Fish Bolts classification
2021-09-25
According to the force mode of connection,it can be divided into ordinary and reamed holes.According to the head shape points:hexagonal head,round head,square head,countersunk head and so on.The hexagonal head is commonly used.Countersunk heads are generally used where connections are required. 
Railway Fish Bolts and Nuts are divided into eight grades according to the performance grade:3.6,4.6,4.8,5.6,5.8,6.8,8.8,9.8,10.9,12.9.Bolts of grade 8.8 and above(including grade 8.8)are made of low-carbon alloy steel or medium carbon steel and treated with heat treatment(quenching+tempering),generally known as High Strength Bolts.Below grade 8.8(excluding grade 8.8)are generally called ordinary bolts. Ordinary bolts can be divided into A,B,C three grades according to the production accuracy,A,B for refined bolts,C for coarse bolts.For connecting bolts used in steel structures,unless otherwise specified,they are generally C bolts of common rough manufacture.There are differences in different processing methods,usually corresponding processing methods are as follows: (1)The bolt rod of grade A and B bolts is processed by the lathe,and the surface is smooth.The material performance grade is 8.8,the production and installation is complicated,the price is high,and it is rarely used; (2)Class C bolts are made of unprocessed round steel,and their material properties are grade 4.6 or 4.8.Large deformation in shear connection,but convenient installation,low production cost,mostly used for tensile connection or installation of temporary fixation.
