It is composed of eight items such as the surface treatment of the separator. The new standard will be marked according to the new standard, and the product name and standard record items will be supplemented and refined into n items. Among them, the number of products and other numbers are separated by spaces. The number of specifications and sizes corresponds to the accuracy of the old standard. The words are separated by a multiplication mark x. Other diameters or characteristics of the other marked items, nominal length and The length of the thread is always separated by a short horizontal line. In this regard, the new, the old or the long pole is the old standard. The difference between the medium and the standard is that the old standard specifies the refinement of the standard number and other requirements. Therefore, the new standard is separated by spaces between the old ones, and the new standard is based on the standard, only the thread length or the length of the rod is separated by a dash. This avoids both standard and wrenching styles. The number in the number is in addition to the number in the subsequent size. According to the old standard, the product in the mark is confused. At the same time, the new standard also clearly stipulates that the name can not be omitted. In the case of misunderstanding according to the new standard, the separator symbol 1 can be omitted. The category (ie product name) 'cannot be omitted entirely, only this is not the old standard. Allow partial omitting.
Cylindrical pins, cotter pins and rivets are revised this time. For the chapter on marking examples, the nominal diameter of the fastener refers to its outer diameter, and the nominal shape of the conical pin has been adjusted. Some marking examples have been added. The old standard diameter refers to the diameter of the small end, and the nominal diameter of the retaining ring for the hole only gives the two types of fasteners, such as the bolt and the pin, a total of two indicating the diameter d of the retaining ring, and the nominal diameter of the retaining ring refers to the corresponding example. The new standard not only gives the nominal diameter of the bolt and pin marked shaft diameter d0, shaft end retaining ring and wire lock ring, but also gives the screw, nut, washer, self-tapping diameter Its outer diameter D and so on. Examples of markings for screws, rivets, and retaining rings. A total of 16 other diameters or characteristic examples are marked, covering almost all fasteners. This refers to the outside of the thread size or nominal size, making the marking example more comprehensive, representative, diameter or characteristic. Generally speaking, the rod diameter of the bolt and the outer part of the gasket are more conducive to the understanding of the standard provisions. The application of the f4 marking method for diameter, hole or shaft retaining ring outer diameter, rod diameter tolerance, etc., if required by design, should be noted for these diameters or related as previously described, a complete fastener marking including characteristics. Nominal length items such as category, standard number, thread size, or nominal size. To clarify the meaning of each mark, the correct application of the nominal length is generally a bolt, screw, stud, new fastener marking method, to avoid confusion of the mark is the pin and rivet and other rod fasteners, usually used The letters are very important.
The length of bolts and screws other than the head is called the length of the public category. The categories in the markings such as countersunk bolts, anchor bolts and countersunk screws refer to the name of the fastener product, and the overall length including the head is called For the nominal length, the live Chinese character indicates that it is only required to write a large class name. For example, the length of the lower part of the center line of the screw stud head is the nominal long bolt, which is divided into a square head bolt and a hexagon head bolt. When using six degrees. The overall length of the isometric stud is a nominal length. For the head bolts, for the category one, only the bolts with non-threaded parts at the end of the non-equal length studs can be marked. It is not necessary to mark the hexagon bolts because the length is the nominal length. The length of the split pin section is the nominal length. The bolt selected is the hex head bolt or the square head bolt. The degree of the other pins is the nominal length. The standard number in the mark can be known.
Steel box girder and steel and concrete composite box girder are used for large spans, which need to minimize the weight of the bridge, and their excellent high torsional stiffness is particularly useful. The clean lines of the box girder bridge usually have no obvious external hardening. It is generally considered to have excellent appearance and durability, and it has no traps for dust and moisture. Box-shaped cross-sections are sometimes used as compression members, such as in cable support structures or arched towers.
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