How To Tighten The Bolts And Nuts?

Threaded connections using bolts and nuts are the most common in fastener applications. In order to ensure the strength of the connection, self-locking nuts or additional mechanical locking are used to prevent loosening. The installation of threaded fasteners is also very simple, as long as there is enough torque to achieve the preload at the interface, but many people are still not sure whether to tighten through the nut or bolt head. In the process, they may have some doubts, for example, should torque be applied to the bolt head or the nut when tightening? If torque is applied to the bolt head or nut, is the result the same? As a professional fastener manufacturer, Xinchi Fastener Company has many years of experience in the fastener field, we are happy to answer relevant questions.

In some applications you can apply torque to the bolt head or nut and keep it tight; In the following applications, it is possible to apply torque to only one of the components.

1. Interference fit: Torque should be applied to the nut in the hole of the interference fit for installation.
2. When the bolt head and nut have different shapes and diameters, torque can be applied to only one of them. When the bolt head is of a different shape from the nut (such as a hexagon bolt with a square nut) or has a significantly different diameter, it is best to apply torque on the side with the smaller bearing surface. For example, if the bolt head is smaller than the nut, torque should be applied to the bolt head. It can be simply understood as applying torque from a small place and bearing force from a large place.
3. Different materials: When two different materials need to be clamped together, it is best to apply tightening force to the material with a low coefficient of friction, that is, torque tightening on the side that is likely to produce the least friction.
4. Long bolt application. Torsional winding is a very easy problem to occur when torque is applied to the head of a very long bolt, so applying torque to the nut in this case will help avoid this problem. There is an application where the nut is a nut with a flange but the bolt head does not, meaning that the friction radius on one side of the nut is greater than on the side of the bolt head.

If the tightening torque is determined when the nut is to be tightened, then an overload problem may occur if the bolt head is tightened using that torque. Typically, nearly half of the torque is needed to overcome friction under the tightening surface, so a smaller radius of friction will cause more torque to enter the threaded joint and thus cause over-tightening problems. And vice versa. Assuming that the torque is determined by the tightening of the bolt head if the nut is tightened, that is to say, the torque is applied to the side with a greater radius of friction, which results in insufficient preload at the input thread connection and may cause loose problems.

Anji Xinchi Fastening Piece Co., Ltd 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.