Frankly there two reasons to buy a torque wrench – safety and longevity of parts. By allowing you to select the torque, these tools allow a degree of accuracy when it comes to tightening nuts and bolts. That may not seem important when you are repairing the broken lock on your glove box – but it is of supreme importance when it comes to the nuts that hold the wheels on, that keep the braking system intact and hold the handlebars of your Childs bike. With a regular wrench you have to tighten by eye – effectively guess at the correct torque force to tighten to. Most people overestimate to be safe – fair enough. But by using too much force over and over again, the threading on the bolt will be damaged over time, requiring replacement or even failing completely at the worst possible time.