Standard operating procedure for torque wrench
Release Time：
2025-05-30
Torque Wrench Usage Standards
I. Pre-use Preparations
Calibration and Inspection
Check if the scale is clear and the handle is undamaged. Send for repair if any abnormalities are found.
Perform 3-5 unloaded operations to confirm the flexibility of the mechanism.
Tool Selection Matching
Select the wrench type (preset, digital display, dial type) and torque range according to the scenario, for example:
Light bolts (such as plastic parts): 5-20Nm.
Engine cylinder head bolts: ≥100Nm plunger type wrench.
The socket must precisely match the bolt head, with a tolerance ≤0.1mm.
II. Torque Setting and Operation
Torque Value Adjustment
Preset type: Unlock the rear knob → Rotate the main/secondary scale to align with the target value → Lock the knob.
Example: To set 192Nm, the main scale needs to align with 190, and the secondary scale is adjusted to 2.
Digital display type: Enter the target value through the control instrument. The calibration error must be ≤±1.5%.
Force Application Standards
Hold the middle of the handle, and the angle between the direction of force and the wrench axis must be ≤10°.
Apply force evenly. Stop immediately when you hear a "click" or the digital display alarms.
Long bolts need to be tightened in steps: Pre-tighten to 30% torque → Gradually increase to the set value.
III. Special Scenario Operation Points
High altitude/confined spaces:
Use a socket with a universal joint to prevent skewed force application.
Digital display wrenches need a fixed reaction arm to prevent the fulcrum from sliding.
Hydraulic Wrench:
Check the oil pipe connections before starting, and idle for 3 times to exhaust air.
When removing nuts, switch the direction conversion knob to reverse gear.
IV. Post-use Maintenance
Cleaning and Storage
Wipe off oil stains and apply rust preventive oil. The storage environment humidity should be ≤60%.
Reset the preset wrench to zero and lock it to avoid long-term pressure on the spring.
Periodic Calibration
Calibration with a torque tester is required every 5000 operations or every six months.
Do not use digital display wrenches when the battery is low to prevent data drift.
Key Prohibitions:
Do not use beyond the rated range (e.g., using a 20Nm wrench to tighten a 100Nm bolt).
Do not use it as an ordinary wrench to remove screws or strike workpieces.
If the hydraulic wrench oil temperature exceeds 60℃, stop and cool.
Through standardized operation, the service life of a preset wrench can reach 20,000 cycles, and the accuracy of a digital display wrench can be maintained within ±1%.
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Email：cs@fomadon.com
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