A Quick Guide To Tightening Torques For Metric Bolts

Tighten a joint is an action less trivial than you would expect. Standard bolt tightening torque is a screw at the rated torque is not itself a promise of a proper tightening stable over time. The preload within the joint is the force that binds the two pieces together. The preload lengthens the screw and stops the unloading of the joint:

A coupling must be strengthened to:

·         Know the characteristic torque / angle of the joint

·         Joint mechanics analysis

·         Using a tightening technique with a screwdriver or lock

·   Implement a method of quality management, review the tightening quality at the end of the assembly process

Furthermore, tightening must be "certified" during essential stresses along the production lines. A calibrated tool must conduct the tightening process and parameters of the tightening must be tracked, connected to the production component and saved on a database.

You want the warranty that the tightening torque for metric bolts reaches the screw production point for such applications ( for example, vital tighteners in car assembly). The torque / angle characteristic must have enough area to prevent breakage past the yield point. Dedicated screws of a mechanical design allow the screw itself to be stretched further.

What is a goal torque?

The goal torque is typically set below the yield point. Certain stresses (e.g. critical strengthening of the cars) are done at the point of return precisely. The spring-effect of the screw is maximised by having greater preload in the junction and a decrease in the probability of decommissioning. In certain situations the couplage must be planned.

·       Do not use flat washers; the application thereof can lead to a relative motion, during tightening, to changing the nut from the washer to the joint surface. This influences the torque-tension relation by changing the friction radius. If a wider support face is appropriate due to the extreme bearing strain, the use of flanged nuts and bolts should be considered.

·     By completion of the measurements, assess the best tightening torque. The pressure gauges should be applied to the bolt shank and the real joint is tightened. A loading cell should be used under the bolt head, although it is not as exact as stress calculation because the joint properties have been altered.

The key way of managing preload is to control the torque of which the connexion is tightened. The nominal torque required to tighten the bolt to a preload can be calculated either by means of tables or a measurement using the torque-to-bolt ratio.

A quick guide to tension in torque

The torsional tension generated by the torque acting on the threads strengthens the shank directly by the elongation tension and torsional stress. The torsional stresses are neglected by the rest of the bolt tightener torques and a direct tension in threads, usually 75 per cent, is assumed. The severity of the torsional pressure for high frictional conditions will result in a failure if it is coupled with the direct stress.

The exact preload of the chosen bolt straightening process is one of the key issues in the use of bolt joints.