| Watts Shop Performance |
| True Billet Steel Rods |
| True billet rods are fairly uncommon in todays marketplace. Manufacturing begins when rough shapes are flame cut from a plate of premium quality forged high carbon steel (usually SAE 4340), then finish machined to the required final specifications. Similar to cutting a pattern from a sheet of cloth, manufacturers benefit from true billet rods because they do away with the need to make expensive forging dies. These dies can cost between $35,000 and $45,000 a pair and several may be needed to fit all the various applications in the hot rodding galaxy. On the contrary, the dimensions and physical characteristics of a true billet rod are only limited by the size of the plate it will be cut from. Although the rolling process that creates the plate of parent material gives a uniform, longitudinal grain flow with excellent molecular bonding properties for outstanding strength, there is one minor shortcoming. True billet rods lack the circular grain flow inherent to the big end of forged steel rods. Instead, the longitudinal grain flow continues undisturbed throughout the shoulder and the cap sections. This does compromise some strength, but industry experts say it is a minor issue and is responsible for, at worst, 15% reduction in the ultimate hoop strength of the bearing hole. On the positive side, true billet rods are inherently free from the surface degradations caused by the forging process. A fully machined billet rod has virgin, high quality material of uniform composition all the way from the core to the external surface. This makes it more resistant to the formation of cracks, a detail that more than makes up for the stubborn grain flow at the big end. |