Nuts About Fasteners

Story by Bill Holland

Our cars are held together with a dizzying array of fasteners– all sorts of nuts and bolts, studs and washers. They may not be as captivating as the components they attach to one another, but don’t take them for granted. A chain is only as strong as its weakest link, and faulty fasteners have the power …

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Neat info!

Now I feel like I need to rebuild my engine just so it has proper fasteners....

This is nothing but a commercial for ARP. Many mistakes or misrepresentations are present.

Chas_H wrote: This is nothing but a commercial for ARP. Many mistakes or misrepresentations are present.

Ok so correct them. Seriously!!! Just saying some one is wrong does not help. Bring the tech. Wright a follow up article with facts citing sources so we can all learn somthing.

@The OP. That article has a ton of info in it. Thanks for putting that together. I am going to have to read that several times and book mark it for future reference.

In reply to dean1484:

OK, I'll start with the claim head gaskets are located by the head fasteners. That might be the case with a very few engines, but most engines have dowels to locate both the head and the head gasket.

But I'm gonna stop there. I'm not a maker of fasteners or a publisher of a magazine. If someone wants to pay for my expertise they can step forward.

In reply to Chas_H :

Although much of the information is trivial for anyone familiar with fastener engineering (a common issue I run into as an engineer:the overwhelming majority of technical articles are written for the lay person and fall under "stuff I pretty much already know"), I would disagree that the information is incorrect. Some things may be a bit overstated, but I would not say is either misleading or incorrect. The lube, tighten bolts, remove, clean, then loctite and tighten procedure they mention is probably well into the realm of diminishing returns, but still technically correct and applicable.

In reply to BA5:

I never claimed it was all incorrect.

Well.... I wouldn't say any of its incorrect. That's at least what I meant.

In reply to BA5: Are you claiming that head gaskets are indeed located by the fasteners, and a switch to studs from bolts will locate them better, as the article does? A technical article should not include overstatements or product hype; this article is basically ad copy.

Studs don't "give" any more than bolts of equal cross section. Changing thread pitch changes the load on a fastener if the tightening torque remains the same. In the case of your Volvo, it sounds more like a head gasket or engine temperature issue, rather than one of fasteners. I've done a lot of work on Volvos in the past and never had an issue with fasteners or head gaskets. I'm not knocking replacing bolts with studs. It was the suggestion that studs would locate a gasket better than bolts, and that is just not so.

Actually I think the point made was that head assembly is easier when using studs as they act as a guide to slip the gaskets over. There is no lining up required.

Didn't see too much misinformation really. And if you wanted to talk to fastener experts in order to gain material for a story, where would one go if not ARP? Seems as good a source as any. And most likely cheaper than you.

Chas_H wrote: In reply to dean1484: OK, I'll start with the claim head gaskets are located by the head fasteners. That might be the case with a very few engines, but most engines have dowels to locate both the head and the head gasket. But I'm gonna stop there. I'm not a maker of fasteners or a publisher of a magazine. If someone wants to pay for my expertise they can step forward.

In reply to bearmtnmartin:

I'm gonna guess you never changed a head gasket on an engine with studs, or ever. There is no trick to placing a head gasket down on a set of dowels. So far my advice has been free; how is anyone is gonna be cheaper? Why don't you stick to a subject you actually understand or know something about?

In reply to Chas_H :

So, your "advice" is limited to one item, head gasket intallation, and is "free". But you cite other "misrepresentations" with no identification of them and wish to charge for your "expertise".

I say, put up or shut up.

Good info. I always enjoy these types of articles. 
 

ARP has a very good reputation in this area. I would certainly trust their advice over random internet posters. Does it promote their brand? Sure. Having some skepticism is healthy. Even better if it leads one to learn more on the topic. 
 

I have this book on the shelf in my garage. Way more detail than I will ever need. Still an interesting / nerdy read. 
 

A couple of nits to pick, and a few bits of advice:

The “Coarse or Fine Thread” section states that the larger minor thread diameter of a fine thread fastener provides better shear strength. Actually, it provides better tensile strength.  Fasteners loaded in shear must put the shear plane in the grip section of the bolt to maximize shear strength.

High strength bolts like the one shown in section 5 have a corner radius under the head for improved fatigue strength.  A standard washer under the head of such a bolt will bear on that radius and defeat its benefit.  Chamfered washers are made to accommodate the corner radius, but of course the chamfer needs to be installed on the head side of the bolt for it to work.

A general comment about stainless steel hardware (particularly the garden variety 18-8 stainless stuff) is that it prone to galling, especially when both nut and bolt are stainless.  Installing any stainless hardware without anti-seize, and particularly installing it with a powered driver risks seizing it.  18-8 stainless steel fasteners are seldom worth the trouble in any location you expect to ever disassemble again.  High strength stainless hardware will be less susceptible.

Replace any machine screw with a bruised "slot".  These things only get worse with time and removing screws with stripped heads under time pressure is usually avoidable torture.

Use Torque-Seal or equivalent to identify fasteners that have been torqued to spec (and ones that have moved).  This makes doing nut and bolt inspection much easier.

Get the book of words (shop manual).  Make fastener torque checklists for important projects.  Use a torque wrench on every critical fastener that has a specified torque, if it is accessible to one.  Using a torque wrench is a mark of professionalism.

All those little fasteners on your metric vehicle, that start out gold and pretty, eventually get rusty and look terrible.  OEM replacements are expensive.  After market equivalents from places like Bel-Metric are not.  Buy an assortment of the common stuff and use it to replace the crappy stuff any chance you get.

I'm going to go research why heat treating before forming threads produces a stronger fastner than heat treating with the threads already formed.   Hmmmm... 

In reply to Shaun :

That's the case because you're effectively forging the threads in to the material.  A heat treat will "reset" the grain structure, but for strong threads, you want the grains aligned with the shape of the thread.

This is also why formed (rolled) threads are stronger than cut threads.

For the record, mechanical engineering design 1 was the most irritating class I ever took.  I was trapped in a room discussing the technical aspects of fasteners with lots of people that didn't know the difference between the open and box end of a combination wrench.   I just needed to say that to someone that might understand or be able to relate. 

Matthew Kennedy said:

In reply to Shaun :

That's the case because you're effectively forging the threads in to the material.  A heat treat will "reset" the grain structure, but for strong threads, you want the grains aligned with the shape of the thread.

This is also why formed (rolled) threads are stronger than cut threads.

I get the formed vs cut difference, that is why I typed 'formed threads' 2X in my post.  What I don't understand yet, (and I only read 15 minutes worth of stuff so far so I'm not done and did not find an answer, Is why " heat treating before forming threads produces a stronger fastner than heat treating with the threads already formed".  I would think the stress relief of heat treating post thread forming would make for a 'stronger' thread.  But apparently somehow the gigantor forces required for forming threads into already hardened material make the material 'stronger'.  It is likely a carefully controlled several step forming process- but I'm just guessing.  I'd like to know more about the manufacturing methodology and material science/physics involved. 

AnthonyGS (Forum Supporter) said:

For the record, mechanical engineering design 1 was the most irritating class I ever took.  I was trapped in a room discussing the technical aspects of fasteners with lots of people that didn't know the difference between the open and box end of a combination wrench.   I just needed to say that to someone that might understand or be able to relate. 

 

I feel ya.  I had a design/build class with a couple of guys that didn't understand that things don't fall faster because they're heavier.  And *literally* did not know how to hammer in a nail.

BA5 said:

AnthonyGS (Forum Supporter) said:

For the record, mechanical engineering design 1 was the most irritating class I ever took.  I was trapped in a room discussing the technical aspects of fasteners with lots of people that didn't know the difference between the open and box end of a combination wrench.   I just needed to say that to someone that might understand or be able to relate. 

 

I feel ya.  I had a design/build class with a couple of guys that didn't understand that things don't fall faster because they're heavier.  And *literally* did not know how to hammer in a nail.

Sometimes life is painful.  Lloyd the machinist used to tell us college kids (he was a real machinist working in the labs at the University), that the garage is what made America so great.  Ford, Firestone, Edison, and the Wright Brothers all started in their garage.  An engineering education is good, but an engineering education with a lot of garage time is better in almost all cases. 

AnthonyGS (Forum Supporter) said:

the garage is what made America so great.  

I fully believe this.  I've gotten to travel the world and learned that people are pretty cool everywhere, but folks in the USA's DIY game is definitely a step above what I've seen elsewhere in the world.

In today's world I understand being skeptical, but I have been building engines (my own) for more than 45 years, and have been using ARP racing rod bolts all this time. I found them to be the cheapest insurance you can buy. Now I'm building Rover V8s and Hondas, (aluminum blocks) so I use the head and main studs too.