Is the head of bolt formed by puching? 

Yes, most of the heads of bolts are punched, because this is the most commercial way. Factories can use hot forging or cold forgine to form the heads. 

 But sometimes for small quantities, some specified head bolts are shaped by turning machine/ lathe. 

What is COLD HEADING ? 

The process of progressively forming a specified shape from metal wire without adding heat - using a replicated series of dies, hammers , and punches at high speed. 

Simply put: cold heading is feeding wire into a machine, cutting it into pieces, and hammering on it. The material is not heated or machined, but formed into its desired shape at room temperature.

What is hot heading? 

 Hot heading, also known as hot forging, is the process of heating material to a particular temperature and ten forming it into a desired shape. 

 When bolts' diameter larger than M24, the heads have to be hot forged.

Anyang Longteng Hexagon Bolts are all hot forged, as we only supply big construction bolts, with range M30~M72, class 8.8, 9.8, 10.9, 12.9 high properties.