How to use a torque wrench
What is it?
A torque wrench is like a normal wrench in that it lets you tighten or loosen nuts and bolts on your car. But it can be set to tell you when you've tightened a nut to a particular amount, e.g. 9 foot lbs, so you don't tighten it too much and damage the threads on the nut.
Replacing a stripped nut in certain parts of your car can be a real nightmare, so having a torque wrench can save you lots of time and hair- pulling by helping you do a job right.
How to use it
On the end of the torque wrench is a dial or other way of setting where you want to stop tightening, and usually a gauge to show you where it's set. Twist the dial and watch the guage, it will gradually change to show a different pressure level. The wrench my dad has both metric and imperial measurements, make sure you're following the right one for what your guide says.
Look up in a manual how tight something should be, for instance the flywheel gland nut should be tightened to 220 Ft. Lbs. (30 Kg if you have a metric-only wrench.) Set the right level on the guage and start tightening up the nut. Don't try and do it all in one go, a gradual tightening is easier to control. When you hit the level you have set, the torque wrench will 'break' - make a cracking noise and you can feel something inside the wrench giving way for a moment. Stop tightening now.
With many wrenches, you can keep tightening if you lean on the wrench, but this just means you are turning the nut further than you are supposed to and about to damage something.
If you are not sure if it is right, double check the setting on the torque wrench and try tightening the nut a little more. If the wrench 'breaks' again, you have tightened the nut enough.