Which Bolts are the Strongest

This should help you………. ^{I just check this last week.}

AS far as who or which bolt to buy, Check Fastenal (www.fastenal.com)

Bolt strength grades

As you have found out, bolts are not just bolts. For imperial designations, there are grades 2,5 and 8 with grade 8 being the strongest. You can tell the grades by the markings on the heads.

Grade 2 has no markings

Grade 5 will have 3 radial lines

Grade 8 will have 6 radial lines

If you need metric bolts, the grading system is different.

Fastenal will be able to get what you need in either imperial or metric, but there are lots of other bolt "suppliers" out there.

Bolts are normally NOT used in bending situations......

The Hyatt in Kansas City comes to mind.

Thank you for the technical explanation and details. As I said its been a long time ago and I only remembered the essentials. Since your post I have reread several the investigations that I read at the time of the collapse and soon after and refreshed my memory. One thing that impressed me at the time was the forensic detailed investigations that they did as a result of it. Do remember if there were any criminal charged against anyone involved? The ones I read did not mention any court actions, just technical and newspaper reports, They might have come after the reports were published.

Good Luck, Old Salt

This is a fish net. I don't think the human safety is an issue here.

Good point, all the same.

Human safety would primarily depend on whether or not any humans were within the (line-of-fire) of the failure.

During the big Alaska earthquake of the early '60' (?)s, pre-stressed and/or post-tensioned beams became (un-seated), and shot steel cables out of some of the structures by hundreds of feet.

Most previous passers-by were unaware that said buildings were essentially held together by steel cables at all. The survivors became sadly more aware afterwards...

One more thing that I omitted on my first reply. There are also structural bolts which have better strength than the standard imperial designations.

A235 - most common structural bolt - used in construction of fabricated steel buildings

A490 - a higher grade of structural bolt - can be used in normal steel construction as well, but more commonly used in steel bridge construction

http://www.boltdepot.com/fastener-information/Materials-and-Grades/Bolt-Grade-Chart.aspx

The only case that I know of where we put bolts in bending was for tubular transmission towers and substation structures. From memory, I think we used galvanized threaded A193, Grade B7 rods.

I would go with titanium bolts for high strength wet location high durability application....

http://www.industrialtools.in/productsub.php?prodid=13

Thank you all.

I have found a hardware store that services the oil and gas industry. Most everything in the store is made in the USA...no cheap imports.

For my use we decided on the Class 8 "yellow" bolts.

I do not know how things got started on the "bending" issue but I never wanted a bolt to bend. I want it to replace the all thread galvanized we had used in the past.

Thank you all again for the lessons on bolt terminology. It made me more comfortable speaking with the guys at the oil field supply.

Your application (bolt through two shackles) is exactly what a bolt SHOULD NOT BE USED FOR. That bolt is subject to bending in that arrangement. Given that it's for a net I guess it doesn't matter.

Since the fish will die anyway. :()

Ha. Good one!

No offense, but why?

No offence taken. Most people (...pointing finger at folks in this thread! ) refer to an application like the one you've shown as a pin or bolt in shear but...it's actually not. Pure shear conditions occur only in very specific mechanical arrangements where there is zero gap between the wall of the component being loaded and the wall the pin or bolt is passing through (these are referred to as "shear planes" in engineering nerd talk). The clearance between pin or bolt and the hole also has a significant effect. In your application, there are significant gaps between the shackle and the gussets where the pin passes through. I'm also assuming the clearance hole for the pin or bolt is relatively loose. This means your primary mode of failure (given sufficient load) will be in bending and not shear. See below for a simplified representation of how your pin or bolt will tend to "bend" given your arrangement.

Am I correct in assuming your bolts that experienced "some bending twice in the Chukchi Sea" looked somewhat similar to my illustration?

That is exactly what they looked liked.

I'm not just a pretty face!

Cheers.

From your OP, you gave the impression that you didn't want them to bend, you asked for rigidity, so we worked on that basis, suggesting ways to increase rigidity and some wanted bigger bolts, a couple of us wanted spacers to force the shackle against the plate to make shear the controlling case, and one who wanted a tube over the bolt and the shackle over the tube. All this before it came out that you wanted the bolt to bend under an unusually high load.

I'm not complaining, some of these things need some to and fro to get the whole problem. Your problems always seem to apply across several disciplines so we learn from each other.

GA

OK, that makes some sense. Is a 5/16 Clevis pin as strong or stronger than a grade 8 bolt of the same diameter?

A cotter key probably holds the bottom?

It isn't necessary the material strength that makes it the best choice. It is the process that it's made.

Pins could be drop forged and gives it more toughness ..... ^{(I think that's the term)} has to do with the grain of the metal.

Reference: http://thelibraryofmanufacturing.com/forging.html

Remember there are compromises in physical metallurgy. Something could be stronger, but the fracturability is higher making it a poorer choice.

One of our esteemed members Milo is quite knowledgeable in this area.

Check his profile, I'm sure he has a few good answers that can reference this very thing if your interested.

That explains it much better.

one is more 'aligned' in its formation than the other.

Lonster has the correct part (clevis pin) for you application. Bolts are only rated for torque (stretch) and not lateral (side) loading regardless of the material they are made from. One should never use a bolt in a side loading scenario due to the possibility of catastrophic failure.

hitch pins are also an option. made of 1039,1045 or 4140 steel with a rockwell hardness of 38-44. This gives them a high shear strength.

Like a trailer pin. Excellent idea if they are as strong as a Grade 8 bolt.

thank you.

Moosie made a good point. what exactly are you looking for here? what application are we talking about?????

Just look at the pictures, it shows what I am doing.

okay I see now! basically I don't think you need a stronger bolt as much as you need a sleeve covering the bolt! THE SLEEVE has to be tougher than your hinged pieces.a typical grade 8 should be fine but in a marine environment Id go stainless

Grade 8 has a higher torque strength but is relatively brittle for shear strength. IE: Grade 8 will snap and shear off with sufficent latteral force where a softer steel(grade 5) will more readily "flex" but stay intact.

We use grade 5 plow bolts for this reason as they are less likely to shear(break) when shocked by an impact on our plow trucks.

fyi,

In a tension test Grade 5 would show a more noticable necking (deformation) before failure, as opposed to grade 8 which would show less.

Exactly, In our application you have an opportunity to inspect the blades for damage pre-road trip using grade 5 versus grade 8 that visually looks ok untill it drops a plow blade in the street.

This is slight off topic from the OP because your bolts/pins are in shear, but good foundation knowledge. And one gets a good overall on what's going on.

This requires Java, but this is a good animation for necking on a tension test on a stress/strain diagram.

http://www.esm.psu.edu/courses/emch13d/design/animation/Fnecking.html

And of course a wiki link for good measure.

https://en.wikipedia.org/wiki/Fracture

In the past, we had used simple non graded threaded bolts. We moved into non graded carriage bolts. Either way we had no serious failure...some bending twice in the Chukchi Sea when the R/V got caught in some 20' seas with the gear out and the net hit bottom a few times riding down the swells. they scooped up about 1200 lbs. of Brittle Stars and a like amount of mud.

However, as long as the nets are operated in a pelagic environ, there has never been any issues. Load cell testing showed us years ago the Bollard pull was under 700-800 kg.

I am going to try the Grade 8 x 5/16 for now BUT will look into this Clevis Pin idea.

The Titanium is a winner for sure, but I want something to give WHEN these scientists hit something they shouldn't.

Once again, thank all of you.

Be on the look out, next month or so. I have project that will require Rube Goldberg type thinking ( if you all are old enough to know what a Rube Goldberg is). I hope you all are up to it....its the most intricate thing this ol' guy has ever tried!!!!

thank you all for the input on this one.

From my personnel practical experience, as some others might agree, if there is any question concerning the capabilities of a bolt and it's grade, go up to at least the next higher grade. The cost of the bolt upgrade during fabrication or installation is usually insignificant as compared to the cost of damages should it fail, the costs of getting to the bolt to replace it, the cost of loss of business if applicable and lastly the cost to your personal pride when the boss finds out.

From McMaster the cost of a steel cap screw at grade 8, 3/4"-10 x 6" is $4.70 ea, grade 5 - $3.11 ea. and grade 2 - $2.88 ea. The higher cost is insignificant as compared to the cost of bolt failure.

As explained , I believe I am where I should be with a safety factor built in that WHEN this rig hits bottom in some shallow bay, the bolt will bend and the door or doors will lose its Angle of Attack. The Horrific Wobble that will follow on the towing warp will lets these guys know ( if they read my CAD Cartoon Instruction Brochure) they need to pull everything in and examine the gear. Hence I pack them several replacement bolts which will now be Grade 8.

Are you old enough to remember shear pins, in props, on outboards? Same effect I want.... sort of...

Thank you all again. ca ce bonne!

a grade 8 shear pin...that's new

Netmaker-

Physically my body has replaced many shear pins on outboards, snow blowers and numerous other industrial equipment. In spirit, I am not as old as I may look. I am too familiar with numerous pins on outboards from having to change several while I was holding on to the skeg (lower end) because the charts were incorrect. Also shackles with clevis pins and the screw type clevis pins ranging from 1/4" to 6". The 6" ones are heavy enough to bust a _ _ _ (this shares the same name as what is threaded onto a bolt).

Glad you have some Ideas for your solution!

Good Luck, Old Salt

Bolts have nuber marier on the head. Called classe in ISO system: 6.6 8.8 10.9 and more. Tell me fou location and I clan help you to fini good bolts

Thank you. everything is already done and sent on its way.