Cold heading machine is a mechanical manufacturing process that uses powerful hammers and dies to transform a piece of metal into a shaped part without adding heat to the material. It creates stronger pieces with closer tolerances and less waste than machining. This technique can be used on many different types of materials, but the best results are often achieved using high-quality steel such as quenched and tempered alloy structural steels or low-temperature tempered alloy steels.
The first step in the cold heading process is to take a large coil of wire and pull it through a draw box to change its diameter to the desired size for the finished fastener. A wire straightener may also be used to correct the angle of the end of the fastener if needed.
Once the wire is the right length, it will be fed into the cold heading machine. Inside, it will travel through a tooling progression and pass into the headstock where it is surrounded by punches and dies. The punches transfer the required force to the slug and provide close dimensional control on internal part features. The dies confine and guide the slug while it passes through the machine, shaping it into the shape of the finished product.
The process of cold forming, which is also known as cold heading, forms the material in progressive steps into net or near net shaped parts. The starting slug of material is typically the same volume as the finished part and does not require cutting which eliminates waste and reduces production time. The process can also be used to increase or decrease the feedstock’s diameter, and its length can be varied by piercing and trimming.
In addition to heading, other cold forming operations include upsetting and extruding. These can be combined with heading to produce more complex, multi-faceted fasteners that would not be possible with a single operation. Improved machinery, increased metallurgical knowledge, and higher grade alloys have made these processes more capable than ever of producing high quality, durable fasteners. However, it is important to keep in mind that cold forming is a forming process rather than a stamping one and does not produce as much strength as a screw machined part. This is because the slug of material cannot be driven as far into the die as it could with the same amount of heat, and certain materials will not work in this method at all. Therefore, secondary operations like rolling or forming will often be required on more complex parts. This is especially true for items like bolts and screws, where the overall length of the fastener will be significantly longer than its diameter. This is why these parts are often called “long-skinny” fasteners.