1797, Maudslay invented the all-metal precision screw lathe in London. The following year, Wilkinson made a nut and bolt making machine in the United States. Both machines can produce universal nuts and bolts.
1836, Henry M. Philips applied for the patent of cross slotted head screw, which marked the great progress of screw basic technology. Different from the traditional slotted head screw, the edge of slotted head screw.
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There are many commonly used screw materials, roughly two kinds, one is carbon steel, that is, iron. Carbon steel can be divided into low carbon steel, medium carbon steel and high carbon steel. The other is made of stainless steel, such as stainless steel SUS20 1.304.3 16 06, and so on. 39666 . 86666666667
The quality of the screw material determines the quality of the screw itself to some extent. Therefore, manufacturers in the screw industry must choose good quality screw materials for production. Now the quality of screws can be better guaranteed.
Size, mechanical properties and surface defects. The specific inspection items of each part have different regulations according to different products. For example, the dimension inspection item specifies the hexagon nut as thread gauge, thread stop gauge, thread diameter, opposite width, diagonal dimension, nut height and verticality between nut bearing surface and thread axis.
References:
Baidu encyclopedia-screw