Tightening up the various nuts and bolts on your bike is normally a bit of guesswork; if it doesn’t slip then that’s fine. However, anyone who has tried to get an over-tightened bolt undone with lashings of WD-40 will tell you it’s a tricky business if you get it wrong. Worst of all, if you over-tighten screws etc you could end up damaging the component resulting in a cost repair or even injury. Fancy carbon parts are especially prone to this.
A lot of compnents like the stem pictured above already have the correct torque setting written on them, in the case of this Ritchey stem it says 5nm (Newton Meters). Most torque wrenches have this unit on them (but not Park Tools who use the USA measure’inch pounds’) so it’s a simple case of setting the dial to the required setting and tighten the bolt.
Most torque wrenches are different so always read the instructions. Some click when the setting is reached, other like ours rock at the head to tell you the correct torque has been applied.
If you are serious about looking after your bike or are working on other people’s rides then you might want to consider investing in a torque wrench. It takes the guesswork out of cycle maintenance and may save you a few quid in the long-run.