Rambuck
01-04-2014, 01:06 AM
Bought an overstock crank out of the Smyrna, TN plant yesterday. It has LETTERS for the main journal grades. 64914 Letters are LKMN. This is for a VQ30/35 block, p/n 12200-2Y902. 64915
So, I'm wondering if anyone else has come across letter grades and what they mean. Thought perhaps they might follow the usual pattern: A=0, B=1... Which puts K=10. Hey, this seems like Nissan's way of using double-digit grades. REALLY?? 60 microns off in production... Perhaps why it was overstock? Well, figured I would mic it before sending it back. Turns out, the mains measure sequentially 2.36060", 2.36050", 2.36045", and 2.36040". The precision on that last digit is 0.00005". Measured with Mitutoyo 2-3" mic zeroed with 2" cal standard. Also hit 1.00000" with a 3" cal standard so I trust the absolute accuracy matches the precision. The mic has a force ratcheting knob, and reproduced the same measures on several successive tries on different points. So, that puts the respective grades at 2233. Why not stamp the crank appropriately?? Was there some error with Nissan's profilometer? The sequence of letters isn't quite right. My measurements show a slight monotonic taper rather than an undulation. KLMN might have been more appropriate.
Is there anything else to the letter grade? What's missing here?
How about runout? I didn't place this crank on a spindle and measure each journal to a fixed common axis. Would I truly measure in the double-digit grades? Possibly I think. Is this a bad crank? Total runout spec is higher, 100 microns, so this crank still meets Nissan's overall spec. I'm just surprised to see runout entering the journal grade. Don't think it should.
Any Nissan machine gurus out there? Any Nissan service technicians experts? Please help solve this riddle.
Thanks.
Sent from my iPhone using Tapatalk (http://tapatalk.com/m?id=1)
So, I'm wondering if anyone else has come across letter grades and what they mean. Thought perhaps they might follow the usual pattern: A=0, B=1... Which puts K=10. Hey, this seems like Nissan's way of using double-digit grades. REALLY?? 60 microns off in production... Perhaps why it was overstock? Well, figured I would mic it before sending it back. Turns out, the mains measure sequentially 2.36060", 2.36050", 2.36045", and 2.36040". The precision on that last digit is 0.00005". Measured with Mitutoyo 2-3" mic zeroed with 2" cal standard. Also hit 1.00000" with a 3" cal standard so I trust the absolute accuracy matches the precision. The mic has a force ratcheting knob, and reproduced the same measures on several successive tries on different points. So, that puts the respective grades at 2233. Why not stamp the crank appropriately?? Was there some error with Nissan's profilometer? The sequence of letters isn't quite right. My measurements show a slight monotonic taper rather than an undulation. KLMN might have been more appropriate.
Is there anything else to the letter grade? What's missing here?
How about runout? I didn't place this crank on a spindle and measure each journal to a fixed common axis. Would I truly measure in the double-digit grades? Possibly I think. Is this a bad crank? Total runout spec is higher, 100 microns, so this crank still meets Nissan's overall spec. I'm just surprised to see runout entering the journal grade. Don't think it should.
Any Nissan machine gurus out there? Any Nissan service technicians experts? Please help solve this riddle.
Thanks.
Sent from my iPhone using Tapatalk (http://tapatalk.com/m?id=1)