dimensions for corresponding socket head cap screw based on ISO 4762/DIN 912 standards.

Screw Size Allen Key Size, s A B
M3 2.5 56 18
M4 3 63 20
M5 4 70 25
M6 5 80 28
M8 6 90 32
M10 8 100 36
M12 10 112 40
M14 12 125 45
M16 14 140 56
M18 14 140 56
M20 17 160 63
M22 17 160 63
M24 19 180 70