Any nuts and bolts experts here?

[Recoil Rob]

I'm rebuilding and modifying a 2004 Sealion boat trailer that was, and will be, used in salt water.



Seems many of the original bolts were only zinc plated and not hot dipped, they're badly rusted and I need to replace them.


Is there a source for hot dipped Grade 5 bolts or am I dreaming?


I've tried all the online trailer specialists, I can find hot dipped U Bolts but not regular hex heads. They all sell SS hardware which is about twice the price and still not graded.


Any leads?

 

[Bogie1632]

I believe boltsplus.com, boltdepot.com or Fastenal should have hex bolts that meet your needs.

V/R
Bogie

 

[Don1357]

I would go with stainless steel and call it a day. Not all stainless is the same; some are more, some are less 'stainless', but for most practical purposes they are 'stainless' enough. You can pick up the slack by religiously hosing down the trailer after every use.

 

[matt_i]

I am no expert, but:

304SS aka 18-8 is no better than a Grade 2 bolt. OK for holding your license plate on but inappropriate for structural considerations.

McMaster & Carr has ASTM A325 heavy hex bolts with a HDG = hot dipped galvanized finish starting in 1/2-13 and going up from there. Not sure what sizes you need (?)

 

[DHCrocks]

316SS would be your best bet for marine applications.

 

[brtsvg]

I’d start with McMaster-Carr. If they don’t have it it doesn’t exist. Reasonable pricing as well.

 

[Gutman]

Bolt Depot should have it.

 

[PelicanPines]

Bolt Depot delivers to me often... I'm a fan of 316SS but agree on the post mentioning Grade 2. If you need a Grade 5 structural bolt... go with hot dipped.

Best place to find the right stuff you need... a marine supply house/shop. I live in a harbor town... I am well aware of things that rust.

I paint everything with Benjamin Moore Aluminum paint... has a color and coverage similar to "antiseize"... its very thin and coats well. Just about everything metal around my house gets a coat every spring.

I used to paint my boat trailer with it. A few friends used bottom paint... but that's expensive.

 

[Wakefield]

316SS would be your best bet for marine applications.

Need to oversize the stainless in order to handle equivalent load of regular grade 5?

 

[anndel]

McMaster-Carr +1

https://www.mcmaster.com/screws/hex-head-screws/finish~hot-dipped-galvanized/

Link is for hot dipped galvanized hex bolts.

 

[tman7078]

stainless all the way

 

[TuxThePenguin]

Need to oversize the stainless in order to handle equivalent load of regular grade 5?

Yes/maybe, depending on whether it is actually using grade 5 (OP asked about grade 5, but some people just tend to default to replacing any fastener with a grade 5 or 8, even if the original was lower)

Even if it was using grade 5 then it depends on WHY they used grade 5. Did they need it to withstand a specific type of force? Or did they get a good deal on a large quantity of them?

 

[seber]

https://www.boltsplus.com/products/...+5+FINISHED+HEX+HEAD+CAP+SCREW++++BIN+#+P-7-J

 

[bpjr]

302 & 304 is common on boat trailers used in salt water here in Florida. They will show cosmetic surface rust discoloration over time but that's easily cleaned with a wire brush. They will never seize or be difficult to remove like galvanized bolts. Stronger than 316 (which stays looking new) but a lot less $$$ than 316. If you look at shear strength values, most trailers bolts are massively oversized for the application and going from grade 5 galv to any 300 series ss is structurally a non issue...even when going to the weaker 316.

I've gone from galv to 302, 304 & 316ss on boat trailers and used them in salt water for decades without problems. Changing springs and axles is way easy with ss compared to struggling with rusted galv. Otherwise, buy the cheaper hot galv bolts and replace them every couple yrs.

 

[Ralf11]

Go Titanium or Go Home

 

[Noworries]

I replaced all the "visible" trim bolts on my Harley which was about 15 bolts.. in sizes of 1/4" to 3/8" with polished grade 8 ss... this was 10 years ago and it cost ove 50 bucks then... while I am no metalurgist I do know dissimilar metals in a corrosive invironment like salt water creates issues.. dont know if that applies to stainless and mild steel tho...

 

[PZ 1]

I don't know if it would be the same in your area but check building supply places like Lowe's or Home Depot, or farm stores for hot dipped screws.
Stainless is probably just as strong as what is on the trailer now.

 

[skippydoo]

Check out ARP stainless bolts.

 

[jonshonda]

Go Titanium or Go Home

Go home

 

[Rinspeed]

I am no expert, but:

304SS aka 18-8 is no better than a Grade 2 bolt. OK for holding your license plate on but inappropriate for structural considerations.

Totally wrong.

 

[matt_i]

AISI 304 SS ultimate tensile strength = 73ksi

Grade 2 ultimate tensile strength = 60-74ksi

Grade 5 ultimate tensile strength = 105-120ksi

I could be wrong but at least I brought numbers....find on Google.

 

[TuxThePenguin]

I could be wrong but at least I brought numbers....find on Google.

A lot of times bolts are used because of availability or pricing reasons. You seem to be looking at this as "If it came with grade 5 bolts, then grade 5 bolts are 100% required, and any material with less strength will fail." But, the thing is, between the over-engineering and the fact that bolts are often bought for availability (and sometimes grade 5 are no more expensive than lower grades), means a bolt with a lower strength might be acceptable.

I don't know the answer for OP's situation. I do know there are situations when this is true, but also that there are many when it's not true ("haha go try stainless steel head bolts idiot" - obviously would be a bad idea). But there are quite a few bolts and screws you come across in life that are non-stainless steel ONLY due to cost.

But the comment you made about SS only being useful to hold on a license plate is absolutely ridiculous. That's where you lost... well, everyone. It was one of the most wrong things you could possibly have said in this thread. It is annoying to read people say stuff like that.

 

[matt_i]

A lot of times bolts are used because of availability or pricing reasons. You seem to be looking at this as "If it came with grade 5 bolts, then grade 5 bolts are 100% required, and any material with less strength will fail." But, the thing is, between the over-engineering and the fact that bolts are often bought for availability (and sometimes grade 5 are no more expensive than lower grades), means a bolt with a lower strength might be acceptable.

I don't know the answer for OP's situation. I do know there are situations when this is true, but also that there are many when it's not true ("haha go try stainless steel head bolts idiot" - obviously would be a bad idea). But there are quite a few bolts and screws you come across in life that are non-stainless steel ONLY due to cost.

But the comment you made about SS only being useful to hold on a license plate is absolutely ridiculous. That's where you lost... well, everyone. It was one of the most wrong things you could possibly have said in this thread. It is annoying to read people say stuff like that.

Ok but what else on a boat trailer are you going to hold on with SS304 or SS316 bolts in place of a Grade 5 and not-know you reduced the structural capacity? Lights? Fenders? Most everything else I can think of is structural...rollers...axle shackles...bunks if you have them...the loading winch...the trailer coupler....all come to mind as holding some decent portion of the full load.

Anyone's entitled to do their own backyard engineering and put whatever fastener, wherever they want. I wont get upset about it but I won't put my name behind it either. I took apart my 454 to TH400 transmission and found 6 different bolts with a mix of SAE and metric holding the flexplate to the torque converter, and I had pulled some reasonably heavy things with that truck. But it also doesn't make it right or long-lasting, could have easily destroyed both parts at an inopportune time. It also didn't go back together that way.

I realize people get sometimes hurt when they learn that the max-price SS fasteners aren't also max-performance in terms of basic load carrying capacity. It shocked me too but its difficult to dispute the tabulated values. I read about a person who sourced "Grade 8 Stainless Steel bolts" and knowing about the tensile strength issue, and finding zero internet hits, would need additional confirmation.

 

[Robby321]

A lot of times bolts are used because of availability or pricing reasons. You seem to be looking at this as "If it came with grade 5 bolts, then grade 5 bolts are 100% required, and any material with less strength will fail." But, the thing is, between the over-engineering and the fact that bolts are often bought for availability (and sometimes grade 5 are no more expensive than lower grades), means a bolt with a lower strength might be acceptable.

I don't know the answer for OP's situation. I do know there are situations when this is true, but also that there are many when it's not true ("haha go try stainless steel head bolts idiot" - obviously would be a bad idea). But there are quite a few bolts and screws you come across in life that are non-stainless steel ONLY due to cost.

But the comment you made about SS only being useful to hold on a license plate is absolutely ridiculous. That's where you lost... well, everyone. It was one of the most wrong things you could possibly have said in this thread.
It is annoying to read people say stuff like that.

Yep.
"Stainless steel bolts are rated for corrosion resistance. Bolt strength is rated in PSI (pounds per square inch). A stainless steel bolt has the same PSI rating as a grade 5 bolt (125,000 PSI). A grade 8 bolt has a stronger rating with a PSI of 150,000.

 

[Wakefield]

Different kinds of stainless steel have different strengths.
my Smith & Wesson six shooter is made of some kind of stainless steel (except perhaps for some of the parts of the action)
Borla advertised that their mufflers and pipes are made of different stainless than factory stainless exhaust systems.

 

[bpjr]

Ok but what else on a boat trailer are you going to hold on with SS304 or SS316 bolts in place of a Grade 5 and not-know you reduced the structural capacity? Lights? Fenders? Most everything else I can think of is structural...rollers...axle shackles...bunks if you have them...the loading winch...the trailer coupler....all come to mind as holding some decent portion of the full load.

Anyone's entitled to do their own backyard engineering and put whatever fastener, wherever they want. I wont get upset about it but I won't put my name behind it either. I took apart my 454 to TH400 transmission and found 6 different bolts with a mix of SAE and metric holding the flexplate to the torque converter, and I had pulled some reasonably heavy things with that truck. But it also doesn't make it right or long-lasting, could have easily destroyed both parts at an inopportune time. It also didn't go back together that way.

I realize people get sometimes hurt when they learn that the max-price SS fasteners aren't also max-performance in terms of basic load carrying capacity. It shocked me too but its difficult to dispute the tabulated values. I read about a person who sourced "Grade 8 Stainless Steel bolts" and knowing about the tensile strength issue, and finding zero internet hits, would need additional confirmation.

Sounds logical but charts with fastener values don't include product application...I presume you don't "realize" 9k axle leaf spring bolts are typically the same size as 1k axle leaf spring bolts. Logic says the 1k axle would have a 9x smaller bolt but it doesn't. My 3000lb boat trailer has the same size bolts as my 2500lb and 1000lb trailer.

 

[matt_i]

Sounds logical but charts with fastener values don't include product application...I presume you don't "realize" 9k axle leaf spring bolts are typically the same size as 1k axle leaf spring bolts. Logic says the 1k axle would have a 9x smaller bolt but it doesn't. My 3000lb boat trailer has the same size bolts as my 2500lb and 1000lb trailer.

I think you feel like you're contradicting my point but I think you are reinforcing what I am saying. Since the fastener sizes "dont follow logic" it says something about the design that isn't obviously visible. Something that's been determined by trials and fails by people seeking to maximize profit and minimize liability. Take that aligned with "replace a Grade 5 with a SS304" as being A-OK and my position is that its NOK.

I have 2 trailers of vastly different designs, a boat trailer of ~2000 lb axle held on with something like 3/8" fasteners and a 14k gooseneck trailer with 7k axles and is held on with somethng like 5/8" fasteners. The cross-sectional area follows something like a factor of 3.2 so that seems pretty well aligned with the generalized loads. Its very hard to compare apples-to-apples on trailer designs though....

 

[Benito]

Stainless bolts are usually on the whole weaker, as long as you understand that proceed how you wish.

 

[SeisMec]

Re: manufacturer selection of grade 5 bolts over grade 2 bolts due to price and/or availability.

1957-1995 Sea Lion was located Philadelphia, PA.
Their production is now located Bellmawr, NJ.

It seems highly doubtful that availability of either grade could ever have been a factor in bolt selection. I doubt that grade 5 bolts are ever cheaper than grade 2 when purchased in like quantities from the same supplier. However the pricing is normally close enough that inventorying two grades of bolts vs one could easily be a factor - even if - say only 10% of usage instances actually requires grade 5.

Sea Lions web page on trailer selection includes just one mention of salt water.

Two things are necessary to assure a durable, long lasting trailer; heavy gauge metals and conservative design. We use 1/8" minimum wall thickness for all frame components on our 3x3 and larger frame sizes. If you've ever had a galvanized trailer fail after many years of service you know that the reason they fail is that something rusts out and collapses. Of course this always happens when you are on the road with your boat, usually in a lightning storm. It's usually the rear cross bar or the rear of the main frame rails which always get dunked in the salt water. The heavier the steel is to start with the less it flexes and the longer it takes for corrosion to weaken the component enough for it to bend under load. When you compare trailers look at the thickness of the components as well as their dimensions.

Sea Lion's contact page includes phone #, fax # and email address.

Were it me, I'd either contact them for their opinion about stainless or simply go with the grade 5 hot dipped bolts that OP asked for and seber provided a link to in post 13.

 

[FSrepair&fabrication]

Most of these replies are absolutely incorrect. "304" is more commonly called "a2" when referring to fasteners. "316" is close, but not quite "a4" in a fastener WHICH IS THE ONLY ONE APPROVED FOR MARINE USE. A4 is available in 3 types type 50 (soft) type 70 ( medium) type 80 (high stength). A4 type 80 is what the OP needs, it is within 5k psi tensile strength of a grade 5 fastener. We recently did some installation of equipment right on the bay. The engineer on the job gave me an hour long lecture on the types of SS fasteners and why we were using them.

 

[lis2323]

Stainless bolts are usually on the whole weaker, as long as you understand that proceed how you wish.

Once you over tighten a couple (or more) SS fasteners this becomes quickly apparent. [emoji849]

 

[DHCrocks]

316ss bolts are used to put together aluminum docks. docks are subject to a lot of stress in all directions. They are the fastener of choice for marine applications. If you are so concerned about using them just drill out the holes and go up a size so if it had a 1/4" go to a 3/8" bolt. in this example the 1/4" has a cross sectional area of 0.05 sqin, the 3/'8" is 0.11 sqin so it is more then twice as strong. a non graded ss bolt is 72k psi so if you doubled it it would be approaching grade 8 territory well in excess of a grade 5. or you could just use class 80 and call it a day

Be sure to use antiseize and use hand tools only. Don't use an impact gun, you need to go slow or they will gall and seize up. Do not overtighten, the threads are softer. Too much speed will tear up the threads once that happens you're going to have a bad day.

here's a chart for the strength characteristics

View media item 106760

 

[SeisMec]

1/4" has a cross sectional area of 0.2 sqin, the 3/'8" is 0.45 sqin so it is more then twice as strong

Yes, better than twice as strong. But cross sections are not even close.

Pi r squared.

The recommended hole diameter for a 1/4" coarse thread tap is 0.2010".
The cross section that hole is just less than 0.032 square inches.

The recommend hole diameter for 5/16" coarse thread tap is 0.258".
The cross section of that hole is just over 0.052 square inches.

The recommended hole diameter for a 3/8" coarse thread tap is 0.314".
The cross section of that hole is just over 0.077 square inches.

 

[DHCrocks]

you are correct, I mistakenly used the diameter of the bolt not the radius. but the ratios are the same.

 

[micdelbo]

I'm rebuilding and modifying a 2004 Sealion boat trailer that was, and will be, used in salt water.



Seems many of the original bolts were only zinc plated and not hot dipped, they're badly rusted and I need to replace them.


Is there a source for hot dipped Grade 5 bolts or am I dreaming?


I've tried all the online trailer specialists, I can find hot dipped U Bolts but not regular hex heads. They all sell SS hardware which is about twice the price and still not graded.


Any leads?

Do yourself a favor. After deciding on what fasteners to use and finishing your project, spray your trailer with Fluid Film or Wool Wax once or twice a year (depending on number of dunks in sw and where you live).

If you have never used them, you will be amazed at how well they work and the lack of corrosion that takes place.

I use it religiously on anything that I don't want to rust. I buy 5 gallons at a time to be able to spray large projects and brush on where needed. I still keep a bunch of spray cans around since they are convenient.

I don't live in a saltwater environment where the air alone can corrode anything, but 2 years ago when he visited PA, my friend on the intracoastal waterway in NC asked me how I keep my farm equipment that sits outside so 'shiny'. I told him about FF and he started using it. He is now a believer.

I wish I knew about it 20 years ago.

Sent from my Pixel 3a using Tapatalk

 

[bpjr]

Most of these replies are absolutely incorrect. "304" is more commonly called "a2" when referring to fasteners. "316" is close, but not quite "a4" in a fastener WHICH IS THE ONLY ONE APPROVED FOR MARINE USE. A4 is available in 3 types type 50 (soft) type 70 ( medium) type 80 (high stength). A4 type 80 is what the OP needs, it is within 5k psi tensile strength of a grade 5 fastener. We recently did some installation of equipment right on the bay. The engineer on the job gave me an hour long lecture on the types of SS fasteners and why we were using them.

Approved by who and exactly what is your "engineer" including in MARINE USE? A lot of empiracle evidence totally debunks needing A4 for everything marine. Example: Dock building with 304 has proven itself structurally but not appropriate for an inboard engine prop shaft under full time immersion...evidenced initially by a rash of crevis corrosion problems when it started replacng bronze shafts back in the 1970s. Application is everything when talking specs.

 

[FSrepair&fabrication]

Approved by who and exactly what is your "engineer" including in MARINE USE? A lot of empiracle evidence totally debunks needing A4 for everything marine. Example: Dock building with 304 has proven itself structurally but not appropriate for an inboard engine prop shaft under full time immersion...evidenced initially by a rash of crevis corrosion problems when it started replacng bronze shafts back in the 1970s. Application is everything when talking specs.

Im sure some random standard can be found on google to support what i was told. I dont think it's necessary to bother with since you said yourself a2/304 is not appropriate for immersion, which is what the op will be doing to launch his boat. So what exactly are you arguing about?

 

[RTM]

Deleted

 

[bpjr]

Im sure some random standard can be found on google to support what i was told. I dont think it's necessary to bother with since you said yourself a2/304 is not appropriate for immersion, which is what the op will be doing to launch his boat. So what exactly are you arguing about?

Lighten up, no arguing here. You stated most replies here were incorrect and I'm trying to find a credible source to back that statement up. I believe your engineer was stating some written standard based on a design specification and didn't mean every application on the planet related to "marine".

Trailer dunking and full time immersion are totally different applications. Successful examples are found everywhere and debunk "random statements found somewhere on the internet"...and as bad as using Wiki for credible info. Reread my earlier post, I stated 304 isn't appropriate for full time immersion. Dunking a trailer or docks getting splashed with saltwater isn't a problem.