How To Choose Fish Bolt? | FASTENER EURASIA MAGAZINE
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How To Choose Fish Bolt?

The fish bolt is a rail fastener that is used with rail joint. There are various types of fish bolt on the railway material market, the customers can select suitable and applicable fish bolt to buy. But for a part of new buyers, they don’t know how to choose fish bolt. As a professional railway fastener manufacturer, AGICO Rail compare common fish bolt and high-strength insulating bolt to help you to know the fish bolt better and choose fish bolt easily.
 
The material of fish bolt is low carbon alloy steel or medium carbon steel and after heat treatment (quenching, tempering), known as high strength fish bolt. The rest are called common fish bolts. High-strength fish bolts are made of high-strength steel or require large pre-tightening force.
High-strength insulating bolt is used to fasten steel rails. It is a kind of rail fastener such as rail clip, track spike, screw spike, tie plate, rail joint bar, etc. High strength fishtail bolts have several grades such as 8.8, 9.8, 10.9 and 12.9.High strength fish bolts are mostly used for the connection of bridge or steel rail.
 
High-strength insulating bolt and fish bolt are two common types of rail bolt. They are both used to fix steel rails, and what’s the difference between high-strength insulating bolt and fish bolt?
 
Comparison of high-strength insulating bolt and fish bolt
 
High strength fish bolts are designed to withstand loads greater than normal bolts of the same specification. The ordinary fish bolts are made of Q235 (A3). In order to distinguish high-strength fish bolts and ordinary fish bolts, and we will compare and analyze the differences between them through multiple aspects.
 
• From the view of material, the high strength fish bolt uses the high strength material to manufacture. Bolts, nuts and washers are made of high strength steel, such as 45 steel, 40 boron steel, and 20 manganese titanium boron steel, 35CrMoA. Ordinary bolts are usually made of Q235 steel.
• From the view of strength grade, the high strength fish bolt has been widely used. Two common intensity grades include 8.8s and 10.9s , of which 10.9 is the most common. The strength of ordinary fishtail bolts is much lower in grades 4.8, 6.8 and 6.8. 
 
• According to the characteristics of the force, the high strength fish bolts apply pretension and transmit external force by friction. The normal fish bolt is connected by the shear resistance of the bolt rod and the pressure of the hole wall to transfer the shear force. The pretension produced when tightening the nut is very small and its influence can be ignored.
 
• From the view of use of fish bolt, common fish bolts can be reused, but high-strength fish bolts cannot be reused. High strength bolts are generally used for permanent connections. The high strength fish bolt is the pre-stressed bolt, the friction type torque wrench applies the specified prestressing force, the pressure type twists off the plum head. The common fish bolt has poor shear resistance and can be used in the secondary structure. Ordinary fish bolts only need to be tightened.
 
In conclusion, high-strength fish bolt connection has the advantages of simple construction, good mechanical performance, removable, fatigue resistance, and not loose under the action of dynamic load, in a word, itis a very promising connection method. The high strength fish bolt uses the specially-made wrench to tighten the nut, the bolt produce the huge but the controlled pre-tension, through the nut and the pad, also apply same pre-pressure to the connected piece.
 
Source: Agico Group