Reasons And Improvement Measures For Fastener Torque Exceeding Limit

In the previous article, Xinchi Fastener Company shared the Causes And Improvement Measures Of Fastener Hydrogen Embrittlement. Next, based on years of experience in the fastener industry, we will continue to introduce the causes and improvement measures of fastener torque excess.

Torque alarm usually occurs during bolt assembly where torque is controlled by the Angle method.

Failure mode and cause of fastener torque over the limit

After assembly, the final torque of the part is above or below the control limit. The reason is that the assembly torque control range of parts is unreasonable, which is manifested as too small a control range and upward or downward deviation of the control range.

Fasteners are not tightened to a preset Angle and the torque reaches the upper limit. The reason is that the friction coefficient of the parts themselves exceeds the upper limit, the friction coefficient of the parts matches exceeds the upper limit, and the interference between the parts causes the assembly torque to rise sharply.

The fastener is installed normally, torque lower limit alarm. The reason is that the friction coefficient of the part itself exceeds the lower limit or the friction coefficient of the part fit exceeds the lower limit, and the fitting torque of the part is greater than the initial torque (that is, the consumption of the screwing torque is too large), which is commonly seen in the tightening of the lock nut.

Torque system

The torque control method is to screw the bolt to a small torque first, generally 40%~60% of the tightening torque (developed after process verification), and then start from this point, screw a specified Angle control method. This method is based on a certain Angle, the bolt produces a certain axial elongation and the connector is compressed. The purpose of this is to screw the bolt to the close contact surface and to overcome some surface uneven factors, and the axial clamping force required by the rear Angle generated. After calculating the Angle, the influence of friction resistance on the axial clamping force no longer exists, so its accuracy is higher than that of the simple torque control method. The key point of the torque control method is to measure the starting point of the Angle, once the Angle is determined, you can obtain quite high tightening precision.

Xinchi Fastener Company is a trustworthy fastener company, especially in furniture nuts. And we are the designated fastener supplier to“STAPLE”. As a trusted fastener supplier,  Xinchi Fastener Company can offer a wide range of high-quality fasteners, including tee nuts, screws, bolts, rivets, washers, etc. If you want to know more about fasteners or want to wholesale fasteners, please feel free to contact us. And then our experienced and expert service team will reply to you as soon as possible.