Here’s a clip of an aggressive heat treat/quenching process designed to allow maximum strength and hardness from this 4340 Nickel Alloy. This type of 4340 is also known for its elongation and fatigue properties post heat treating. This makes machining significantly more difficult, but when evaluated in terms of performance it is clearly superior to other alloy steels. This particular shaft tested a core hardness exceeding 43 HRC at the thickest cross section.
The featured video does little to show how complicated the shaft was to manufacture. Rough machining before heat treat was the only easy part. Meeting finish grind tolerances of .0004” +/- .00002”, that is four ten thousands of an inch concentricity across all bearing journals. Not to mention the shaft splines were timed with an interference fit. Using advanced alloys and understanding the material science behind various alloys has enabled Diversified Metal Products a tremendous advantage in effectively serving our clients with specialty shafts.