Cold heading is a metalworking process for shaping blanks into highly shaped or designed parts without using any heat. This is achieved by a reciprocating ram that forces a punch into a preformed die, known as a header. This machine allows for a high production rate of intricately shaped fasteners such as nuts, bolts and screws, as well as many other products such as hinge pins, wing nuts, hanger bolts and security screws. Unlike traditional metal cutting operations, which can generate as much as 60% waste, cold headed components can be produced with tolerances close to +/-.002″ with no secondary operations.
The first step in the process is forming the metal blank to the desired shape, usually done by upsetting or hammering. This is also known as cold forming, although hot forming can be used in some cases. During this stage, the blank is shaped into a cylinder that will become the center of the fastener head. For a bolt or screw, the cylinder is typically larger in diameter than its length. This is a critical step in the process because if the material is too thin, it can be easily fractured or cracked during the upsetting process. If it is too thick, it may not be possible to use the cold heading process because of limitations on the amount of force that can be applied.
After the cylinder is formed, the punch is transferred into the die and the next blow of the ram forms the fastener into its final form. The resulting fastener is then either trimmed or pierced depending on its end application. For example, a hex head screw requires two strikes of the ram to achieve its final form, but a wing nut may only require one strike. This is because the hex head has more than two diameters of space inside it, while a wing nut has less than two diameters of space inside it.
There are several different types of headers, from single-die two blow to multi-die six blow machines. Each type is designed to produce a specific product, such as a hex head screw or a butterfly screw. The machines are also available with various options and accessories for the production of non-standard products, including thread rolling, swaging and abrasion resistant coatings.
Other accessories include a floating inspection system, an overload protection and lightload stop system, and a transfer system with adjustable speed to control the feed rate of the slug. The headers are sold as kits that include the necessary tooling for each type of fastener. The kits contain the headers, transfer presses, hammers, dies and a manual that contains detailed instruction on set-up and operation. Purchasing the complete kit saves time and money as the buyer does not have to buy each piece of equipment separately. Also, the kit eliminates the cost of modifying existing equipment to handle new or specialized applications. This makes it easier for manufacturers to switch between production lines or add a new line of products with minimal downtime and loss of productivity. Heading machine