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Old 07-12-2019, 09:01 PM   #1
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Possible problem with Elevator bolts

I'm involved with rebuilding a 92 Excella. I did a shell off and I'm now preparing to install new channel to the frame. I decided to use 3" stainless steel hex head tap bolts with stainless flat washers and stainless nylon centered lock nuts. I've decided to dry fit the new channel and make sure the shell will fit over it okay before I cut and install the flooring. I installed the first tap bolt then I broke the second bolt during installation. Now, I'm wondering if stainless steel is a good idea since it is rather soft. I'd love some advice and or encouragement. I'm happy to buy new bolts, washers and nuts if that's what is needed, I just want this to be right.
Also, has anyone else used lock nuts for this purpose and is installing and removing them okay or does that make them less effective?
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Old 07-12-2019, 09:18 PM   #2
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Yes, stainless is soft. You could always use nylon or stainless washers with steel bolts. I have done that on various projects to reduce galvanic interference where touching aluminum. I dont see an issue with nyloc nuts.
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Old 07-12-2019, 09:36 PM   #3
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Originally Posted by dznf0g View Post
Yes, stainless is soft. You could always use nylon or stainless washers with steel bolts. I have done that on various projects to reduce galvanic interference where touching aluminum. I dont see an issue with nyloc nuts.
Good thought. Stainless bolts were not my first choice, but then I may have over thought it, remembering how rusty most of 26 years old elevator bolts were. Then I thought about all of the stainless screws and bolts that are used on sailboats and the like and they get a lot of stress and I decided to give stainless a try. When the second bolt broke from twisting on that nylock nut it made me question how well these bolts would hold up bouncing down the road. The thought of them shearing in half scares me. Even rusty the original ones were still in one piece.
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Old 07-13-2019, 07:00 AM   #4
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Believe it or not, the galvanic interaction between stainless and aluminum is many times higher than it is with regular steel.
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Old 07-13-2019, 07:12 AM   #5
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I did not know that.
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Old 07-13-2019, 08:05 AM   #6
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As may be apparent I don't know much of anything about steel. Here I am ready to begin bolting down my channel and I discover that I bought the wrong type of steel bolts.

In my case these bolts are fastening the channel to the outriggers and frame perimeter. Instead of using the round wafer headed elevator bolts I'm using hex head full thread bolts unless I find some partial thread bolts that will do the trick. Since I'm using nylon insert lock nuts I'm thinking that bending over the remaining bolt stem is not necessary and if that is true then neither do they need to be 3" long. How does that jive with conventional wisdom?

Are Grade 8 bolts acceptable?

If not what type of steel is recommended?

Regardless of the bolts I end up using is it wise to use the Stainless flat washers and Stainless Nylock Nuts I already have?

I'm open and ready to receive your shares.
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Old 07-13-2019, 09:28 AM   #7
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I like the idea of using stainless bolts, although, you still have a steel frame, and there can still be rust....Unlike the boat you referenced, where virtually no steel is found at all.....

Perhaps there is a higher grade of stainless bolt available at your source?
...in either case, I like your idea, even if you cannot make it work. Seems odd that threading a nut onto those bolts is stressing them out that much.
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Old 07-13-2019, 09:38 AM   #8
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I use stainless steel bolts whenever possible in camper renovations. Occasionally I've had problems with galling that has resulted in broken bolts. This may be the problem you're facing. I don't think the difference in the strength of a bolt (SS vs various grades of steel bolts) is going to matter in attaching the shell to the frame.
There is information on Thread Galling here.
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Old 07-13-2019, 09:56 AM   #9
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Quote:
Originally Posted by Re-Pete View Post
I'm involved with rebuilding a 92 Excella. I did a shell off and I'm now preparing to install new channel to the frame. I decided to use 3" stainless steel hex head tap bolts with stainless flat washers and stainless nylon centered lock nuts. I've decided to dry fit the new channel and make sure the shell will fit over it okay before I cut and install the flooring. I installed the first tap bolt then I broke the second bolt during installation. Now, I'm wondering if stainless steel is a good idea since it is rather soft. I'd love some advice and or encouragement. I'm happy to buy new bolts, washers and nuts if that's what is needed, I just want this to be right.
Also, has anyone else used lock nuts for this purpose and is installing and removing them okay or does that make them less effective?
I do not claim to understand anything about the various qualities of stell and bolts. When I have bolt problems I visit a Fastenal store and get excellent advice for the most exotic solutions in SAE DIN ISO standards - just as I need it per case to be solved.
I am not getting paid for referencing them but I can tell you that they were always helpful!
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Old 07-13-2019, 10:59 AM   #10
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Stainless is brittle and the threads gall easy. Always use anti-seize, and you can buy higher quality stainless fasteners than those typically available at big box stores.
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Old 07-13-2019, 12:25 PM   #11
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Stainless Steel

Stainless Steels comes in many varieties - it's basically a generic term for 5 classified types that are defined by the basic metal recipe (content). The recipe is the percentage of chromium. nickel, sulfur, iron, and many more elements, as well as the metallic structure itself. These types are then further classified into hundreds of different grades. These have been developed over many years to satisfy different requirements - corrosion resistance, strength, weldability, formability, etc. Consequently it's not wise to base a design decision solely on the term, Stainless Steel. Many stainless steel grades are soft, and in fact are often quite weak compared to steel. Most stainless grades do not harden well, as steel does, and this leads to many other issues compared to steel. Galvanic reaction also varies based on type. The most common stainless grade fastener normally available at hardware stores is type 18-8 - a low cost, weak and soft grade. It has decent corrosion resistance, but is much poorer than another semi common grade, 316. A 316 bolt will cost 3 times what the same size 18-8 bolt does.

If I were doing the job you are, I would see about exchanging the stainless steel fasteners for good old grade 5 steel bolts, nuts and washers. These will do the trick strength wise and last for a long time. (Grade 5 bolts have 3 radial lines on the head.) I wouldn't use the more common and cheaper grade 2 bolts - these have 35% less strength of a grade 5 bolt. Tensile yield strength of 57,000 psi vs. 92,000 psi. I think grade 8 is overkill but better yet if you want to pay for it. For comparison Stainless 18-8 bolts yield strength is 20,000 to 65,000 depending on exact composition.

Precoating the parts prior to assembly, and then recoating after assembly with a good primer and paint will help as well. Not sure if this helps, but I guess my bottom line suggestion is to do some fastener research or talk to a true professional before you embark on a very difficult project.
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Old 07-13-2019, 12:51 PM   #12
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For an outside the Airstream advice, check with Shelby Cobra (Carroll Shelby origin). They have Aluminum shells on their frames. I am sure they would be happy to tell you what kind of hardware they use. There are all kinds of hardened steel bolts used from boats to airplanes.

Shelby American, Inc. Las Vegas, Nevada (Great tour as well!)
aka: Carroll Shelby Museum and Factory Tours in Las Vegas

I like the polished aluminum... maybe, some day.
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Old 07-13-2019, 01:56 PM   #13
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What Can I Do to Prevent Galling?
Slow Down Installation Speed
Because heat generated by friction is a contributing factor in galling, slowing down the installation speed can prevent galling. It is recommended that power tools not be used for the installation of stainless steel or other fasteners prone to galling. This is especially important when using nylon insert lock nuts as these nuts significantly increase the chance of galling.
https://www.boltdepot.com/fastener-i...d-galling.aspx

THX for the discussion and learning!
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Old 07-13-2019, 10:00 PM   #14
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Quote:
Originally Posted by DavidsonOverlander View Post
I use stainless steel bolts whenever possible in camper renovations. Occasionally I've had problems with galling that has resulted in broken bolts. This may be the problem you're facing. I don't think the difference in the strength of a bolt (SS vs various grades of steel bolts) is going to matter in attaching the shell to the frame.
There is information on Thread Galling here.

Grant, Sincere thanks! Damn! That Galling information was very enlightening! I know I've heard of galling before, but I had a complete misconception of what it was. This article particularly dwells on Stainless steel bolts and nylon insert lock nuts. I was installing the lock nuts with an 18V Milwaukee Fuel impact driver. I never considered the friction and heat that was generating. Respect!

Everyone who does not no what galling is or how it happens should read Grants link to the Galling article at the BoltDepot.com.
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