Concentricity of the bores is critical to ensure friction free runout relative to the piston pin and crank journal.

Concentricity of the bores is critical to ensure friction free runout relative to the piston pin and crank journal. Twist and bend in the automotive world is often associated with the quality of connecting rods. Oliver goes well beyond these simple concepts and fully defines the relationship between the pin and crank bores.

As one of the most challenging measurements in GD&T, concentricity is obtained through in-process air gauging, verifying that Oliver rods adhere to the highest accuracy standards. Air gauging, described in detail below, is an extremely precise measurement device for this particular feature. Even better than the most accurate coordinate measuring machine (CMM), air-gauging effectively monitors concentricity of every Oliver rod. Since World War I machinists have used jig borers to ensure accuracy of bores. Through Oliver’s multi-step GD&T governed process, we have developed a modern day systemic version of the jig borer specific to connecting rods. This confirms that every Oliver rod has met our strict tolerances.

It seems like this would be a common practice for all connecting rod manufacturers. However, modern machining practices allow some manufacturers to cut corners and create concentricity of the bores through the honing operation, a function and tolerance never intended for any hone machine.

At Oliver concentricity is built into the part throughout our multi-step process, ensuring that the hone operation is correctly utilized to impart the final surface finish optimized for lubrication. Because extremely small tolerances, reaching beyond visibility, are often taken for granted, it is what we cannot see through conventional measurement techniques, that makes Oliver rods stand above the rest.

Ultimately, our commitment to achieving exact measurements between the pin bores and intangible axis surfaces of our connecting rods is only possible through GD&T. We are confident in our rods’ ability to reduce frictional loss to the absolute minimum amount, directly improving engine durability, performance and longevity. Most importantly, it allows the entire reciprocating assembly to be more efficient and ultimately generate more power.