Fastener knowledge: common bearing head type of bolts

One end of the fastener is made into a bearing surface formed by a part of an enlarged shape. The so-called bearing surface refers to the part that supports or locates the knot, and screws are usually loaded and unloaded through the bearing surface. There are two basic types of bearing surfaces, flat bearing surface (perpendicular to the connecting rod) and tapered bearing surface (forming an angle with the connecting rod). The former serves to bear the load force acting on the connecting piece in most cases. In addition to continuing the same function of the flat bearing surface, the latter can also be used for positioning. A knot with a tapered bearing surface is usually referred to as a countersunk head type. The different applications of the head type initially depend on the function of the bearing surface and the ability of the head to transmit torque.

1. Commonly used flat bearing surface bolts and different bolt head types:

Flat head: It can replace the new design of round head and mushroom head. The head has a low diameter and a large diameter. The outer circumference of the head is connected with a high-shaped edge that indicates characteristics, so that it can drive high-intensity torque. There is a slight difference in head shape.

Round head: It is the most commonly used head type in the past.

Top column head: The diameter of the standard flat dome column head is smaller than the round head, but it is higher due to the groove depth. The smaller diameter increases the pressure acting on a small area, and can be tightly combined on the flange and Increased surface layer. They can be successfully applied to the cavity of the inner drilling due to the heading in the drilling mold set to ensure the concentration.

The dome wide-side head: Because the under-head cutting restrains and reduces the abrasion of the wire components, it is most commonly used in electrical appliances and tape recorders. It provides a relatively low head type with a more adequate bearing surface. Attractive design type.

Big round head: also known as elliptical top and wide side head, it is a low-shaped, cleverly designed large-diameter head. When the combined tolerance of the additional effect allows, it can be used to cover metal plate holes with larger diameters. It is also recommended to use a flat head instead.

Slotted head type: This is a creative anti-loosening head type. Once the combination is not easy to remove, it can be started with a standard screwdriver. This simple design can usually solve the cost problem in the combination, increase the production quantity, and create amazing economic benefits for the manufacturing process. (Guide: Five aspects should be considered in the selection of fasteners)

Hexagon socket head: A knot with a wrench head height and hexagonal head size. The hexagonal shape is completely cold-formed by the reverse hole mold, and there is an obvious depression on the top of the head.

Hexagon socket washer head: Like the standard hexagon socket head type, but at the same time there is a washer surface at the base of the head to protect the completion of the assembly to avoid damage to the wrench. Sometimes the function of things is far more important than appearance.

Hexagon head: This is a standard type of torque acting on the hexagon head. It has the feature of trimming sharp corners to close to the tolerance range. It can be recommended for general commercial use, and can also be applied to various standard patterns and various thread diameters. Because of the necessary second process, it is more expensive than the general hexagonal socket.

Socket head: The cylindrical head has a deep hexagonal socket, and the common one is CapScrew with high-strength socket head. The deeper bearing hole makes the high turning moment act on the knot.

Twelve o'clock: Twelve outer points are placed on the high cylindrical head shape, and the washer surface bears the load applied to the knot. Because of the convenience of design to provide a high degree of torque, it is often used for high-strength knots.

Plum blossom head: a medium-height hexagonal lobular head with a washer surface. Its design includes a straight surface perpendicular to the washer surface, and the torque bearing surface transmits torque in the circular protruding part (in the leaflet). This design makes use of the external drive system to the highest degree, so that the torque can be exerted to the extreme. The transmission of high torque does not change the head itself.

Second, commonly used conical bearing surface bolts and different head types of bolts

Flat-top countersunk head: The standard angle is 80~82 degrees, used for fasteners whose surfaces need to be tightly joined. The bearing surface can provide good centering.

Oval Countersunk: The full name is Oval Countersunk. This head shape is similar to the standard flat countersunk, but it is more widely used. In addition, a round, neat upper surface is more attractive in design.

Small flat top countersunk head: Same as the standard flat top countersunk head, oblate countersunk head, the head angle is 80~82 degrees, but the head part should be 1/3 smaller, used for simple products or particularly short length. To be more specific, it is used for standard countersunk holes and is very suitable for tight fitting parts.

Flat top countersunk head (100 degree countersunk head): This special flat top countersunk head screw is gradually being applied to surfaces that require a close fit. It is recommended to be used on soft materials to break down the pressure on the surface with larger and less angles. Suitable for aluminum, soft plastics, etc.

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