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• ISO 2936 - Short / Long Arm

ISO 2936 Hex Keys

ISO 2936 SpecificationsMetric Fastener Data

ISO 2936 Hex Keys are "L" shaped keys that are used to tighten and loosen internally wrenched fasteners like socket set screws, socket head cap screws and socket shoulder bolts. They are available in short (standard) and long arm versions. The length of the short leg (bottom of the "L") is the same for short and long arm keys of the same size—only the long leg differs. The length of both legs increases as the key size increases. Long arm hex keys are used to drive screws in deep recesses and, when the long leg is used as the lever, higher torque values can be achieved. A single hex key will often fit several different screw sizes—a 3 mm hex key, for example, is used with M4 socket head cap screws; M5 button, flat and low head socket cap screws; and M6 socket set screws and socket shoulder bolts. All keys are plain finish (not plated). Also known as hex socket keys, hexagon socket screw keys, hex wrenches and Allen keys, sizes 0.7 through 8 mm have a Rockwell hardness of 52 HRC, 9 through 14 mm are 48 HRC and 15 through 36 mm are 45 HRC. Key size is specified as the width across parallel sides (flats). Since hex keys aren't threaded, their size is correctly designated in mm (millimeters), such as 4 mm, but it is common to see "mm" omitted and their size preceded by the letter "M" (which denotes metric screw thread), as in M4. To avoid confusion, we reluctantly follow that practice.