The majority of our hot wound coil springs are manufactured from a Micro-alloyed spring steel (grade X4K92M61S) produced by B.H.P or equivalent. This grade of spring steel gives our springs the ability to withstand high operating stresses, while also providing superior resistance to sag. Other grades including stainless steel and other specialty steels for specific operating conditions are also available on request. We produce our hot wound springs from either black or ground stock in diameters from 9.5mm to 65mm. For smaller diameter material see here.
We have a number of flexible coil spring winding plants able to produce just about any size of coil spring you require. Our computer controlled coil spring winding machine designed and built in-house is capable of hot winding variable pitch coil springs in material up to 25 mm. The winder is powered by its own self contained hydraulic power pack. Each different springs specs. are entered into a custom written program and then downloaded to the machine from a database by the operator prior to winding. Once the machine has received the data the operator is only required to feed heated spring steel bars to the machine and then remove the completed spring ready for heat treatment.
All ends are tapered and hot stamped prior to rolling. Rolling of the springs is performed as a hot process, then the springs are heat treated (oil hardened & tempered), shot peened, and scragged. For a step by step exclamation of our hot wound coil spring manufacturing process see here.