Janie Travis Wrenches September 11th, 2018 - 08:06:48
If you are buying a torque wrench for your car, you should buy a 1/2 inch square drive tool, as 3/8 in drive tools only work on lower torque settings (typically below manufacturer's specifications). Adapters are available to reduce the 1/2 inch square drive to 3/8 inch square to fit the more common socket size that most people have.
Of the two types of torque wrenches, the micrometer wrench is definitely the more accurate. Typically, they are rated as being accurate to four percent of torque set. However, this accuracy can easily be lost if the wrench is not reset to zero before storage. Beam wrenches don't have this possibility of losing their accuracy, but are less accurate right out of the box. The accuracy of these beam wrenches is typically 12 percent, but can be less on higher torque settings, especially if the operator's hand is shaking from the pressure they are applying.
Most manufacturers of torque wrenches supply them with a plastic storage box to protect them. They also often come with the 1/2 inch to 3/8 inch square drive adapter; some even come with a drive extension.
Torque wrenches are precision tools and should be treated as such. Although most micrometer wrenches have a reversible ratchet head, they really should not be used as a ratchet, and especially not as a breaker bar. Most people who break their torque wrenches do so by trying to loosen an overly tight bolt with it. This overly stresses the internal mechanism, causing it to break, especially if the micrometer isn't set to a higher torque value than the pressure that is being applied.
Micrometer wrenches are pre-set to the required torque on a vernier scale. An internal spring loaded mechanism measures the torque. When the bolt is tightened to the desired torque it "clicks."