Originally Posted by corvettecrazy
I want you to look at this picture and tell me which bolt you would rather have holding your suspension together.
I would chose a high quality bolt.
First you displayed two different bolts.
The new one is NC, (National coarse) while the rusted one is NF (National fine).
If both bolts were new the one on the right(rusty) is the stronger of the two.
See chart on second link, simply as it doesn't have the cadmium coating,
and it has the NF thread.
What do you define as a "high quality bolt" ?? ??
I did not say that an old rusted bolt was as good as a new bolt.
I said that" if it does the job, it does the job."
An old corroded bolt will not be capable of "DOING THE JOB" and
therefore, is excluded from the conversatuion.
There is no way to tell the quality of that rusted bolt.
It may have been a "factory spec" bolt when it was new.
The quality of the bolt has nothing to do with this topic.
We are simply speaking in terms of grade.
Grade is the tensil strength of a bolt, often determined by heat treatment, and/or chemical makeup, to fit a specific enviornment.
( i.e. high /low Carbon steel, silicon steel, and others. )
This is not Quality.
Quality is.... the dimensions, thread pitch, and strengths, staying within specific limits when stressed,
which all bolts will do. grade 3 .... or grade 8.
the following, excerpted from the above link.
What are the basic differences between an SAE Grade 5 bolt in accordance with SAE J429
and a high strength structural bolt?
While both bolts have a minimum tensile strength of 120,000 psi,
the differences include the following:
Controlled grip ranges min/max for each diameter/length combination of A325'*
A325'* only available in heavy hex configuration as defined in ASME B18.2.1
A325'* have specific quality assurance requirements
A325T is for lengths 4D threaded fully
How is shear strength of fasteners determined? Why don't industry fastener standards include such values?
Common practice for steel fasteners is to assume shear strength will approximate 60% of minimum tensile strength. Published data in commercial (non-aerospace fields) does not offer much guidance on shear strengths for bolts, screws, or studs. The first reason is that the number of components loaded in shear is considerably less than for tension, compression, bending, or torsion. The primary reason, however, is the difficulty in obtaining accurate test data. Shear testing inherently involves a number of variables. Therefore, tests are less reproducible than testing for such properties as tensile or yield strength. Most shear testing has been by arbitrary procedures that provide empirical results. The greatest need for shear test data is in structures that are riveted, pinned, or bolted, and also where service stresses are actually in shear. Notable examples are found in the aerospace industry. (A recommended shear test method is given in ASTM B565.) "
Now argue, why an Aircraft bolt is better....
Or how you can tell the difference between one or another.
Case, now closed.
I seldom go to a shootout unarmed....