| Hey all, some fun stuff from member itsa300ZX who gets to break stuff for a living... enjoy! Subject: Nissan VG crankshaft from a 300zx Z32. To determine the case depth hardness of bearing journal surfaces. These cranks are factory nitrided at the bearing journals. The following are facts as found; take the information as is and make your own opinions. All measurements taken are with calibrated equipment to meet ISO 17025 quality programs. Crankshaft is from an unknown year Z32 block that was sent to IPP for a stage III build. Polished and balanced. Later, #5 bearing was spun and the crank was removed and replaced: 
Crank shaft sample. Rod journal 4 was measure to have an OD of 49.969 and 49.965mm taken at mid width and 90 degrees to each other. (Thanks to Vopalz for supplying the test piece) Area of interest: Rod bearing journal 4, for convenience. (tail end of arrow)
 Some cutting action for ease of handling: 
Sample ready for mounting and polishing. Sectioned through an oil hole: 
In the press it goes: 
10 minutes later, out it comes 
A little grinding and polishing, yields a mirror finish 
Same picture above with a 2% Nital etch to reveal microstructure and OD case 
Photo micrograph of journal cross-section, note the hardness(6) indentations, black diamond shaped: 
1st indent at 0.002” harness of 564 Vickers.
2nd at 0.005” hardness of 438 Vickers
3rd at 0.007” 498 Vickers
4th at 0.010” 498 Vickers
5th at 0.015” 374 Vickers
6th at 0.039” 289 Vickers
I’ve done a coupe in the core (not shown in picture) 260 and 250 vickers. ..more info in the discussion below on what these numbers mean. Higher magnification photo same as above. Microstructure consists of Cementite, Pearlite and Ferrite: 
Discussion: Well what the hell does this all mean? Basically to answer the question, “how much can the VG crank be ground before journal wear resistance becomes an issue?"
Here we are using the Vickers hardness scale, as is has a broad range that covers hard to soft metals and the fact that we can precisely test the microstructure of interest. Industry standards call for case depths measured to a hardness of 50HRC (Rockwell Hardness scale C) for wear resistance components (ie, bearing races, journals etc) ASTM conversion of approx 514 vickers. As you can see in the results, at a depth of 0.010”, we are already below the norm. Hope this helps. Part 2 to follow, main bearing journal. itsa300zx
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Z32 Cranky Facts Part I - 
