Traceability is not generally needed for part 91 N reg. It is largely a European money making treadmill needed to support the fees which part M firms pay to national CAAs.
There are very few “aviation” parts. A 145/21 company can buy almost any stuff, with a completely worthless certificate of conformity to cover its due diligence, and certify it and sell it for 10x more. I’ve known TB20s grounded for months while having the exact parts but without Form 1. It is a joke.
Thank you Antonio for the superb diagram.
Aircraft Spruce have at at least two incidences known to the public with counterfeit (and substandard) hardware items. This is probably because they are a general hardware store sourcing from many producers. I don’t know how much such a traceability document is actually worth in practice, but it’s probably more from Aircraft Spruce than from more specialized outlets.
Oooo, a few of the comets I read here are worrisome…
Sure, there are bolt applications in airplanes which are non critical, and if you have the data to demonstrate this, and a means to verify that an alternate choice bolt is adequate for that application, a fastener substitution approval may be appropriate. But, is it worth the worry about the bolt being “right” to save a few cents? Bolts are among the aircraft items which have been counterfeited in the past.
https://en.wikipedia.org/wiki/Partnair_Flight_394 see second last paragraph under “investigation”.
When I worked for deHavilland Canada, we had a near hundred page presentation on counterfeit parts found in industry, including bolts, bearings, and other detail parts. Similarly, the Bell Helicopter Tech Rep stopped by when I worked with the Bell 206 maintenance group, and showed us counterfeit Bell parts (which were cast, rather than the required forged), and finished and marked so as to deceive the user into thinking that they were genuine.
Regular AN/MS bolts are forged (not ground, those are close tolerance aircraft bolts, and the ground shank is obvious). More key to quality is how the threads are formed, and how the bolts are heat treated.
A special, or high tensile bolt may be used in an application where the bolt is in single or double shear, and the nut is doing little more than assuring that it stays put (nut not taking any tension load).
A terrifying read about how a pin was incorrectly manufactured, and still got thorough Bell’s quality control system, can be found here:
https://www.tsb.gc.ca/eng/rapports-reports/aviation/2021/a21w0045/a21w0045.html
Notwithstanding the very sad Bell event, buy your hardware from a reputable source. Certification of the actual hardware is nice (and may be required) but trusting the source is key to assuring that the hardware will be safe for aviation use. The more critical the application, the more attention you pay to certification – as long as you understand the criticality in the first place. In some cases, the aircraft manufacturer will specify a proprietary part number for what may appear to be a standard bolt. But their proprietary bolt may have special characteristics necessary to be safe in that application – substitution unsafe! Use the bolt that the manufacturer specifies, and obtain it from a trusted source – standard hardware is not that costly….
Yes; this needs to be seen in the right context. One must not be a fool, but we are not the BBC whose job is to protect the stupid at all costs 
So we can have an adult discussion here.
For some reason Snoopy has not been back to tell us what this bolt is for, which is obviously absolutely crucial. My guess it that it is a Socata aircraft – a TB or a TBM. The locknut is nylon so it probably isn’t that critical.
For a bit of context, see this and this. Both links show dramatically overpriced metric bolts – typical of Socata and the whole European/metric system which has no standard parts (also here).
The former link discusses a bolt which is fairly critical in that it holds together the exhaust clamps, so you don’t want it to be made of absolute crap. The latter link discusses a totally noncritical bolt which could be made from hard aluminium. It is made of stainless for a) non-corrosion and b) make sure it is soft so is “sacrificial” if over-done.
In some cases, the aircraft manufacturer will specify a proprietary part number for what may appear to be a standard bolt.
Sadly this is standard practice in Europe, because it prevents bypassing the “aviation” supply channel. The ~10x uplift in selling price, and the ~25% maint co. supply margin, must be protected at all costs. It is also used to stop people walking into a shop and looking up pricing on Amazon – the mfg produces different P/Ns for the two channels 
The vast majority of Socata parts are thus obfuscated.
Sadly this is standard practice, because it prevents bypassing the “aviation” supply channel
It’s a practice by some manufacturers, particularly those aligned with less cost sensitive markets, but I don’t think it’s standard practice for hardware on most planes. More often the manufacturer’s parts catalog calls out the hardware by its standard AN/MS part description, making it available for multiple competitive sources. If that were not the case, especially in the past when many of our planes were introduced and a more intelligent mass market was in play, people would and did bypass the product.
The same might not be true for parts which are less obviously standard hardware. It’s all about what the manufacturer thinks the market will accept, and actually a pretty good metric of the manufacturer’s respect for the savvy of its buyers.
Socata do it almost universally. I can see it is not used by US manufacturers.
All common metric bolts:
Most of those linkage bolts are not ground AFAICT. The actual contact is between two brass bushes, one being a press-fit into a cast or machine aluminium component which is £1k-2k and which is not legally serviceable because there is no CMM
But this thread is about some other bolt; I suspect these just hold some minor sheet metal structure together.
Peter wrote:
But this thread is about some other bolt; I suspect these just hold some minor sheet metal structure together.
A well designed airplane will not overkill attachments by using a larger bolt for a smaller load. There are bearing factors to be considered, which means that thin sheet metal is not bolted together, unless it’s a multi layer sheet metal structure (like a Cessna wing spar). Expect to see a bolt used in a way that a noticeable amount of its capacity is being used in ultimate loading cases. In a repair, a larger bolt might be used to return a fit, but again, only to a certain point. For reasons of weight, cost, and bearing, the bolt size is probably appropriate to the ultimate loading case – as opposed to being dozens of times too strong.
