Stainless fasteners

[Chicken lights]

This might not help a lot of people out, but I learned last week that there is 18-8 stainless hardware and 316 stainless. The 316 has molybdenum in it and makes it more corrosion resistant

Chances are most places are going to sell the 18-8 grade of stainless.

I haven’t looked yet into the actual bolts or nuts, I was buying some flat washers at Spaneour and noticed they had two different listings for the same sizes.

I’ll probably start switching over to 316 as much as possible, unless someone has a better idea.

 

[PeterT]

18-8 is just a 2-parameter specification that can encompass different SS alloys. It doesn't necessarily make it inferior, but you are right - the addition of molybdenum (and other ingredients) generally make it more corrosion resistant. I was told (never corroborated) that there is actually a lot of 18-8 in everyday external service. Everything is subject to oxidization, just boils down to if thats acceptable rate for your application. Higher corrosion resistance really comes into play with salt water / marine / acid / food grade applications. For fasteners 316 might be an easy decision depending on price. But for machining, some of these common SS alloys can be a real bugger.

https://victorybolt.com/what-are-th...-18-8-type-304-and-type-316-stainless-steels/

 

[Chicken lights]

18-8 is just a 2-parameter specification that can encompass different SS alloys. It doesn't necessarily make it inferior, but you are right - the addition of molybdenum (and other ingredients) generally make it more corrosion resistant. I was told (never corroborated) that there is actually a lot of 18-8 in everyday external service. Everything is subject to oxidization, just boils down to if thats acceptable rate for your application. Higher corrosion resistance really comes into play with salt water / marine / acid / food grade applications. For fasteners 316 might be an easy decision depending on price. But for machining, some of these common SS alloys can be a real bugger.

https://victorybolt.com/what-are-th...-18-8-type-304-and-type-316-stainless-steels/

The road salt and pickle brine they put down on the roads plays havoc with anything metal attached to a vehicle.

I put those extra lights on my mud flap hangers around Christmas and the hardware is rusty already. It WAS all stainless at the time. Then the rust starts to stain the stainless brackets.

I didn’t notice much price difference between the two materials

As always, you’re a fountain of information, sir

 

[Chicken lights]

As a bit of an update as I keep learning-

Metric bolts/hardware typically comes in A2 grade stainless. A4 is available, much like 316 is an upgrade over 18-8

According to the bolt store, any grade stainless bolt is going to be between a grade 2 and grade 5 bolt, as a strength comparison. They said generally if you’re using stainless you’re not necessarily worried about strength. Which I tend to agree with.

 

[Chicken lights]

So why does stainless bolts and nuts sometimes gall and not want to come apart? Sometimes the nut won’t turn and the bolt ends up breaking
Usually not a big deal but I’m curious if one of you guys has an answer

 

[Dabbler]

Stainless needs a copper anti-seize to prevent galling. This even happens with custom-made-hardened 440 stainless fasteners. The nickle and zinc anti-seize just don't cut it as well. (sometimes the copper stuff is billed as 'for stainless')

-- You can get away without it. but one day, it will gall, and at the most inconvenient time.

 

[Chicken lights]

Stainless needs a copper anti-seize to prevent galling. This even happens with custom-made-hardened 440 stainless fasteners. The nickle and zinc anti-seize just don't cut it as well. (sometimes the copper stuff is billed as 'for stainless')

-- You can get away without it. but one day, it will gall, and at the most inconvenient time.

Interesting.
I do generally use copper antiseize on everything. There might be one silver antiseize kicking around that I might have to donate somewhere.

Another frustrating thing is when people use stainless bolts but regular grade 5 nuts, which rust and seize on there.

It’s kind of funny, on my big truck when I work on stuff I can tell where I’ve been because stuff comes apart easily yet what I haven’t touched is a ball of rust and fights tooth and nail to come apart

 

[Dabbler]

... I forgot about the silver anti-seize... What I use on grade 8 steel bolts/nuts. (!!)

 

[Chicken lights]

... I forgot about the silver anti-seize... What I use on grade 8 steel bolts/nuts. (!!)

Why would you use a different anti-seize on grade 8 bolts versus stainless?

I’ve never actually looked into why they have different anti-seize, for some reason I thought it had to do with heat. Grey/nickel/silver was low temp and copper was high temp?
I know what I’ll be reading up on this weekend

 

[PeterT]

I found some general information like this when I inadvertently ordered silver anti-seize. Turns out silver also contains copper, didn't know that. As well as graphite & other ingredients at different proportions. They mentioned silver is good for finer threads which is probably better for my purposes. These products help with aluminum on aluminum which I encounter occasionally & can be a bugger.
https://www.all-spec.com/loctite-anti-seize
https://www.crcindustries.com/world-anti-seize/

 

[Chicken lights]

I did not know there was that much to know about antiseize. Fascinating

 

[Perry]

Just to add to the conversation. You have to be careful with mixing different anti-seize compounds in high heat applications. The anti seize mix can turn into an epoxy (for lack of better term) and you may never get the item out.

The change of a brand of anti seize compound and the lack of "cleaning the old type of compound off" caused a number of unscheduled aircraft engine changes because we were unable to remove the igniter plugs. Expensive lesson.

 

[Dabbler]

I have a big bottle of Silver that was given to me. The tiny bottle of copper cost me a small fortune (the days before Internet comparison shopping) because I needed it that morning. So I use up the silver on everything non-stainless and save the copper for the stainless.

I use anti-seize on steel bolts that will see weather and heat. I just grease in normal occasional weather, and nothing on indoor grd 8 bolts. I try to never use grd 5 or less for anything, excelt to use grd 5 nuts on occasion where they won't be stressed if cost is important, like on my gantry crane.

 

[Chicken lights]

I have a big bottle of Silver that was given to me. The tiny bottle of copper cost me a small fortune (the days before Internet comparison shopping) because I needed it that morning. So I use up the silver on everything non-stainless and save the copper for the stainless.

I use anti-seize on steel bolts that will see weather and heat. I just grease in normal occasional weather, and nothing on indoor grd 8 bolts. I try to never use grd 5 or less for anything, excelt to use grd 5 nuts on occasion where they won't be stressed if cost is important, like on my gantry crane.

I gave up on grade 5 hardware a couple years ago. I’ll use it in a pinch but I haven’t bought or stocked any for awhile now.

There’s a Fastenal close to me, I priced out a bunch of 1/4” and 5/16” grade 8 hardware. It was around $40 for 500 pieces, crazy cheap. I took that quote to a local bolt place I prefer dealing with, they said they couldn’t touch that pricing, I paid about $40 for 250 pieces. I was skeptical on the quality from Fastenal for the price quoted, but they may have been ok

I don’t actually know what the difference is between a grade 5 1/4 NC and a grade 8 1/4” NC, I just know a grade 8 or a stainless bolt has a greater chance of coming apart later. Especially with antiseize on there.