In industrial assembly screw fastening, the torque stability of a torque screwdriver directly determines the fastening quality. Torque instability can lead to inconsistent fastening effects, causing component loosening and even structural safety issues. This article analyzes the causes from multiple dimensions and provides solutions.

I. Insufficient Tool Accuracy: Inherent Design or Aging Leading to Torque Deviation

(1) Causes

• Clutch-type Torque Screwdriver Defects: Relying on internal springs to drive the clutch, these have inherently large torque dispersion. In high-precision scenarios (such as electronic component fastening), they are prone to alternating between meeting specifications and exceeding tolerances.

• Spring Aging and Degradation: After long-term use, spring elasticity decreases, causing the clutch trigger torque to drop and degrade unevenly, exacerbating torque fluctuations.

• Abnormal Component Positioning: Spring installation offset or clutch wear causing increased engagement clearance leads to unstable torque transmission, resulting in "stuttering" jumps.

(2) Solutions

• Model Selection: For high-precision applications (such as automotive electronics or medical device assembly), replace with servo-type torque screwdrivers with smaller dispersion, such as Danikor sensor-type electric screwdrivers, which can achieve accuracy of 6Σ±5%.

• Regular Maintenance: According to usage frequency, replace internal springs of clutch-type torque screwdrivers, clean clutch contact surfaces to eliminate the impact of wear debris.

II. Improper Parameter Settings: Mismatched Parameters and Scenarios Leading to Torque Loss of Control

(1) Causes

• Speed and Connection Method Mismatch: In hard connection scenarios (metal part fastening), excessive final tightening speed causes motor inertia to induce torque overshoot, resulting in torque fluctuations in the same batch of fastening.

• Missing Segmented Parameters: Complex scenarios (such as plastic part fastening) without setting "pre-tightening - transition - final tightening" segmented parameters cause high-torque rapid fastening leading to thread deformation and abnormal torque feedback.

• Monitoring Function Not Enabled: Without angle monitoring, when screws are slightly stripped, relying only on torque feedback cannot identify engagement abnormalities, causing torque to fluctuate high and low.

(2) Solutions

• Scenario-based Parameter Adjustment: In hard connection scenarios, reduce final tightening speed to prevent overshoot; in complex scenarios, set segmented parameters - use low torque and high speed for pre-tightening positioning, and low speed for final tightening.

• Enable Dual Monitoring: In all scenarios, combine "torque-angle dual monitoring", immediately stop fastening when angle is abnormal to prevent loss of control caused by parameter mismatch.

III. Mechanical Component Wear: Long-term Use Leading to Torque Transmission Deviation

(1) Causes

• Gear Set Wear: Long-term high-frequency use causes gear tooth surface cracking and scratching, increasing power transmission clearance, causing torque "idle running", and even "intermittent torque loss".

• Bit Connection Component Wear: Long-term insertion and removal of the connection shaft causes wear, leading to bit tilting during fastening, torque force offset, and torque fluctuations at the same workstation.

• Sensor Aging: Servo-type torque screwdriver sensors affected by vibration and temperature experience accuracy drift, unable to detect small torque deviations, resulting in unstable output.

(2) Solutions

• Regular Calibration: Periodically use torque calibrators for testing, adjust parameters or replace worn parts when deviation exceeds reasonable range.

• Targeted Replacement: When gear sets are worn, replace the entire kit, replace chucks or connection shafts.

• Daily Protection: After use, clean bit connection parts, store in dry environment to prevent sensor moisture.

IV. External Environmental Impact: Operational and Material Factors Causing Torque Interference

(1) Causes

• Operational Technique Deviation: When manually held, inconsistent pressing angles (large tilt angle) lead to poor coaxiality between bit and screw, decomposing torque into axial and radial forces, reducing actual effective torque and causing fluctuations; excessive pressing force increases motor load causing abnormal torque.

• Material Adaptation Issues: Insufficient precision in screw and threaded hole fit (thread pitch deviation, rough tapping) causes engagement resistance fluctuations; oil or burrs on screw surface cause uneven friction, all leading to torque feedback fluctuations.

(2) Solutions

• Standardized Operation: Train operators to maintain coaxiality between bit and screw during fastening (control tilt angle within small range), apply even pressure, and use pressure feedback function for monitoring.

• Material Preprocessing: Before fastening, check screw and threaded hole specification matching, remove oil and burrs, polish rough threaded holes to reduce resistance fluctuations.

• Optimize Workstation: For mass production, use fixture jigs to fix workpieces to avoid position deviation caused by manual holding.

Conclusion

Torque instability in torque screwdrivers requires multi-dimensional investigation. Through proper model selection, scientific parameter setting, and regular maintenance, torque fluctuation problems can be solved, tool life extended, industrial assembly fastening ensured, and product quality risks avoided.