Fastener Grades Question
07-08-2005, 09:43 PM
#1
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Fastener Grades Question
Can anyone tell me what the markings mean on these two nuts. One it the an official Porsche nut for the crank girdle, the other is a potential replacement I'd like to use. Anyone know what the markings mean?
07-09-2005, 02:28 AM
#4
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Originally Posted by Chris Prack
Do yourself a favor and just order them from Porsche. Remember this could be a few more steps back than two!!!
07-09-2005, 03:05 AM
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The one on the left is a grade 12 nut which is indicated by the |12| on it. These are fairly uncommon, the one on the right is a grade 8 which is indicated by the |8| on it that one is a dime a dozen at anywhere that stocks metric fasteners.
With metric nuts they don't put the .8 or .9 suffix on them like they do with bolts. No way I'd use an 8 where a 12 is used originally unless I was stranded in the desert and it was only a temporary measure and somewhat of a do or die type situation. To put it into perspective, the OEM head nuts are grade 10 nuts which can be found if you look for them, but most of the ones you're going to find even in a store with a decent metric selection are going to be the grade 8 nuts or if you're lucky they might keeps some grade 10 nuts in stock.
You *might* be able to find some from Maryland Metric, their website is www.mdmetric.com but if they don't have any grade 12 nuts, I think you'd be well advised to wait. Probably not what you were hoping to hear.
As for the other marks, the Z like mark on the nut on the right is the manufacturer's symbol as is the one at the top on the real deal. I'm not sure who the manufacturer is on those but just think of them as a cattle brand of sorts including the inherent oddness of a brand.
With metric fasteners, the first number before the dot is the ultimate tensile strength the bolt is rated for in Mega Pascals so ~ 800 MPa for a grade 8 metric, and the second number is the yield strength's percentage of the ultimate tensile strength so the trailing .8 means that the yield strength is 80% of the ultimate tensile strength. For a 10.9 and 12.9 fastener you're looking at ~1000 MPa ultimate tensile strength with yield strength being 90% of that or 900 MPa and for a 12.9 it's ~1200 MPa and a yield strength of 1080 MPa.
A metric grade 8.8 bolt is usually a carbon steel whereas grade 10 and 12 or higher ones are generally an alloy steel. The same principle applies with nuts other than they don't bother with the yield strength when rating them.
So now that you know the difference, that means that the grade 12 nut has almost twice the ultimate tensile strength that the grade 8 one does. Given the somewhat critical location these are in do you really want to take the chance? See what the grade is on the M10 nuts. If you can find an equivalent grade nut in the right thread pitch, go for it, you should be fine. If it's also a 12 and you've only got the 8, I'd say you'd be much safer overall reusing the old ones that are the correct grade vs. using a new nut that's not up to the task. Unless you really beat the crap out of the threads or flats taking it off, it's probably in decent shape anyway. If you put the old nuts you're thinking of using on the threads and they don't show signs of being really loose, it's probably fine, try to pick the ones that seem to have the least play on the threads at the very least.
Bottom line is:
There's no way in hell I'd go from a grade 12 nut to a grade 8 nut in an application with the potential to seriously grenade the engine. Down time sucks, but having to redo a whole engine because of an "oops" like that sucks considerably more in my opinion. I can't imagine Porsche went to the trouble to spec a grade 12 nut just for kicks, they're just not something commonly seen. Granted Porsche engineers do occasionally tend to over do it a little, but I don't think that's the case here at all.
With metric nuts they don't put the .8 or .9 suffix on them like they do with bolts. No way I'd use an 8 where a 12 is used originally unless I was stranded in the desert and it was only a temporary measure and somewhat of a do or die type situation. To put it into perspective, the OEM head nuts are grade 10 nuts which can be found if you look for them, but most of the ones you're going to find even in a store with a decent metric selection are going to be the grade 8 nuts or if you're lucky they might keeps some grade 10 nuts in stock.
You *might* be able to find some from Maryland Metric, their website is www.mdmetric.com but if they don't have any grade 12 nuts, I think you'd be well advised to wait. Probably not what you were hoping to hear.
As for the other marks, the Z like mark on the nut on the right is the manufacturer's symbol as is the one at the top on the real deal. I'm not sure who the manufacturer is on those but just think of them as a cattle brand of sorts including the inherent oddness of a brand.
With metric fasteners, the first number before the dot is the ultimate tensile strength the bolt is rated for in Mega Pascals so ~ 800 MPa for a grade 8 metric, and the second number is the yield strength's percentage of the ultimate tensile strength so the trailing .8 means that the yield strength is 80% of the ultimate tensile strength. For a 10.9 and 12.9 fastener you're looking at ~1000 MPa ultimate tensile strength with yield strength being 90% of that or 900 MPa and for a 12.9 it's ~1200 MPa and a yield strength of 1080 MPa.
A metric grade 8.8 bolt is usually a carbon steel whereas grade 10 and 12 or higher ones are generally an alloy steel. The same principle applies with nuts other than they don't bother with the yield strength when rating them.
So now that you know the difference, that means that the grade 12 nut has almost twice the ultimate tensile strength that the grade 8 one does. Given the somewhat critical location these are in do you really want to take the chance? See what the grade is on the M10 nuts. If you can find an equivalent grade nut in the right thread pitch, go for it, you should be fine. If it's also a 12 and you've only got the 8, I'd say you'd be much safer overall reusing the old ones that are the correct grade vs. using a new nut that's not up to the task. Unless you really beat the crap out of the threads or flats taking it off, it's probably in decent shape anyway. If you put the old nuts you're thinking of using on the threads and they don't show signs of being really loose, it's probably fine, try to pick the ones that seem to have the least play on the threads at the very least.
Bottom line is:
There's no way in hell I'd go from a grade 12 nut to a grade 8 nut in an application with the potential to seriously grenade the engine. Down time sucks, but having to redo a whole engine because of an "oops" like that sucks considerably more in my opinion. I can't imagine Porsche went to the trouble to spec a grade 12 nut just for kicks, they're just not something commonly seen. Granted Porsche engineers do occasionally tend to over do it a little, but I don't think that's the case here at all.
07-09-2005, 03:20 AM
#6
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z3bra --
I nominate that as answer of the year. Thank you for taking the time to lay that out for me. I was looking for bolt-type grade markings (like 10.9), and could not make sense of these nuts. Your info is like a flood light in the dark -- thanks again. I'll take a look at the used ones, and probably end up waiting for all new nuts from Germany. Plenty of other stuff I can be doing on the motor in the meantime anyway, I suppose.
I nominate that as answer of the year. Thank you for taking the time to lay that out for me. I was looking for bolt-type grade markings (like 10.9), and could not make sense of these nuts. Your info is like a flood light in the dark -- thanks again. I'll take a look at the used ones, and probably end up waiting for all new nuts from Germany. Plenty of other stuff I can be doing on the motor in the meantime anyway, I suppose.
07-09-2005, 04:29 AM
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No problem at all, I'd just hate to see someone potentially shoot themselves in the foot like that when it comes to engine internals. Our parts are plenty spendy as it is without having to buy them twice because of skimping on a fastener.
Places to never cut corners fixing a car:
Engine internals. Probably won't get anyone hurt but it will bite you in the wallet pretty badly.
Suspension, brakes, and steering systems. Might get you hurt or killed if it fails, might also get someone else that just happens to be in the wrong place at the wrong time hurt or killed too.
Fuel related parts. Engine fires are generally frowned upon in the eyes of an automotive enthusiast, particularly on the car for which they're an enthusiast. Burning to death is generally frowned upon as well.
Seat belts, roll bars, other safety equipment. The best restraints in the world are useless if you don't have them mounted right.
Other stuff you can squeek by with lesser substitutes if you feel comfortable with it, it might not be a good idea, but sometimes the situation demands it.
Stuff that's pointless to be a cheapass about. Things like the thermostat and coolant tank cap on our cars. Take my car, the previous owner's mechanic threw some aluminum POS thermostat in there and it had a good 1/8" or more play in it. It didn't have the outer rubber ring with the groove in it installed. I mean c'mon is the extra 6 bucks for the real brass thermostat that much of a factor? Is some POS stant radiator cap that's 5 bucks instead of 10 or 11 like a real Behr one that big of a factor? Nothing wrong with the Stant caps themselves per se other than they usually are the wrong pressure rating for our cars (too low). Little crap like that really pisses me off. Nothing wrong with trying to get the best value and deal you can, but I hate finding those sort of gotchas on my car courtesy of one or more of the cheap bastards that previously owned it.
Oh well, I'm going to crash so I can get up to work on the garage queen poster child for scope creep itself in the morning while it's still tolerable out there. Garage work in Phoenix in the summer really, really sucks.
Places to never cut corners fixing a car:
Engine internals. Probably won't get anyone hurt but it will bite you in the wallet pretty badly.
Suspension, brakes, and steering systems. Might get you hurt or killed if it fails, might also get someone else that just happens to be in the wrong place at the wrong time hurt or killed too.
Fuel related parts. Engine fires are generally frowned upon in the eyes of an automotive enthusiast, particularly on the car for which they're an enthusiast. Burning to death is generally frowned upon as well.
Seat belts, roll bars, other safety equipment. The best restraints in the world are useless if you don't have them mounted right.
Other stuff you can squeek by with lesser substitutes if you feel comfortable with it, it might not be a good idea, but sometimes the situation demands it.
Stuff that's pointless to be a cheapass about. Things like the thermostat and coolant tank cap on our cars. Take my car, the previous owner's mechanic threw some aluminum POS thermostat in there and it had a good 1/8" or more play in it. It didn't have the outer rubber ring with the groove in it installed. I mean c'mon is the extra 6 bucks for the real brass thermostat that much of a factor? Is some POS stant radiator cap that's 5 bucks instead of 10 or 11 like a real Behr one that big of a factor? Nothing wrong with the Stant caps themselves per se other than they usually are the wrong pressure rating for our cars (too low). Little crap like that really pisses me off. Nothing wrong with trying to get the best value and deal you can, but I hate finding those sort of gotchas on my car courtesy of one or more of the cheap bastards that previously owned it.
Oh well, I'm going to crash so I can get up to work on the garage queen poster child for scope creep itself in the morning while it's still tolerable out there. Garage work in Phoenix in the summer really, really sucks.
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07-09-2005, 12:22 PM
#8
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z3bra, thanks and agreed. I was just trying to find a replacement for the nuts that are currently unavailable, but I am taking no chances for money-savings purposes. I have three sets of main bearings and two sets of pistons to prove it. 
Maybe I'll take the opportunity to order up a complete set of new fasteners like Rolexnj did. I'd do it in a second if I had a complete list of fasteners. Anybody have a list? Here is a pic from Rolex's website:
Maybe I'll take the opportunity to order up a complete set of new fasteners like Rolexnj did. I'd do it in a second if I had a complete list of fasteners. Anybody have a list? Here is a pic from Rolex's website:
07-09-2005, 02:13 PM
#9
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Hey Tom
I think I can locate those ?
I will call on Monday for you
Hey Brian ... One thing no one could ever say about you...
That is, that the answers you give lack content or functional understanding
Regards guys
Ed
I think I can locate those ?
I will call on Monday for you
Hey Brian ... One thing no one could ever say about you...
That is, that the answers you give lack content or functional understanding
Regards guys
Ed
08-08-2005, 03:30 PM
#13
Tom, I had to buy a whole box. If you want some let me know.
08-08-2005, 07:08 PM
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Originally Posted by Fen
Hey! You leave my car alone! 
If it makes you feel any better I just finished torquing down my oil pan so however bad your car is, it could be worse. I need to get the beast done by about the 20th or so since my school starts up again on the 22nd and then I'll probably be hurting for time to work on it.
On the subject of fasteners here I even drilled the oil pan bolts for safety wire except for the 4 long ones at the front and back of the pan. I would have got those too but I didn't feel like pulling off the captive washer and they don't usually seem to be the ones near leaks anyway.
