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When I built my CMC I decided to use stainless steel nuts and bolts.

I pretty much ignored the warning at the hardware saying to use anti-seize.

Galling can happen causing the nut to seize on the bolt. 

I just had to cut off one of my front seat mounting bolts and yesterday spent about 8 hours getting a nut off one of my rear seat mounting bolts.

Earlier I had to cut off one of the front body mount bolts on top of the front torsion tubes.

1957 CMC (Speedster) in Ann Arbor, MI

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Mike,

I feel your pain and have made the same mistake in the past.  Anti-seize will definitely help, however I typically use a zinc plated Nyloc nut on stainless bolts.  A major concern with stainless is the strength of the fastener.  Many commercial stainless steel fasteners are very soft and will twist off or shear easily.  For this reason I do not use stainless fasteners in highly stressed applications.  However, I do use stainless in a lot of places because of appearance and corrosion resistance. 

Also, you can polish stainless to where it looks almost like chrome! 

James

Like James, I use stainless hardware where it makes sense... but never when it REALLY matters in terms of strength.

We tend to overdo it on the corrosion resistant hardware, in an effort to do it "nice". Very, very few of us use these cars in a way that they will ever see inclement weather, and the average Grade 8 fastener could probably stay submersed in water for a year before it started corroding. I only wash mine about 1x/yr. The rest of the time I use a waterless cleaner (Captain Richard's Best, or the like).

Stan Galat posted:

Like James, I use stainless hardware where it makes sense... but never when it REALLY matters in terms of strength.

 

So Stan....stainless for corrosion resistance but not strength ? Wow. I always thought stainless was more or less for both but I'm sure no nut and bolt expert by far.  Is it that stainless is hard but not strong or something ? I've tried to drill through it and it can be a bugger so I probably assumed that it meant ss hardware is strong. Thanks...

@David Stroud IM Roadster D

Because of the alloying elements which give stainless steel is corrosion resistance, it is not as strong as many steels.  Stainless has a lower carbon content and is similar in strength to a grade 2 fastener.  Grade 5 and 8 fasteners are a higher carbon, heat treated steel that give you much better mechanical properties.  

Also, the chromium in stainless steel makes it work harden easily.  This is why it is so difficult to machine or drill.  Stainless has the odd properties of being “tough” but not very strong.  The alloying elements also cause stainless to be “sticky”, thus causing the galling problem.  Stainless steel tends to “stick” to itself easily.  

James

Having worked with a lot of stainless fasteners, my past experience tells me that when you install the nut and it doesn't go on smoothly through the nut...stop right there. you probably have a misfit on either the bolt or the nut and galling to the point of twisting off the bolt will occur. That's in either direction at that point. Find out which part is defective...nut or bolt and replace and discard the offender. Stainless is not a strong fastener so consider that as others on here have said. That's keeping in mind that we tend to over do it in the application of fasteners...Really think about what your application is.............Bruce

Yeah, suspension, seat belts,engine/trans mounts, and steering I use grade 8. 

Bolting an oil cooler to the frame? SS. I have lots of SS 1/4-20 and 10-32 fasteners. Luckily, my grandfather worked at a SS fabrication shop in the 60s. I have coffee cans full of various lengths and threads, all in stainless. So a fair amount has made it into the car.......

I guess we've all learned a LOT from this thread - thanks to all who've added to it.

James wrote: "Stainless has the odd properties of being “tough” but not very strong."

I can vouch for that.  I made a couple of driving light mounts out of 1/4" thick SS - MAN!  That stuff is a B---- to work!  Even heated the BeJezus out of it with a torch and it was STILL hard to work!   Same thing with drilling it - really tough.  

I grew to think of stainless steel bolts as almost brittle - stress them a bit with shear and they break much earlier than regular steel.   I was not at all aware of the galling part so now I'm gonna rethink what gets installed where.

Thanks, everyone!

 

A little word of caution about never seize and anti seize...never use it when your using a torque wrench and tightening to a specific value. You may twist off your fastener before you reach your torque value. Always us the lubricant called for for the fastener. Sometimes they state No lubricant or dry. Wheel lug nuts are a common abuse of never seize......be careful.............Bruce 

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