The Torque Wrench Defined

• Many aspects of mechanics and auto repair come with factory-recommended tightness settings to be followed during repair. Failure to do so can result in mechanical failures, looseness or pressure fractures. Torque wrenches allow precision tightness to predetermined levels.
  
  Torque wrenches come in a couple of different designs, but the two most common are the socket wrench and the long-dial design. Both are crafted to plug in a regular socket, depending on the size of night being tightened, with a ¼-inch socket plug. The long-dial design has a dial and needle that shifts as pressure is applied. The preload or pre-set socket wrench style has adjustable settings that click when the right pressure is reached.
  
  

Why Use a Torque Wrench?

• When a bolt or nut is tightened it is designed to withstand a certain level of pressure. Too much tightening and the bolt will strip (i.e. the threads will shear off) or the nut edges will tear off. If working with different metals, particularly aluminum engine casings, steel bolts and nuts screwing in will easily tear the aluminum threads or crack a case edge when over-tightened. Aluminum is a much softer metal than steel. The torque wrench allows you to tighten right up to the allowable tightness without suffering the above calamities.
  
  

Tool Options

• The torque wrench tool application can be developed in a number of different ways but the design is generally the same. Variations include pneumatic torque wrenches (air pressure-driven), torque impact wrenches, hand torque screwdrivers for small precision jobs, torque wrench spanners, and more. There are also various accessories such as high-pressure sockets for extreme torque jobs and computer reading tools for improved accuracy.
  
  

Application

• When tightening with a torque wrench, make sure the bolt is already hand-tight (i.e. you can't twist it any tighter with your own fingers). Then slowly tighten with a spanner. You will feel the stopping point of normal resistance. This is the resting point of the bolt before it starts to take on pressure in the bolt cavity.
  
  If using a preload tool, set your tool to the desired tightness pressure. You will see the pressure levels engraved into the tool handle. Snap on the appropriate-sized socket to the tool and fit the entire tool system to the bolt to be tightened. When fitted, slowly but with constant pressure turn the torque wrench a quarter turn (45 degrees). This allows you to reset each time rather than trying to twist your arms all the way around in circle with constant pressure. When the tool is at the right pressure for your bolt needs, you will hear a clock or with the dial the needle will reach the pressure level. The preload click tool is better in application, since you don't have to worry about vibrations shaking the dial needle.
  
  

Proper Tool Care

• A torque wrench is designed to provide precision work and, as a result, its setting and function need to be protected to work properly. Banging, dropping the tool or chucking it into the tool back after use is a sure way to screw up the settings and function. Most torque wrench tools come with a protective case -- use it religiously. For serious precision work, you can have your tool regularly recalibrated at qualified tool repair shops.