fastener fitness

[deckard]

i received an order for parts for an engine rebuild from an established and reliable source. the con rod nuts that came with the order have no markings - neither grade nor manufacturer - on them.
my reflex, then, is to think of them as no more than a grade 2 hardness where, as i understand it, grade 2, or less, requires no markings. the ones that came off the connecting rods, which are the originals, do have the expected markings which, of course, only adds to the perplexity.
is this a new thing in the world where high grade nuts can have no markings on them?
and, to me, new would probably be anything that has happened over the last 20 years.
thanks

[Dpmulvan]

Sign of the times, probably made in China like everything else.

[PeteKz]

Curious. You ordered just the nuts and not the nuts and bolts? They are usually sold as a set. Is this for a Porsche? What brand bolts and nuts?

A bit about the engineering of nuts and bolts: The nuts are almost always more malleable than the bolts. Grade 8 bolts and higher are very hard and strong, and the threads maintain their shape. The nuts, however, are designed to be softer so as to conform to the threads on the bolts, and not vice versa. Slight deformation allows the threads to be fully engaged and locked up for maximum strength of the pair. IN many vehicle manuals (other brands than Porsche), you will see instructions to discard the nuts, but not the bolts, and this is why. The idea is that fresh nuts can conform better to the harder stronger bolts. The old nuts may have become work hardened and not as malleable or maybe the manufacturer wants to be sure the torque value is not changed by the previous slight deformation of the nut.

However, from an engineering perspective, I don't see why that is necessary in most cases, even where new nuts are specified. If the old nut is installed and it torques to the specified value, it should hold just as well as a new nut, basically "forever." And I practice what I preach. For nuts that are supposed to be replaced, I frequently reuse them if I can't get the new ones quickly enough for the job I'm in the middle of. I haven't had those let go yet. But I'm not working on customers' cars, and if I were, I'd do it by the book.

That doesn't help understand the nuts you received. I would go back to the seller and ask about why no markings, and what the source was for those nuts.

About 30 years ago, the Army had a sudden problem with bolts breaking on the drive sprockets that drive the tread on tanks. It turned out that the supplier had sold a batch of bolts that were inferior. They had the documentation that said they were made to specification, but obviously, those were falsified. Buyer beware.

[deckard]

well ... it's a 912; the bolts are integrated with the rod caps so no new bolts.
they look good, good color and even threading but no markings of any kind
which is why i am wondering.

[callard]

912 and 356 rod nuts sold by Stoddard and others come in a package labeled 50203114. The eight nuts themselves have no markings on them. The work very well.

[deckard]

yes, that's the part number on the package.
so, good. i can stop worrying about application but
i will still be curious about the missing markings.

[PeteKz]

If they torque to spec, don't worry about it.

[Jeff Alton]

It is common for a nut to NOT have a grade rating stamped on it..... New connecting rod nuts from Porsche for the 6 cylinder aircooled motors do not have a stamp on it.

The bolt, that stretches under torque, is what has the grade marked on it.

Cheers

[porschedude996]

Originally Posted by deckard

yes, that's the part number on the package.
so, good. i can stop worrying about application but
i will still be curious about the missing markings.

These are specialty nuts/hardware. There is no requirement to place an SAE bolt marking on the piece. (No dash/grade 1, one dash/grade 2, two parallel dashes/ Aluminum low shear bolts, two dashes in radial position stainless steel, three dash/grade 5, six dash/grade 8). SAE or general Aircraft Standard markings are for common general use. Car, Tractor, process machines, etc. Some manufacturers will put their own makers mark or logo for identification. And no markings fine, as long as the source is reliable. China made flags a warning to me.