Hi gang. I've just ordered some stainless steel bolts for my Bronco, and wondered what strength they are. The stainless is "18-8", if I remember correctly. I know it's not equal to grade 8, maybe grade 5?
Thanks,
TLR
Thanks,
TLR
How strong are stainless steel fasteners?
- Thread starter TheLoneRanger
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18-8 is not a strength grade but refers to 300 series steel (18% chrome, 8% nickel).
The lowest grade fastener I'd use in an automotive application is 8.8, which is quenched and tempered alloy steel. Stainless steel may not be strong enough in some applications and threads may be prone to galling.
The lowest grade fastener I'd use in an automotive application is 8.8, which is quenched and tempered alloy steel. Stainless steel may not be strong enough in some applications and threads may be prone to galling.
Thanks for the reply, Mori. Good to know about the 18-8.
These are all exterior fasteners, for use where they're exposed to the elements. Mirrors, lighting, rocker panel moldings and such.....
These are all exterior fasteners, for use where they're exposed to the elements. Mirrors, lighting, rocker panel moldings and such.....
Is it safe to use stainless steel fasteners on the various vehicle metals/alloys in regards to galvanic corrosion?
Anyone know?
Here is one galvanic series chart:
http://www.corrosion-doctors.org/Definitions/galvanic-series.htm
Anyone know?
Here is one galvanic series chart:
http://www.corrosion-doctors.org/Definitions/galvanic-series.htm
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Holy Smokes! I didn't know Mori knew about fasteners.
18-8 Stainless Steel is a generic designation that includes types 301, 302, 303, 304, and 305.
It's pretty weak stuff, it's about 75,000 lb/in^2 tensile strength which makes it roughly an SAE Grade 2, significantly weaker than a Grade 5.
The 8.8 Mori refered to is a DIN clasification that is approximately equal to an SAE Grade 5 in mechanical properties.
It's pretty weak stuff, it's about 75,000 lb/in^2 tensile strength which makes it roughly an SAE Grade 2, significantly weaker than a Grade 5.
The 8.8 Mori refered to is a DIN clasification that is approximately equal to an SAE Grade 5 in mechanical properties.
Stainless steel is non-reactive electrically; so yes, you can use them on all applications without worrying about electrolytic corrosion. Never mix aluminium fasteners with steel fasteners though.
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It's not only DIN, it's ISO. I don't do SAE (if I can avoid it).
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Quote:
Holy Smokes! I didn't know Mori knew about fasteners.
Only enough to get by.
Kestas
Staff member
Stainless steel will produce a galvanic reaction with steel, but it's the opposite of aluminum. Mild steel will sacrifice itself to protect the ss in the presence of an electrolyte. The ss will not corrode.
'Stainless' steel is highly alloyed, where everything else being equal will be more brittle/less 'strong' at a given hardness level than a decent carbon or tool steel. Stainless is nice provided it is designed for the loads and cost isn't a concern. As others have noted first look at the grade of fastener required for the application.
Some of the stainless steels harden nicely, different alloys are used in tools, knives, bearings, etc., but they can also be expensive. It might have changed but at one time the 'holy grail' of aircraft landing gear was a stainless that was strong as some of the (non-stainless) alloy steels, as it would also be less prone to corrosion.
Some of the stainless steels harden nicely, different alloys are used in tools, knives, bearings, etc., but they can also be expensive. It might have changed but at one time the 'holy grail' of aircraft landing gear was a stainless that was strong as some of the (non-stainless) alloy steels, as it would also be less prone to corrosion.
Until you get into specialty SS fasteners that are deigned for high strength, all you get is 300 series stuff that's the equivalent of an SAE grade 2 fastener.
It's not wise to use it in an application that needs a Grade 5 or higher.
It's not wise to use it in an application that needs a Grade 5 or higher.
They will be stronger down the road for sure, when conventional steel fasteners have rusted and lost strength.
Might as well go titanium...
If you want strong stainless fasteners, check out ARP. Their stainless is stronger than grade 8.
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