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Allen wrenches are used to drive screws and bolts with hexagonal sockets. They are commonly used in furniture assembly, bicycle maintenance, machinery, and various household applications.

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While it might seem logical to assume that a screw would take the same size hex key as the screw size (that a M4 button head would take a M4 hex key for example), but this isn’t the case. Hex keys are defined by the dimension of their cross-section, which is roughly half of the nominal screw size. A M4 Button Socket cap screw would take a M2 Hex key (as the hex dimension is actually 2.0mm across).. The socket recess is a very different size and is different from screw type to screw type as shown here.

To use an Allen wrench, insert the short or long end into the hexagonal socket of the screw or bolt. Turn the wrench to tighten or loosen the fastener. The L-shape provides leverage, making it easier to apply torque.

Yes, Allen wrench and hex key are two terms for the same tool. They both refer to a six-sided, L-shaped tool used to drive screws and bolts with a hexagonal socket.

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Yes, you can use hex insert driver bits with a drill. These bits fit into the chuck of the drill and have a hexagonal end that matches the size of the Allen wrench you need.

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Allen wrenches come in a variety of sizes. In the US, common sizes range from 0.028" to 1". Metric sizes typically range from M0.9 to M19. These sizes correspond to the width across the flats of the hex key.

If you don't have an Allen wrench, you can use a hex bit with a screwdriver or drill. In some cases, small adjustable wrenches or pliers might work, but they may damage the fastener.