Looking for bolts

[thinger2]

Do not attempt to recut a thread with a different die. That is an incredibly dangerous thing to do.
When you run a die with a different "pitch" over an existing thread it cuts through that thread at a shallow angle and now, instead of a continious thread from top to bottom, you have a thread cut into segments from top to bottom and the only part that holds is that shallow angle cut.
Plus, like Schurkey said, cut threads are much different than rolled threads.
Get yourself a thread pitch gauge.
They come in standard (sae) and metric.
An SAE thread gauge will not fit on any metric bolt
A metric will not fit on any SAE bolt.
The thread gauge will fit exactly to the thread space on the bolt in question
No gaps
Once you find the proper gauge fit, you know if its a standard bolt or a metric and you know the pitch.
Now, you need to know the "major basic diameter" of the bolt
The outside dimension of the threads
In this case .306
So, because of tolerence and cheap ass bolt at .306 it could be a M8x1.25
But it isnt
It is a 5/16-18 because a metric thread gauge would not fit but the SAE 18 thread fits perfectly
The next part of the puzzle is a thread chart
Most hardware suppliers have pocket reference books for a couple of bucks that will show commonly available thread sizes.
There are online calculators that will convert decimal to fraction but they are mainly useless.
It doesnt help to know that your decimal converts to 122/177
You just need a bolt.

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[Schurkey]

To determine SAE/Metric, I'd be looking first at the head markings.

 

[thinger2]

To determine SAE/Metric, I'd be looking first at the head markings.

That is another very good idea.
I think the entire subject of bolts and clearences and tolerences could save people from a lot of mistakes.
And I think the best contribution would involve types of bolts and grades of bolts.
When to use galvanized?
Never
When to use Stainless?
Never
I think that would be a good conversation to have and I think we should do it

 

[454cid]

When to use galvanized?
Never
When to use Stainless?
Never

Really? Stainless, I've heard the stuff commonly availble simply isn't strong enough for most automotive use, although, I would think better grades exist from places like McMaster..... I've never checked, Though.

Why not galvanized? This is the first time I've seen that one mentioned as a bad idea, but it's not something I normally hear suggested either. I suppose it's not a Grade 8 or 10.9 equivalent, but is there more? Recently, on another forum someone suggested galvanized, I think because many OEM bolts have a similar color.

 

[thinger2]

Lots of people misunderstand the properties of stainless.
They have this notion that it is better because it costs more.
Stainless is actually much softer and more brittle than even a grade 5 bolt and it galls up the threads bad.
Stainless also can deteriorate rapidly in certain conditions.
It is available in many types but rarely of any use in a vehicle.
Galvanized bolts are "hot dipped" cheap low grade bolts found at home depot.
Great for building a fence, not for building a car.
Zinc plated bolts are not the same as galvanized bolts.
Zinc chromate bolts are not the same either
Nor is yellow chem film and about 25 other flavors.
It really is worth the effort to take a dive into bolts and threads and plating and bolt hardness and shear strength etc..
Its a bit of arcane deep in the weeds stuff but,
That knowledge not only can keep you from having to fight a broken bolt, that knowledge can also keep you from having a lower control arm or maybe a ball joint or tie rod break on the freeway because you put the wrong hardware on it.
Ive been through a broken ball joint and a broken tie rod end while driving

You do not want to go through what I went through on either occassion.
It really really sucked

 

[Hipster]

Never stainless, especially not into aluminum threads. Along with the galling there seems to be corrosion that takes place between the dis-similar materials with stainless(electrolysis?). Brittle, lack of tensile strength, check those boxes, the bolt heads like to detach before the threads back out leaving you with a piece of seized stainless all thread to drill out. Are we having fun yet?

Polished stainless fasteners were really popular in the 90's with the motorcycle crowd. It resulted in many trashed castings.

Chrome fasteners, not that what's need here can be subject to hydrogen embrittlement that reduces the strength if you're not picky where it comes from. Gardner-Wescott is about the only name I trust if you need pretty.

Ditto, on the thread cutting, cut threads don't have the same strength as rolled and rethreading a fastener of one size to another is a really bad idea.

 

[Hipster]

That is another very good idea.
I think the entire subject of bolts and clearences and tolerences could save people from a lot of mistakes.
And I think the best contribution would involve types of bolts and grades of bolts.
When to use galvanized?
Never
When to use Stainless?
Never
I think that would be a good conversation to have and I think we should do it

Yes, It would be a good idea, and make it a sticky or in a general knowledge type of area.

I know in the past both Schurkey and I have been in threads discussing fasteners and torque specs etc.

 

[Schurkey]

I know of FIVE paperback books that deal with vehicle fasteners. Any one of them would be worth reading. I have all five.

The BEST one was authored by Carroll Smith (RIP). If you're only buying one "hardware" book, make it this one. Anything he wrote is worth reading.--Prepare to Win, Tune to Win, Drive to Win, Engineer to Win, etc.
https://www.amazon.com/Nuts-Bolts-Fasteners-Plumbing-Handbook/dp/B001OXCTSI/ref=sr_1_3?crid=3IMFYFOUU3J5V&dchild=1&keywords=carroll+smith+nuts+bolts+fasteners&qid=1606645053&sprefix=carrol+smith+nuts,aps,218&sr=8-3

Mike Mavrigian wrote a similar book.
https://www.amazon.com/High-Perform...an+nuts+bolts+fasteners&qid=1606645168&sr=8-2

As did Timothy Remus
https://www.amazon.com/Hot-Rod-Hard...olts+fasteners&qid=1606645244&s=books&sr=1-24

and Forbes Aird
https://www.amazon.com/High-Perform...ds=Forbes+Aird+hardware&qid=1606645436&sr=8-1

Then there's good ol' John Deere, the least-useful of the five books:
https://www.amazon.com/Fasteners-Fu...Deere+fasteners&qid=1606645515&s=books&sr=1-2

 

[Pinger]

Remember though, that bolts can be viewed differently if in tension as a 'fastener' (eg cylinder head bolt) or in shear (eg, suspension bush).
The latter are much less fussy about threads - the threads often enough don't have to do much more than stop the bolt from going missing.

 

[PlayingWithTBI]

Stainless is actually much softer and more brittle than even a grade 5 bolt and it galls up the threads bad.

Not necessarily, cheap ass Fastenal SS bolts do because they use the same soft alloy for their bolts and nuts. Try Lawson SS fasteners sometime, they're closer to Grade 8 and have a different alloys so they don't gall so easy. But they aren't inexpensive. In food plants we used nothing but SS fasteners.