Why Are Cold-Headed Rivets Stronger than Screw-Machined Parts?
Posted by: Admin | Date: 27-10-2016
Cold-head rivets are known to be stronger than screw-machined fasteners for a variety of reasons. One of those reasons relates to work hardening. As the metal is maneuvered around during the process of cold heading, work hardening occurs each time the metal is struck. Softer materials such as brass and aluminum become stronger as they make their way through each dye. Some stainless steel grades do not respond, regardless of the type of post-heat treatment used. Cold heading stainless steel fasteners results in an even stronger part.
Cold-head rivets also benefit from better material. This is due to the fact that the material used in the cold-heading process is designed specifically for use in upsetting and extrusion. Overall, the metal used for cold heading is typically a higher grade of material than that used for screw machining. This results in a better-quality product.
While screw machining does offer some advantages, cold heading utilizes specific technology to form fasteners as close to the net shape as possible, while simultaneously offering cost savings. Furthermore, although screw machining tends to generate a tremendous amount of scrap, that is not the case with cold heading.
With that said, not all parts are the best candidates for cold heading. Some parts are actually better candidates for screw machining due to their innate characteristics. For instance, parts that have little to no head-to-shank ratio, those without a unique shape, parts without recesses, and short parts are all usually better left to screw machining. When low volume is required, screw machining may also be a better choice.
Even so, cold heading is recognized as a leading method for cost savings. While screw machining can result in scrap losses of up to 75 percent, cold heading typically results in a scrap loss of 3 percent or less. When the fact that cold heading also produces an extremely smooth surface finish is taken into consideration, it becomes clear that cold-headed parts, including cold headed rivets, are the preferred choice for many projects.