If you've ever loosened lug nuts on car to take the wheels off or tightened them after putting the wheels on, you've probably used a torque wrench. Well, let me rephrase; if you've ever put the lug nuts back on an automobile, hopefully you used a torque wrench.
A torque wrench is a wrench designed to let you tighten nuts or bolts without over-tightening them, which can be prevented in a variety of ways.
Lets return to the lug nuts. If the lug nuts on your car need to be tightened to 75 foot pounds you will need to make sure you have a means of knowing when you've reached 75 foot pounds. Are you just going to use a regular wrench and guess?
That's why I said above that "hopefully" you used a torque wrench hydraulic torque wrenches. A typical torque wrench can have a gauge about it that teaches you just how much force you're applying. As you tighten the nuts the needle will indicate the quantity of force getting used that will permit you to apply precisely the right amount.
Most wrenches of this sort are fairly long allowing sufficient leverage to generate enough force. If you're tightening your lug nuts with a 16" wrench you're going to have an easier time than in the event that you try it with a 10" wrench, for example.
Although some forms of these wrenches just have a gauge to tell you just how much force you're applying, others now have mechanisms that prevent you from applying a lot of force. As an example, some wrenches have a clutch that disengages when the correct quantity of force is applied so that you cannot tighten the bolt any further.
Now, what if you're dealing with bolts that are much bigger compared to the lug nuts that hold your wheels on? What if you want to tighten something to 10,000 feet pounds rather than 100? In these cases there is another kind of wrench, a hydraulic torque wrench, that uses hydraulic power to apply the required force to the bolts. Hydraulic torque wrenches have existed considering that the mid-60's but recent improvements within their design have made them smaller, lighter, and and easier able to fit into tight spaces. This type is known as much better than pneumatic wrenches because they're quieter, lighter, and more accurate.