What happens if you back off a shackle by 1/2 a turn? 

Notes before you comment: 1 At ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-9mYzflG28uw.html there is an error, transposed the 1/4 and 1/2 turns, sorry. 2 "Hi Robert. I'm a metallurgical engineer and do a lot of work in fastener metallurgy. Those three tensile tests are all within expected scatter for wrought steel parts (both for breaking strength and elongation percentage). If they had run ten samples of each condition, I would predict that the range of the tight, 1/4 turn, and 1/2 turn groups would overlap almost completely. I would also recommend anti-seize grease on the threads. This will prevent binding when removing the pin after use and prevent thread corrosion while not in use." - elektro3000 3 "The quarter turn was taught to sailors in ships anchor gear. There number one concern is corrosion and the ability to slip an anchor. Shipboard shackles are always moused closed so being able to break a shackle free of its pin when it has been siting in salt water for years is more beneficial then a three percent working load loss." @petercaires9276 1 hour ago 4 Sample size - I draw attention to the fact it's only three shackles. That's not as conclusive as 30. However, it's proving a negative; if backing off made a dramatic difference, then it'd show up for sure even in that small sample - consider a shackle with a cut halfway through its pin, you'd wouldn't need a big sample to show that's weak. Not trying to prove that for example "all shackles break above X kg in which case if we took only 3 the 4th could be weaker. I've also broken other shackles before, and they all had consistent results, and they are built to standards. This gives me confidence that the sample size could be small and still useful. ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-AVqYkgaaKAY.html Also, these shackles are made to a standard which gives you confidence they will all perform identically. Soft shackles are not, so you need a larger sample size. 5. The pro riggers and doggers disagree: "I was in the heavy rigging industry for 50 years. We generally back off the pin just a fraction, not a 1/4 or an 1/8th. Fully tightened you’d have to get a wrench to get it loose if you didn’t. I understand you could weaken the capacity by doing so but we never put a shackle anywhere near its maximum. All equipment and rigging has a built in safety capacity. When rigging gives way it was either damaged or overloaded." "I m so used to snugging the pin to the shackle it is foreign to do it any other way. This coming from heavy rescue in the fire service and also dabbling in heavy recovery with a local towing service including working off of a 50 ton rotator wrecker and pulling and lifting some monstrous loads. Their company policy is that all shackles are seated to the shoulder of the pin. I would indeed love to see the research that has been done to prove that the pins could become unscrewed in certain situations. Perhaps heavy vibration or extreme/ excessive movement of the rigging. Thank you once again Robert, keep it up man!! Cheers from the US" There are definitely varying views even amongst the professionals!

Hi Robert. I'm a metallurgical engineer and do a lot of work in fastener metallurgy. Those three tensile tests are all within expected scatter for wrought steel parts (both for breaking strength and elongation percentage). If they had run ten samples of each condition, I would predict that the range of the tight, 1/4 turn, and 1/2 turn groups would overlap almost completely. I would also recommend anti-seize grease on the threads. This will prevent binding when removing the pin after use and prevent thread corrosion while not in use.

Professional heavy recovery wrecker operator of 41 years experience here. I completely concur with your assessment. I work daily with equipment and loads fully capable of destroying that screw pin shackle, and I have ruined several over the years. I have never pulled one to complete failure but deformation comes well before failure. I train to normally back off 1/4 turn but for an important reason you didn't cover. When we go to remove the pin after a recovery that was set at 1/4 turn and find we can't loosen it by hand we know the shackle was exposed to plastic deformation. In other words we know the shackle was damaged and needs to be removed from use. We then screw the pin in from the opposite side to mark it as damaged, then back at the barn we destroy it by cutting it apart. The only exception to the 1/4 turn back rule is a situation where we fear it could become loosened. Such as rigging that will be used over and over to lift items or pallets of cargo onto a trailer. In this case we tighten with a tool and put a zip tie through the hole to insure it can't back out. The zip tie also serves as a visual flag that can be inspected at distance showing the pin hasn't backed out because to do so would bust the zip tie.

The quarter turn was taught to sailors in ships anchor gear. There number one concern is corrosion and the ability to slip an anchor. Shipboard shackles are always moused closed so being able to break a shackle free of its pin when it has been siting in salt water for years is more beneficial then a three percent working load loss.

I was taught the half turn back off... purely so it makes it easier to undo the shackle. Under load it tends to tighten up so if already snug, it will be tightened beyond what you can undo by hand. Backing off half a turn gives the pin some wriggle room but you can still undo it by hand. This was in the Royal Australian Engineers and the thinking was you have to undo the thing under fire or hanging onto something with one hand and don't want to have to faff about or scrabble for a marlin spike or shifter. Great video as always.

I had always assumed the advice to back off the pin thread more about being able to get the shackle undone after loading it rather than making it stronger.

So long as you have a shackle rated appropriately this will not be an issue.

Another great video. It's really helpful that you provide evidence to support the conclusions, but especially good that you encourage us to focus on what matters more, rather than fussing over things that hardly matter at all.

Thanks for the very informative video! I appreciate you putting this in perspective to help us better understand the things that are important!

I m so used to snugging the pin to the shackle it is foreign to do it any other way. This coming from heavy rescue in the fire service and also dabbling in heavy recovery with a local towing service including working off of a 50 ton rotator wrecker and pulling and lifting some monstrous loads. Their company policy is that all shackles are seated to the shoulder of the pin. I would indeed love to see the research that has been done to prove that the pins could become unscrewed in certain situations. Perhaps heavy vibration or extreme/ excessive movement of the rigging. Thank you once again Robert, keep it up man!! Cheers from the US

Thank you for this, You answered many questions i have had for many years👍

Great video as always. On rigging courses I have done they always say seat the pin fully, this is normally company policy for liability reasons but also they talk about repeated use of equipment. Having it backed off a bit allows the shackle to expand slightly under a side load, this process repeated over time expands the shackle and weakens it according to to courses I have taken. Now obviously there is a lot of health and saftey regulations in the rigging world but it's nice to see actual test that backs up that it's still safe enough to back off a pin in light 4wd recovery.

Thank you Robert for another excellent video.

One major component that was left out, is that the screw pin shackles are rated for opposing angle pulls on the bow side of the shackle. In that type of pull you will start to spread the legs of the bow LONG before what was shown in the straight line pulls of this video. So yes, in all reality it doesn’t really matter in a straight line pull. But if you have opposing pulls on the bow of the shackle, like when a tree saver is connected with a shackle, or a shackle being used as the center point of a bridal, the screw pin should absolutely be shouldered against the bow.

Another great and technically informative video. Invaluable information 👌

Excellent and straightforward video!

Wonderful, facts are nice to see. Plus your practical advice

I’ve been involved in hoisting and rigging for 30+ years, working with iron workers , crane operators, millwrights and I’ve never seen anyone back off a shackle. They were designed and manufactured a certain way for a reason. Seat the shackle bolt all the way.If it is tight , use a wrench or drift to undo it, that is why it is flat and has a hole in it.but agrees that in 4x4 recovery the point is mute.

Love your work Robert ! Thanks. I'll always 1/4 turn back off

Good job of putting the focus where it needs to be.

AWESOME. Just AWSOME! THANK YOU.

Great info but great backdrop. Click on you as the machine fed it to me. Got good info. But absolutely love your back drop. Most creative one I have seen. Even without doing RU-vid, I may find my own type in a garage or bar someday

When I was in the Navy as a boatswain mate we were required to tighten the shackle tight and add more force with a marlin spike to bury the threads.

Very good information. Thank you.

Great video and sound words 👍

I was in the heavy rigging industry for 50 years. We generally back off the pin just a fraction, not a 1/4 or an 1/8th. Fully tightened you’d have to get a wrench to get it loose if you didn’t. I understand you could weaken the capacity by doing so but we never put a shackle anywhere near its maximum. All equipment and rigging has a built in safety capacity. When rigging gives way it was either damaged or overloaded.

Great video. I've never actually needed a shifter to loosen a bow shackle and I do them up finger tight.

Great factual info as usual. When you mentioned twisted straps I immediately thought of the Fireball Tool video! For excellent technical recovery videos, I watch "Florida Off Road Recovery". Matt regularly recovers vehicles much larger than his with a winch and multiple snatch blocks - he is a master. He, like you is very factual and knowledgeable. Love your videos.👍

Great video!

Good thought exercise, thanks. Take away? Shackles are way stronger than needed for basic offroad recovery use. Don't let them get overly corroded and don't lose the original pin and you should be good.

Hi Rob I commented a while ago but this time we agree, am liking ur line of thinking which I utilise every day at work......if it ain't gonna come into play doesn't matter if ya back it off or not .. Nor if the slings have a twist .... as long as the person rigging load or setting up the recovery gear has a mech mind and knows of potential failures in his set up. He and rerig if red flags pop up during recovery. Love the channel keep up the quality sharing of knowledge! Chur

I don't back off a half turn, but I don't tighten the pin all the way either. If you put it on tight it won't come off by hand.

Thank you for this video, it's great information.

Great video, thanks

To get a riggers ticket in Australia you have to know that when you do up a shackle you always back it off bit, no matter how big the shackle or load, or you don’t get the ticket.

Thanks for sharing this information. 👍

T shirt to a skivvy (without a roll neck) and back, seamlessly; quite an impressive feat. 😃 I didn't know about the knob position on the soft shackle; always learning.

Im a tank commander in the canadian army. We always turn back 1/4 turn when doing recoveries. Our shackles are rated for well over what we are usually going to put them through. Being able to remove the shackle is very important! Ive had inexperienced guys hand tighten shackels and after a recovery we had ro wait to get maintenance to cut it off witha torch.

If you’re breaking shackles, you’re using an underrated shackle for the operation or grossly improperly rigging.

the hole in the pin is for safety wire tie so it can never come lose on you even if you have it backed out a turn or not

Thank you.

I was a Chain and Rigging Certification Technician for 9 1/2 years and what I got all the time from riggers is they were taught it so it was easier to undo afterwards. I would show them that as soon as you back the pin off slightly the whole pin can rock in the thread left and right and tell them that it is the same as using Eye Bolts and that the flange of the pin shank is supposed to make contact with the mating surface. I would also ask them "when you have backed it off a 1/4 turn is the pin still tight after your lift?" and they will say "yes" and I tell them it is because the shackle has stretched very slightly and every time they back it off it will stretch very slightly each time until the pin does not reach the outside edge of the shank in the threaded hole as required under specs of the shackle for use. I have seen shackles get a lateral force sideways on the pin and spit the pin out partly due to bad rigging of load. it is definitely the repeated cycle though that did the main damage of them stretching it slightly more each time. (and that was with staying withing the lift rating also). our visual inspection on them would start with checking all parts for wear and damage and include seeing the pin when screwed all the way in reaches the outside. other dangerous thing I would find all the time is mismatched pins and bows and some had even fitted imperial pins into metric shackles and vice versa. (the thread being metric or imperial I mean) and they may fit and do up but it leave the pin more prone to being spat out. with the pins on shackles the original reason for having a hole in the pin was riggers could put their marlin spike into it to undo them, a lot would carry one as they used them for aligning parts when craning in. I would train engineering students a few times a year at a local Tech Institute and deliberately break a chain in my mobile testbed to show them how fast stuff moves when it breaks. my testbed could do up to a 30 Metric Ton pull so I could test up to 20mm G80 chain anywhere in the country.

I tend to prefer rated lifting slings for tree trunk protectors or bridles because you know what they actually rated at. Interesting video.

I prefer to finger tighten and not back off… the issue is more about vibration over long periods which may undo the pin. But, not an issue for a quick recovery. In a long term situation I would normally tie the pin to the bow with a wire.

Great video and thought process of time management during vehicle recovery. I didn’t get the same numbers converting the lb. to kg results for the 3 trials, but it seems like it was a relatively small difference given the breaking strength of the shackles tested.

Dig with a shovel,I thought everyone was allergic! I thought that’s why everyone spends thousands on winches and recovery gear, so they don’t have to buy a shovel? Great information,but I’m pretty sure most people still did not hear you say dig! Thanks from all of us who own a shovel

In the US, a lot of folks drive around with shackles hanging from the vehicle. In those cases I always recommend turn them till tight or turn them then back off 1/4 turn but put a zip tie through the pin hole and the shackle so the pin can’t work itself loose and fall out.

It's pretty wild to see that thick shackle deform like clay!

ive worked as an electrician for industry, in plants. building the plants themselves. every time we lift something with a crane, the shackle bolts are just-before-tight, or a quarter turn. but usually we are using 8 inch shackles, up to 20 inch

It was close to the end of the video he mentioned to look under the vehicle to determine why it's stuck - golden advice. Imagine that you got hung up on a rock at the front pumpkin (or another critical item) you rig up the winch for a pull then rip out the front axle out when a simple jack and block could have freed the vehicle? Comments below mentioned leaving the shackle 1/4 turn loose to indicate if the shackle experienced deformation if it is tight when you're done with the pull you may consider replacing that piece of gear.

Interesting as usual. In the different situation of travelling with a load ie using shackles with a trailer - I always do them up tight because I am concerned that the vibrations will loosen them esp. if they are already loose.

That's incredible the amount of load it took !!

Hello Robert, again outstanding results and justifiable conclusion, especially with in line pulls. Be interesting to see what would happen at side pulls, which is where I think many vehicle recovery scenarios are concerned. Even in side pulls the screw pin bow shackle will probably be the last thing you have to worry about breaking. Well done Sir and thank you for your outstanding education.

Interesting , Thank You.

I'm really curious as to the breaking strength of the 5/8 hitch pin we all use. Both in single shear and double shear.

It was taught to Off Roaders so they could remove the pin 📌 by hand after an extraction

I was taught that backing a shackle a quarter turn is to help mitigate the occurrence of the threads being warped under load to the point of binding. that way if you're up on a lift and have to for some reason undo the pin you are less likely to need a tool to do it. In the case that you can't undo it by hand you have bigger problems that need addressing before anything else is even considered. I don't know how true that is but I always followed it because I had never seen anything to the contrary.

A few seconds thought by anyone with some metalurgical or mech eng experience clearly should indicate that the "snuggness" of the pin in the loop of the shacke is no going to make any appreciable (ie statisically valid!) difference to the UTS because of the failure mechanism caused by where the shackle actually yields! It's clear that at the point of ultimate failure, ie where the minor diameter part of the pin thread transitions to plastic deformation, necks and hence experiences a run-away failure, the pin is ALREADY very bent as mentioned, ie even a loose pin at this point is not actually loose anymore! In order for the pin to fail in tension, then it MUST be hard up against the shackle loop. In all theses tests, far far before UTS failure the shackle pin will not be removable because deformation of the pin irreversably locks that pin into the shackle loop so it cannot be removed as it can no longer be unscrewed. I suspect that a test with a grossely un-mated pin would actually not be that far behind in terms of UTS, although the failure here would not be overal plastic deformation but localised bending moment stress concentration at the base of the thread leading to crack propogation. Looking the video and the stress strain curve, id suggest this happens at around 50 to 65% of UTS, ie a long way before the shackle actually fails. In a real recovery situation, if you've bent the pin, the shackle is scrap, well before you were in any risk of breaking it. Obviously, this is done on purpose by the specific design of the shackle to make it safer, ie to indicate to the user they were getting close to a failure before it actually fails. This means it's basically irrelevant how much you back off the pin after fitting it (within reason obvs 🙂 )

Thanks!

Working offshore oil and gas diving, we snuged them up and backed of just a hair, but with the size and loads would still need a shackle breaker on larger stuff. How shackles got put on matters as well so they couldn't unscrew themselves if working in the water. Not as big of a deal offroading, but the take home is having the right size rated stuff (+safety factor) comes in clutch, especially if you have to get a little cowboy with things.

I am an instructor for a steamfitter apprenticeship program and I believe that the issue with the “backed off” shackle pin is the possibility of the pin coming out from vibration. The likelihood is I agree low but it is even lower if the pin is jammed tightly. Reducing the risk of failure is the chief important issue when engaging in overhead rigging.

We Use these swinging trusses for pole barns... I constantly check these. Last thing you want is one backing itself out when a truss is above your head. And they do back out.

That was great info, thanks Robert. You may want to check the conversions or perhaps a transcription error n that chart.

Thanks for that. I'm sick and tired of being told to tighten it or loosen it👍 and while people are watching fireball tools check out the file dragging. Ha ha now the cats amongst the pigeons.

As a rigger we use the 1/4 turn back off to make it easier to remove the pin, as the strength difference is negligible

Good video

Steel Iron worker structural fabricator here... If you don't back off at least the 1/4 turn it will be impossible to undo without tools. That means it will wear out quickly.

Robert I keep proper lifting gear with ratings in my work rig, never need to worry If you use products with CSA safety ratings

The biggest thing about the measured standards that are on the shackles is, they were done with the 1/4 turn clocked off the bolt in the first place. The greatest thing about these shackles is they were designed to be utilized without wrenches. There is a greater chance of binding if you were clamped in tight. If I'm doing a long distance tow with a shackle, I'd tie the bolt off so that it won't 'go anywhere'.

Question: If I want to connect a g8 chain (8mm) to a snatch strap what is the tool or part used for that. The bow shackle does not seem to go inside the hole of the chain. thanks

From an experienced heavy lift rigger (designing the rigging for very large crane lifts such as bridge beams, HVAC equipment etc) we design the rigging so that the MAX load on any part of the rigging including shackles does not exceed the rated value ( which is much less than deformation or even failure). The reason to back off a shackle pin is not to increase strength, its to prevent the shackle pin from rotating and getting super tight under load to the point it can not be removed by hand. IF you stay withing rated limits of the manufacture, you should not have a failure just because you backed it off a 1/4 turn.

Here's an interesting fact. I can only speak for Crosby as I do not have tolerance specs for other manufacturers. Crosby publishes acceptable shackle pin shoulder clearance which is acceptable even after the pin is wrench-tight. This is hard for many riggers to accept as they are usually taught the shackle is no good if the pins do not shoulder out. It is sad that Crosby shackle quality is not what it used to be and I see many companies switching over the Van Beest Green Pin shackles. Their castings are much smoother and they do not use raised lettering. The later is important because raised lettering is tough on synthetic slings. Another point is Van Beest and some others counterbore the shackle ear to allow a full diameter pin to engage the ear. Crosby, CM, Campbell, Chicago...they use a fully threaded ear and so you have a good pin stress riser right at the shackle ear (where the pin thread starts). I've swapped over to buying Green Pin or even Skookum shackles for the projects I do for Bechtel. Green Pins are half the cost of Crosby. Last time I checked, Skookum shackles were cheaper than Crosby alloy shackles. The use of Dyneema or Spectra synthetic rigging has made the use of alloy shackles more necessary so that the shackle isn't the weakest link.

What is the rated strength of the shackle vs. where it broke? It's my understanding (& experience) that the backing it off is for ease of removing (un-rigging) said shackle when up in the air it is easier to remove if any binding was put on during lifting. Also, I've never been involved in a rigging that was not way overly safe, where the weakest link was still rated 2-3 times over the actual load. I don't think that there's ever a reason to try being a limit tester.

The debate on if you back off a shackle half a turn or not in four wheel drive recovery is less so about shackle failure and more about it not becoming a projectile if the pin works loose and comes out. I’ve seen a pin in do itself half way through repetitive snatching.

The shackles i use at work for lifting are much bigger then those. But i always back them off a bit because if you dont after the weight feom the lift is put on it you cant get the pin to turn by hand i usually have a wrench nearby but just a pain.

When doing vehicle recovery a 1/4 turn back and on trailers and other uses to tighten how many shackles do you see on the roadways

The threaded pin is what sheared off and failed, right where the threads begin, all three times The shackle bent but didn’t break

SWL 4 3/4T They are meant to pick dead loads not shock loads. The main reason for backing off a 1/4 turn is when the crane starts picking the load and the chocker or load being picked will actually turn the pin and chinch it super tight. When the load is landed you need a tool to break the shackle pin loose. In construction you only use 80% SWL

what is your opinion of the Warn 8274 Compared to the newer winches. i know they should last longer and appear to be made from better materials

Another great testing video, I’ve never gone a full 1/4 turn back I’ve just cracked them loose before my pulls. Would you be interested in looking at forward notions jowl shackles? It’s not a threaded pin but two J hooks that are supposed to mesh together and hold onto your strap. I think they’re an interesting design but have not used it me yet myself.

14:10 this is where a high lift jack is useful - jack it up, fill the hole then tip it over. Anyone running high lift jack hasn't discovered other options unless they need to move the vehicle from one side to another.

Well done, all within margin of error

As a Machinist I learned using shackles for lifting using chains or straps, you hand fasten the shackle .

You remind me so much of Bill Murray in Caddy Shack when he is talking about types of grass. 😊

I have never backed off my shackle and I have never had an issue. However I use shackle that is rated for 4 times my usual pull weight.

Can't tell by the camera angle but the one thing that I noticed is with the pin loose the pin bowed out farther until the opening of the shackle came down tight against the testing fixture ring? If the test fixture rings were smaller how much would that effect the end result? I'm guessing that results would be different.

backing off the shackle a quarter of a turn isn't about failure of the part. as you said, you'll most likely never see that kind of load in 4-wheeling. it's more about being able to turn the shackle pin without having to resort to a crescent wrench to loosen it.

I've noticed heavy recovery operators use a nut on the other side of the shackle.

Former u s navy is how i'm gonna be talking on this one. Twist that shackle pin tight wire. It must not fail in users and service. And the only way to keep it from failing and usage and service. Twist it tight wire it and keep an eye on a check at once in a while.

I've always tightened them, mainly because I've seen 1/2 turn, vibrate into 3/4 of a turn. I've never seen a tight one vibrate loose during a recovery. I could see it for riggers, and the afore mentioned ship anchor guys, but I'm neither of those. And I own a wrench in case it gets too tight.

If you're using a shackle that would break due to the pin being backed out any amount you're using the wrong shackle. I thought it was hilarious when you said "you'll be in space or hospital". 😅

Just don’t back them off. They’re designed to seat in. Don’t be lazy just use a tool to release the shackle is required after loading. 😎👊👍🇦🇺

The video shows when backed off and not backed off they both exceeded their cert breaking load.. and they were within 3% of each other which is insignificant compared to real world variation of used kit in the field. So this proves that backing off doesn't weaken it (and makes it easier to undo afterwards). Argument settled 1/4 back off it is then! Thanks!

there's an argument to be made for fully tightening and using a witness mark on the threaded end. in the event the shackle fails in a situation that would be highly unlikely to exceed the working limit, you'd have a better case for a product failure claim.

The difference is probably within part variation and margin of error. The reason for backing off again is - so I thought - not to increase the maximum load, but to make it easier to open it up after it was within design load.

I'm curious how much difference there is in how hard the pin is to remove once the shackle is stressed depending on if it was backed off or not.

If you need a shifter to undo the screw on the shackle after use, wouldn't that indicate deformation of the screw pin has occured due to an overload situation? I always thought the 'backoff' was for later ease of unscrewing the pin after time in storage or left out in the elements because you are then only overcoming the minor binding in the thread and not having to contend with the added binding of the shoulder with a snug screw fit.

Anybody that has ever used shackle's very much knows that the shackle will tighten up when lifting or pulling the load. Have you ever lifted 5,000 lbs like that? Try to unscrew the bolt after that lift. Even with a crescent wrench you will have a hard time getting it started. And for the knuckle heads a straight lift has less tension on the cable or strap than a vehicle stuck in the mud or sand. I've seen it happen several times, Goober trying to get that bolt unscrewed after tightening it all the way down.

If it is loosened, vibration can back the pin even more, possibly till lost!

Another here for backing off to make removal easier...I always thought this was just what you did.... 🤷🏻‍♂️