Difference between GB30 bolt and GB21 bolt.

　　Difference between GB30 bolt and GB21 boltThe above conclusions show that insert nut To a great extent, it can bring new vitality to the market and make the industry develop well. https://www.hengkefasteners.com/

　　

　　GB30 bolt and GB21 bolt are common hexagon-head bolts, which belong to the 1976 standard. It is called “zero bolt and two bolts” in the market. This standard has been invalidated and replaced by new standards such as GB5782 and GB5783. But the products are still in circulation in the market, so they are also called old standard bolts.

　　

　　Remarks: GB5782 and GB5783 only specify the appearance, size, thread, surface and other data of bolts, but do not require the material, so the standard cannot determine the grade of bolts.

　　

　　Standard GB5783-86

　　

　　The opposite side and thickness of hexagon head of GB30 bolt are larger than that of GB21 bolt, so sometimes bolts with the same diameter will appear, and wrenches with different sizes are needed. GB21 bolt is also called small head bolt.

　　

　　For example, a bolt with a diameter of M12 has a hexagon head thickness of 8 0.29 in GB30, 18.72-19 on the opposite side, 7 0.29 in GB21 and 16.76-17 on the opposite side.

　　

　　Note: Some people say that the replacement standard of GB30 bolt and GB21 bolt is GB5780/1. This statement is wrong. GB5780 and GB5781 replace GB5 (Rough wool bolt), which is often called “wool bolt” in the market. (as shown in the figure below)