There are many threaded fasteners on your car that must be tightened properly. A precise amount of tightening force, or torque, must be applied to each fastener. The tool used to let you apply precise tightening force is called a torque wrench.
To find out the manufacturer's recommended torque specifications for critical threaded fasteners on your car, look in the shop manual for your car. All car makers provide tightening specs for the critical nuts and bolts.
In the past there have been three kinds of torque wrenches available: bending beam, micrometer type and dial-indicator. My recommendation then, and now, is that the average Saturday mechanic is better off with a bending beam type. It's the cheapest. It's accurate. And it's easy to use.
Unfortunately, many do-it-yourselfers are scared off by the bending beam torque wrench, easy as it is to use. Now Sears has a new torque wrench, designed to virtually eliminate errors when tightening a fastener to a specific torque figure.
The new wrench is called Digitork. To use it, you simply turn a knob at the end of the torque wrench's handle to the desired torque setting. As you turn the knob, numbers are displayed in tow small windows in the handle. One window gives a metric readout (Newton Meters), and the other window gives an English readout (foot pounds).
Let's say you are tightening an oil pan drain plug, and the tightening specs in your shop manual say it should be tightened to 20 foot pounds (often abbreviated ft. lbs.). You would turn the adjusting knob until the number 20 shows in the "foot pounds" window, then place the appropriate size socket on the torque wrench, and tighten the plug until the wrench "clicks."
Accompanying the clicking noise will be a few degrees of free travel by the handle. That is, the handle will seem to slip slightly. This indicates that you have reached the appropriate torque value, and should not tighten further. (An instruction manual is provided with the wrench, by the way).
The Digitork wrench comes in two drive sizes, 1/2" and 1/8". The torque range of the 1/2" job is 10-150 ft. pounds (10-200 Newton Meters). The torque range of the 3/8" drive model is 5-75 ft. pounds (5-100 Newton Meters).
Sears catalog price is $54.97 for the 1/2" model, and $49.97 for the 1/8" wrench. Prices may be slightly higher in the retail stores.
On more thing. You may see torque specifications listed in either "foot pounds," or "pounds feet." Probably the more common way is "foot pounds." As far as you're concerned, both mean the same thing. But as any engineer will be quick to point out to you, the correct way is "pounds feet."
But whether the specification calls for 30 ft. pounds, or 30 pounds ft., you still set your wrench at 30.