A wire crimper is used to tighten the crimps you use to make permanent electrical connections.
If you're doing electrical work, you shouldn't be without a good crimper. Sure, you can try to get it done with pliers or wire cutters, but that's kind of like fishing with a baseball bat in a swimming pool wearing a hoop skirt. That's right, it's ignorant.

There are two common types of crimpers. The most used is a universal crimping tool that is also a wire stripper.

These work well enough, but if you are serious about your wiring, you might choose a dedicated crimping tool. It is a lot easier on your hands and really squeezes the crimp into a binding shape. With either tool, you place the jaws around a crimp (which already has the wires that need joining on the inside) and squeeze. It's a good idea to give the wires a test pull before you call it done. It might be a pain in the butt if you pull one out, but better that it happen now. If a wire pops out of its crimp down the road, you could witness a meltdown, and that ain't pretty.

Check out a picture of some wire crimpers.

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