What are the model and specifications of a torque wrench?
3 Answers
The model of a torque wrench is usually determined by its torque range. A preset torque wrench with a torque range of 5-25N.m and a drive square size of 6.3×6.3mm can be used for measurement. Torque: In China, for torque ≤100, 200, 300N·m, the square edge length is 12.5mm; for torque ≤500N·m, the square edge length is 20mm; for torque ≤10N·m, the square edge length is 6.3mm; and for torque =750-2000N·m, the square edge length is 25mm. Precautions for using a torque wrench: When using a torque wrench, apply the load evenly and slowly. Do not jerk or press forcefully to avoid overload, which may cause inaccurate output torque. Stop applying the load once the preset torque is reached. Do not use a preset torque wrench to remove bolts or nuts. It is strictly prohibited to attach a sleeve to the end of the torque wrench to extend the lever arm, as this may damage the torque wrench.
Last time when helping a friend fix his car, I specifically researched torque wrenches. Generally, the wrench model depends on the drive head size, with 1/2-inch and 3/8-inch being the most commonly used in auto repair. Having these two sizes in my toolbox is basically sufficient. For specifications, pay attention to the torque range – a 20-200 N·m range is practical for regular cars, but for heavy truck repairs, you’ll need a 100-1000 N·m one. When purchasing, note the accuracy levels, which are divided into grades like ±3% and ±4%. For precision tasks like replacing engine bolts, a high-accuracy wrench is essential. Also, remember to distinguish between N·m and lb·ft units on the dial to avoid applying the wrong force and snapping the bolt. Split-type wrenches offer the flexibility of interchangeable socket heads, making them much more versatile than solid ones.
Choosing a torque wrench depends on the application. For bicycle repairs, a compact model with a 5-25 Nm range and 1/4" drive head suffices. For passenger car maintenance, I typically carry two: a 3/8" mid-range model (40-200 Nm) and a 1/2" heavy-duty version for wheel nuts. Dial indicators with click-type alerts prove most practical - digital displays tend to be fragile. Torque specifications vary significantly between materials; aluminum and cast iron components require different settings to avoid thread stripping. Regular maintenance is crucial - I have mine calibrated biannually and always reset the scale to zero before storage to prevent spring fatigue.
