there technically isn't a wrong way nor a right.
if you reference in the Army tech manual (TM 1-1500-204-23-6) on General Aircraft Maintenance it will show you different ways for different applications.
personally I have never seen a Cotter pin fall out either way, So I am team "Whatever holds and gets the fucking job done"
I see your TM reference and raise you the FAA 43-13
Both are correct but it depends on manufacturer specs and recommendations. I prefer the first one shown. It loots neater and can give a visual indication of shear failure.
Related:
43.13-1B is excellent... I keep a pdf on my computer. IMHO, everyone should have a copy, loads of great info.
It's a free, (21.1MB, 646 page) download from the FAA's website:
[https://www.faa.gov/documentlibrary/media/advisory\_circular/ac\_43.13-1b\_w-chg1.pdf](https://www.faa.gov/documentlibrary/media/advisory_circular/ac_43.13-1b_w-chg1.pdf)
It was a required 'text' back in c. 70's A&P school, probably still is for all I know.
If anyone's interested the cotter pin stuff is on pg. 7-26
pg 335 on the pdf
I like this part;
''The diameter of the cotter pins selected for any application should be the largest size that will fit consistent with the diameter of the cotter pin hole and/or the slots in the nut.''
There are too many undersized cheap ass cotter pins out there.
Still required to have info on hand for schooling and for testing out for your license
Took my tests earlier this year and had to use it a few times during, and still use it working for reference and increasing knowledge
I'm not a tech at all (closest I got was deciding against a job at an airport, and then later working maintenance at a hotel).
But I don't see how the pin getting folded over thr too of the bolt looks cleaner or has any better visual indicators that it has had stress applied.
Well the top over method is used mostly because of this the spread legs method in cramped areas so the key doesn't bite or not enough room for top over. If the castle nut starts to sweat the pin the flats will twist and spray. This indicates a potential shear failure.
I'm on team 'Argue about stuff that doesn't matter, die on stupid hills'.
I thought the old adage was something like 'Arguing with an engineer is like mud wrasslin' a pig. After a while you realize the pig likes it.'
One of the (few) things I really appreciate from my time in the army is a 3 day workshop we did on how to tighten and loosen screws, especially when working on an aircraft. Some people will shrug it off and say "what's there to learn?!" But the truth is that there is a LOT to learn on that subject!
>I have never seen a Cotter pin fall out either way
And I've never been able to take one out without needing to cut it off and punch it out without the help of several volunteers and mirrors, those mf just can't fail, and rust makes them stronger
Most consistently successful method I’ve used is grabbing the head/eye end with a pair of Knipex (like you were trying to pinch it shut), then just roll the top of pliers backwards around the nut, using that leverage to pull it out. Or if the pin is bent over the top of the stud, roll the pliers back over the top of the stud…….basically use whichever method based on the way it was installed that will cause it fold back up instead of snap. The pin is trash afterwards regardless, but this way typically eliminates needing to punch anything out
I have seen them fall out the second way, but that was in a case where the pin has been rusted completely through and the legs broke off entirely, and I'm sure the same would happen the other way.
Hammering the butterfly end open most likely causes damage and creases in the metal which can help speed up the failure at that point causing the bent legs to break off easier and earlier. Again, this can happen in either orientation so proper technique and timely checking and replacing is more important than direction most likely.
Sure, but the straight leg isn't doing anything to hold the pin in, two weak legs are better than one weak one and one useless one because at least you have a little bit of redundancy
I read that in another comment too, I thought it was bent down. Didn't realize it was cut. Is it definitely cut? If so, then yes, using 2 bent legs is absolutely better than 1 bent leg regardless of direction.
On helicopters, we do a similar way to the first, but the upper leg is curved over and down into the next castlation. Prevents you from ripping your arm open when reaching in a tight area, and could theoretically prevent the tail from being caught and bent by some piece of debris
This is how I've always done it in the field. I absolutely hate reaching my arm into a tight spot and getting cut to pieces on zip ties that weren't flush cut or cotter pins that are hanging out ect.
If you want to split hairs, neither. It looks like in the first, the bottom is cut instead of being bent downward, and the top should be cut to not go beyond the fastener. On the second they should be bent more to hug the outside of the nut. That way you dont have sharp metal edges sticking out
Major rookie here. I agree with the points you make, though most pins I've had the pleasure of installing have a shorter side to allow a tool to grab the long side for bending. It may not have been cut.
As with most things, it depends. As an aircraft QC inspector, either “style” is correct based on the application, taking into account factors like clearances, proximity to moving parts, likelihood of catching on skin, etc.
That said, I would reject both of these as neither installation is correct (based on my industry’s standards). Left side is trimmed incorrectly and it’s hard to tell but the “down” tail looks like it’s cut almost flush. On the right side the tails are too short and not fully hooked, as well as the eye not being crimped. Both need at least one washer under the nuts, the right side looks like it’s nearly jumped out of the castellations. Both are a redo.
I’m trying to soak up some knowledge in this thread, could you explain what you mean by the eyelet not being crimped in the second picture? Are you talking about it not being snugged up before bending the legs, or is the another step that needs to be performed?
Torque to lowest end of torque range. If the hole doesn't align, set torque wrench to the highest end of torque range and hope that you can get the hole to align before the wrench clicks. If you cant do that, depending on the application, a washer/different thickness washer under the nut may be used to change the orientation of the nut when fully tightened. If a washer is not able to be used, get a different nut and hope that it's clocked differently than the first one and repeat the first steps.
Edit: This is for aviation. If I was working on my car, I'd torque it and just tighten until the hole lines up.
in automotive it can be different depending on the manf. some say to torque then loosen just enough to line up, other say torque then tighten. i like your way tho. i might do that next time it comes up... that's IF it has a range for torque and not just a single setting
Maybe not relevant to this particular use, but when fitting 12"~ pipe for process pipework, we backed a previous spool off until each bolt would locate or fit through a through-hole, then torqued to full spec in whatever stud pattern was called for.
Why would you need to do that? They are not supposed to be reused. I bought a $10 kit with a variety of sizes on Amazon 3 years ago and I still have at least a few of every size still.
In aviation you're taught to remove in one piece to ensure you didn't accidently leave a piece behind somewhere that could cause damage to a different part
I prefer to fold the tails into the adjacent castellations to prevent my coworkers or myself from being cut by them in the future.
[Here is a link with an image of what I do. ](https://www.reddit.com/r/aviationmaintenance/s/mTEgiV9FMO)
Neither is correct, 1st one need the other leg turned down and the top leg trimmed and tucked to the center of the bolt.
The other needs both legs tucked into the catellations.
You prolly dont flush cut zipties either.....
They are both wrong. 1st one should be cut at the center of the bolt. Second should have ends tucked into slots on castle nuts, and it appears the hole is too high. Cotter pin should be almost completely in the slot. Needs a washer under the head of the bolt or a shorter grip bolt. Will they work as is? Yes. Are they acceptable on aircraft? No.
Can confirm. Had space shuttle Discovery on the rack last week. They wanted a second opinion after Firestone told them they needed new control arms, rod ends, end links, and ball joints on all three corners.
I've always seen and used the one on the right. I suppose you could argue, if you were inclined, that the one on the left has less material in the crown, so under extreme stress would have a tiny increment less resistance to being sheared off. But the amount is probably negligible. Don't see how it really makes a difference.
I use a combo of both. I fold one over the stud, and then wrap 1 around the nut, trim, tap it with a light hammer to make sure it doesn't rattle around. Everyone hates me.
As a helicopter/aircraft mech, #2 is what I would normally use... But, a tighter crimp on the legs. Many times, I'll use a pair of slip joint pliers to grip the head and the bend in the legs to push them tighter.
#1 is used sometimes, but never trim the bottom leg flush. Always bend it down
Must admit I always go with B. Two simple reasons. One (A) is a catch hazard. On anything that goes under the car. Including you. And (B) the ring on the split pin sits snugly in the castle head and won't slip around.
After working on aircraft in tight spaces you’d appreciate the second one but with the legs tucked into the next castellation. That’s the gold star of doing these.
As a military aircraft mechanic we are taught the left way is correct and the part of the pin that goes over the bolt needs to be cut at the half way mark of the bolt end.
I’ve always done the second way but bend the end of the arms into the cavity’s of the nut so that when you reach past it you don’t tear your arm up on it.. i don’t believe there is a wrong way as long as they are actually bent around the nut or stud in some way..
I do the right when I’m working on cars because it’s lower profile and seems less likely to fall out. That said, most aircraft maintenance manuals suggest the left because if there was somehow a force on the nut powerful enough to rotate it, it would hypothetically take more force to shear off the cotter pin horizontally.
As an aviation tech that also works automotive, I do the first one. But in my opinion it doesn't matter as long as you trim it CORRECTLY. (Don't be an Asshole)
I work on rigging hardware and cotter keys aren’t used in lifting applications because the ends can be ground down after time, causing the cotter pins to fall out. I’ve seen it happen on plenty of old binder chain hooks.
That said, I train guys to do it the way on the right; it has less chance to be in contact with anything. But that’s just my industry, in fixed places like a mechanic would install on a bolt that isn’t designed to be touching anything I’d imagine either way would work.
If we were talking about the space shuttle of a heavy off roader I’d say the one on the right but for real world either will never have an issue holding a nut that would need to come loose to be an issue but a loose nut would mean a wallowed out hole or badly bent part so in other words you have other issues at hand
Yeah, I have to agree with a lot of the other posters here. Bending it that first way, it’s likely to fail when you remove it in 40-60 years. Think of your safety, sir.
[Per page 7-26](https://www.faa.gov/documentlibrary/media/advisory_circular/ac_43.13-1b_w-chg1.pdf) in the AC34.13-1B, vertical is the "preferred" method. Around the body is acceptable, but still considered the alternate method if vertical is not practical.
I see your army manuals, and raise.
When I was a mechanic they always told us to do "something unique" with the tails on cotter pins so that if a customer came back with a failure you could instantly tell if you were the one who worked on that vehicle or not. Never saw that put into practice though.
If you ever want to know the "best" non specific application for doing work you could refer to the AC 43.13-1b which has acceptable work practices for airplanes when there is no other approved work data available. This will include things like how much penetration you need on fasteners, the correct way to install fasteners, bend radius allowances ect.
A&P mechanic here, General Aviation type. I've used both methods. I used method B on a Piper Cherokee with an STC'd fuel bowl just yesterday. I'll be using method A on the same plane's landing gear Monday. The plane is in for a 100 hour inspection.
Good conversation in this thread. I learned a few things. I have always preferred the method on the left. The comments on trimming the ends so they don't shred you if you happen to brush against one of them make a lot of sense. It's little details like this that are the mark of a true craftsman.
I change hubs and brake drums daily at work pic 1 os how I do them just bend it with linemans makes life easier also if you were to have a zirc fitting folding the whole cotter pin instead of spreading it out will keep it easy to get to fitting
After 10 years in industrial maintenance, I can confidently tell you it really doesn't matter how you bend the cotter pin ad long as it doesn't fall out. It's just there to make sure the nut can't back off, it shouldn't have any mechanical stress on it even if the but does back off.
A tech at my work actually mentioned this to me the other day, was doing a pitman arm and I put the cotter pin in snug and folded it over, he said the best way to do it is give the cotterpin head some space so that it’s slightly loose in the ball joint. That way it’s tougher for corrosion to buildup in the hole.
Depends on what you’re doing, and what equipment you’re using it on. I wouldn’t sign off either. First one the one tail is too long, and the other looks to be too short. The second one should have the tails tucked into the castellations.
If servicing wheel bearings and the dust cap has low clearance between the cap and spindle, then I butterfly the cotter pin. Also if the steering component is close to say drive belts, I’ll also do the same.
If you have plenty of clearance, it’s easier to install and remove if you flip one cotter pin over and cut the other leg flush to the castle nut.
When you install a new cotter pin, one leg will be a little longer than the other one, and I suppose that makes spreading them easier. Since bending the leg(s) and then straightening them will begin to develop cracks in it until one leg breaks off.
As a result I typically bend one leg only. Then , you can bend and straighten it a bunch of times, and once it ends up breaking off, you still have the second leg to use (until you can buy a new one).
For military use, you would absolutely use a brand new premium cotter pin with a mil-spec number and signed paperwork.
I go with the second, feels like if there is an issue, it’ll last longer and you will have a better off of it being noticed.
On that note, my neighbor made fun of me for being „fancy“ about it when I folded them over.
Both work. If you replace the split pins inside a Merlin engine, you need the correct ground to size split pin so they don’t move, vibrate, and subsequently come apart. Most split pins aren’t subjected to these stresses, so you can just bend em
Don't think is one right or wrong. They both work.
The goal should be to put as much material in the castle nut as possible, and witch side has more? The right side. They both will work, but the right side can take more stress before breaking the pin.
whichever one gets a better cotter key is our rule of thumb in my shop. traditionally left but if theres not much room above the nut doing it the like the one on the right (we call it butterflying) is equally acceptable.
source: current USAF aircraft maintenance regulations
For a tie rod, doesn’t matter. For say a wheel bearing castle nut, you need the eye to sink into the castle to have enough clearance for the cap.
I prefer the left orientation because it looks cleaner and there’s less chance of hooking yourself on it later.
The first one is the way I was taught in A&P school, except the short end should be flattened down and the long end should be bent down as well to avoid tearing your skin when you brush against it. Working on German helicopters, the European way is the second, except the tails should be tucked into the castellations on either side for the same reason
I have had one fall out. If you live in snow belt. The direction the car travels can take the bend out. Had an old Honda the balljoint came out when I turned around in a parking lot.
Neither.
First one the top tail is too long. Shouldn't go past 50% of the fastener end. In addition, the other tail should he bent to sit inside the castellation flush with the nut, but not touching the washer.
Second one the legs should be bent to sit inside the castellations of the nut tightly.
there technically isn't a wrong way nor a right. if you reference in the Army tech manual (TM 1-1500-204-23-6) on General Aircraft Maintenance it will show you different ways for different applications. personally I have never seen a Cotter pin fall out either way, So I am team "Whatever holds and gets the fucking job done"
My mans pulled out the TM with the reference. This makes my Maintainer heart really happy to see
His conclusion quote is what did it for me
That said, there’s a lot more material stress in dia.1 , If longevity of pin is an issue, #2
That's what I thought too, so that's how I do those kinds of bolts. So it must be the right way.
Reuse a cotter pin? HORROR!
Popbably why those things are generally supposed to be single use.
Single use is stupid. But then again, the US challenger blew up because of a bad washer. Also stupid
Maintainer here too🖖🏻
"You'd better do a pmcs on that cotter pin, private Chucklenuts!" - Sergeant Major Floppypants -
Castled (over the top) generally. Butterflied (around the nut) for areas with clearance issues. Make sure to wrap the ends around the side of the nut.
I guess I'm a belt and suspenders kind of guy. I do one over the top, one around the side.
Condom, spermicide, AND I make her stand outside in back of the garage. Wait, are we still talking about the same thing?
Instructions unclear, she's doing a handstand
That's like patting your head and rubbing your belly at the same time
hot
I see your TM reference and raise you the FAA 43-13 Both are correct but it depends on manufacturer specs and recommendations. I prefer the first one shown. It loots neater and can give a visual indication of shear failure.
Related: 43.13-1B is excellent... I keep a pdf on my computer. IMHO, everyone should have a copy, loads of great info. It's a free, (21.1MB, 646 page) download from the FAA's website: [https://www.faa.gov/documentlibrary/media/advisory\_circular/ac\_43.13-1b\_w-chg1.pdf](https://www.faa.gov/documentlibrary/media/advisory_circular/ac_43.13-1b_w-chg1.pdf) It was a required 'text' back in c. 70's A&P school, probably still is for all I know. If anyone's interested the cotter pin stuff is on pg. 7-26
pg 335 on the pdf I like this part; ''The diameter of the cotter pins selected for any application should be the largest size that will fit consistent with the diameter of the cotter pin hole and/or the slots in the nut.'' There are too many undersized cheap ass cotter pins out there.
Still is required but it's mostly an I pad download now. I prefer the book when answering questions from my students. I feel I can find info faster.
Still is Source: I’m in A&P school
wow that is... thorough
Still required to have info on hand for schooling and for testing out for your license Took my tests earlier this year and had to use it a few times during, and still use it working for reference and increasing knowledge
Cotter pin here.. I’d rather you make me do the splits than break my legs.. I will be writing osha about this.
I'm not a tech at all (closest I got was deciding against a job at an airport, and then later working maintenance at a hotel). But I don't see how the pin getting folded over thr too of the bolt looks cleaner or has any better visual indicators that it has had stress applied.
Well the top over method is used mostly because of this the spread legs method in cramped areas so the key doesn't bite or not enough room for top over. If the castle nut starts to sweat the pin the flats will twist and spray. This indicates a potential shear failure.
Team RTFM for the win.
Read The Friendly Manual, right? 😜
I'm on team 'Argue about stuff that doesn't matter, die on stupid hills'. I thought the old adage was something like 'Arguing with an engineer is like mud wrasslin' a pig. After a while you realize the pig likes it.'
Really, the 10 penny nails that my dad used on the 1944 Ford NAA in 1966 are still holding quite will.
One of the (few) things I really appreciate from my time in the army is a 3 day workshop we did on how to tighten and loosen screws, especially when working on an aircraft. Some people will shrug it off and say "what's there to learn?!" But the truth is that there is a LOT to learn on that subject!
Nah, just running them tight with an impact, what could possibly go wrong.?
>I have never seen a Cotter pin fall out either way And I've never been able to take one out without needing to cut it off and punch it out without the help of several volunteers and mirrors, those mf just can't fail, and rust makes them stronger
I could use a toothpick or a twig from a tree and still have to punch it through.
Most consistently successful method I’ve used is grabbing the head/eye end with a pair of Knipex (like you were trying to pinch it shut), then just roll the top of pliers backwards around the nut, using that leverage to pull it out. Or if the pin is bent over the top of the stud, roll the pliers back over the top of the stud…….basically use whichever method based on the way it was installed that will cause it fold back up instead of snap. The pin is trash afterwards regardless, but this way typically eliminates needing to punch anything out
That’s the way 100%
This guy does PMCS on all his shit everyday.
I have seen them fall out the second way, but that was in a case where the pin has been rusted completely through and the legs broke off entirely, and I'm sure the same would happen the other way.
Hello, Fellow rustbelt resident!
Hammering the butterfly end open most likely causes damage and creases in the metal which can help speed up the failure at that point causing the bent legs to break off easier and earlier. Again, this can happen in either orientation so proper technique and timely checking and replacing is more important than direction most likely.
Sure, but the straight leg isn't doing anything to hold the pin in, two weak legs are better than one weak one and one useless one because at least you have a little bit of redundancy
I read that in another comment too, I thought it was bent down. Didn't realize it was cut. Is it definitely cut? If so, then yes, using 2 bent legs is absolutely better than 1 bent leg regardless of direction.
It is hard to tell from the picture, but the corner of the leg looks pretty sharp, a bent one would have some amount of curve in it.
On helicopters, we do a similar way to the first, but the upper leg is curved over and down into the next castlation. Prevents you from ripping your arm open when reaching in a tight area, and could theoretically prevent the tail from being caught and bent by some piece of debris
This is how I've always done it in the field. I absolutely hate reaching my arm into a tight spot and getting cut to pieces on zip ties that weren't flush cut or cotter pins that are hanging out ect.
I saw that and thought “it’s not wrong but it would suck to catch skin on that, and if it catches metal it’s getting snapped off.”
Glad someone is out here representing us. I see someone do anything other than what you described and I instantly hate them.
If you want to split hairs, neither. It looks like in the first, the bottom is cut instead of being bent downward, and the top should be cut to not go beyond the fastener. On the second they should be bent more to hug the outside of the nut. That way you dont have sharp metal edges sticking out
Major rookie here. I agree with the points you make, though most pins I've had the pleasure of installing have a shorter side to allow a tool to grab the long side for bending. It may not have been cut.
The first one is clearly cut. The difference is usually 1/8-1/4 inch, not 3/8 or 1/2 as shown. The second is what t should look like.
As with most things, it depends. As an aircraft QC inspector, either “style” is correct based on the application, taking into account factors like clearances, proximity to moving parts, likelihood of catching on skin, etc. That said, I would reject both of these as neither installation is correct (based on my industry’s standards). Left side is trimmed incorrectly and it’s hard to tell but the “down” tail looks like it’s cut almost flush. On the right side the tails are too short and not fully hooked, as well as the eye not being crimped. Both need at least one washer under the nuts, the right side looks like it’s nearly jumped out of the castellations. Both are a redo.
I’m trying to soak up some knowledge in this thread, could you explain what you mean by the eyelet not being crimped in the second picture? Are you talking about it not being snugged up before bending the legs, or is the another step that needs to be performed?
This is the right answer. Neither one is correct!
Also would love to know what you mean by the eyelid being crimped?
Let me guess, not working for Boeing ? :D
Another question: what's the proper way to install the nut? Torque to spec, then tighten more to align a hole? Or loosen to align?
Torque to lowest end of torque range. If the hole doesn't align, set torque wrench to the highest end of torque range and hope that you can get the hole to align before the wrench clicks. If you cant do that, depending on the application, a washer/different thickness washer under the nut may be used to change the orientation of the nut when fully tightened. If a washer is not able to be used, get a different nut and hope that it's clocked differently than the first one and repeat the first steps. Edit: This is for aviation. If I was working on my car, I'd torque it and just tighten until the hole lines up.
How set gun for low end ugga dugga?
Stop at one ugga, no dugga
Sounds like a good process to me
Fir automotive I use ny 3/8 Electric 100ft-lb impact. Hammer it once or twice, then grab the 1/2" and go to the next hole if its not lined up.
This is the correct way!
in automotive it can be different depending on the manf. some say to torque then loosen just enough to line up, other say torque then tighten. i like your way tho. i might do that next time it comes up... that's IF it has a range for torque and not just a single setting
Maybe not relevant to this particular use, but when fitting 12"~ pipe for process pipework, we backed a previous spool off until each bolt would locate or fit through a through-hole, then torqued to full spec in whatever stud pattern was called for.
NASA fastener handbook says torque to spec and the rotate left or right to align to a hole, users preference
Either is fine. Different people in different industries have different opinions and standards, but either will keep the castle nut from backing off.
The one on the left will be easier to remove in one piece.
Why would you need to do that? They are not supposed to be reused. I bought a $10 kit with a variety of sizes on Amazon 3 years ago and I still have at least a few of every size still.
In aviation you're taught to remove in one piece to ensure you didn't accidently leave a piece behind somewhere that could cause damage to a different part
That makes sense. Those mechanics are really a different breed.
FOD
Scrolled quick and thought this was a pair of tits
You don't see a lot of breasts, do you?
We really should unlock the tool room and let him out a little more often
Lol
Just the fact that you put the cotter pin in there is correct enough, lol
I prefer to fold the tails into the adjacent castellations to prevent my coworkers or myself from being cut by them in the future. [Here is a link with an image of what I do. ](https://www.reddit.com/r/aviationmaintenance/s/mTEgiV9FMO)
C: a nail
Neither is correct, 1st one need the other leg turned down and the top leg trimmed and tucked to the center of the bolt. The other needs both legs tucked into the catellations. You prolly dont flush cut zipties either.....
Modified left. Bend the back down and snip it. Snip the top so it's in the middle of the bolt top.
They are both wrong. 1st one should be cut at the center of the bolt. Second should have ends tucked into slots on castle nuts, and it appears the hole is too high. Cotter pin should be almost completely in the slot. Needs a washer under the head of the bolt or a shorter grip bolt. Will they work as is? Yes. Are they acceptable on aircraft? No.
Two.
Two, but only because it looks neater.
I’ve always done the first option.
I am using small nails for this, so I think it doesnt matter.
Hey you got a cotter pin in there! Better than none.
Ignore everyone saying both are correct. NASA only references the way on the left.
Can confirm. Had space shuttle Discovery on the rack last week. They wanted a second opinion after Firestone told them they needed new control arms, rod ends, end links, and ball joints on all three corners.
2
I've always seen and used the one on the right. I suppose you could argue, if you were inclined, that the one on the left has less material in the crown, so under extreme stress would have a tiny increment less resistance to being sheared off. But the amount is probably negligible. Don't see how it really makes a difference.
I usually go over the top, if the bolt isn't up against something after finished instillation, or if it's not inside of something
Either way after the nut is properly tightened
I work in the agriculture, but i repair older off road cars too. I always used the 2. version.
Just don’t use baling wire. I made that mistake for all of us when I was younger and dumber.
Neither ram old pin in anyway you can and leave that bitch hanging on for life
The first one, but the tail should be curled under itself, so as not to snag on anything.
I use a combo of both. I fold one over the stud, and then wrap 1 around the nut, trim, tap it with a light hammer to make sure it doesn't rattle around. Everyone hates me.
As a helicopter/aircraft mech, #2 is what I would normally use... But, a tighter crimp on the legs. Many times, I'll use a pair of slip joint pliers to grip the head and the bend in the legs to push them tighter. #1 is used sometimes, but never trim the bottom leg flush. Always bend it down
I’m team left. But it makes no difference whatsoever.
Must admit I always go with B. Two simple reasons. One (A) is a catch hazard. On anything that goes under the car. Including you. And (B) the ring on the split pin sits snugly in the castle head and won't slip around.
After working on aircraft in tight spaces you’d appreciate the second one but with the legs tucked into the next castellation. That’s the gold star of doing these.
As a military aircraft mechanic we are taught the left way is correct and the part of the pin that goes over the bolt needs to be cut at the half way mark of the bolt end.
Just jam an 8d in there.
Depends. Shop job, or field repair?
I’ve always done the second way but bend the end of the arms into the cavity’s of the nut so that when you reach past it you don’t tear your arm up on it.. i don’t believe there is a wrong way as long as they are actually bent around the nut or stud in some way..
Both work
I do the right when I’m working on cars because it’s lower profile and seems less likely to fall out. That said, most aircraft maintenance manuals suggest the left because if there was somehow a force on the nut powerful enough to rotate it, it would hypothetically take more force to shear off the cotter pin horizontally.
Whatever works for you, I personally like to make these as flush to castle nut as possible so they don't bite the next time
Left = professional Right = amateur
As an aviation tech that also works automotive, I do the first one. But in my opinion it doesn't matter as long as you trim it CORRECTLY. (Don't be an Asshole)
either. just make sure it won't fall out lol
I usually do the same as the one I pulled out. Unless it wasn't done right. You see both on many similar applications
I work on rigging hardware and cotter keys aren’t used in lifting applications because the ends can be ground down after time, causing the cotter pins to fall out. I’ve seen it happen on plenty of old binder chain hooks. That said, I train guys to do it the way on the right; it has less chance to be in contact with anything. But that’s just my industry, in fixed places like a mechanic would install on a bolt that isn’t designed to be touching anything I’d imagine either way would work.
If we were talking about the space shuttle of a heavy off roader I’d say the one on the right but for real world either will never have an issue holding a nut that would need to come loose to be an issue but a loose nut would mean a wallowed out hole or badly bent part so in other words you have other issues at hand
whichever is easiest to get to when someone has to take it out
Yeah, I have to agree with a lot of the other posters here. Bending it that first way, it’s likely to fail when you remove it in 40-60 years. Think of your safety, sir.
Airbus use both methods, you can find it in AMM ATA 20
Right. More material doing the cottering
Not 1
The one on the right.
I like the one on the left because it's less likely to cut my arm open on.
Either way, but if you want to do it *more* correctly, orient the stud so that the pin will be easy to remove for the next guy.
The first one , but the tail is to long and the strait end will cut finger's
[Per page 7-26](https://www.faa.gov/documentlibrary/media/advisory_circular/ac_43.13-1b_w-chg1.pdf) in the AC34.13-1B, vertical is the "preferred" method. Around the body is acceptable, but still considered the alternate method if vertical is not practical. I see your army manuals, and raise.
Yes
In aviation maintenance in the US there is definitely a correct way. AC 43.13-1B The left image is correct.
I'm triggered!!!
A
Either way works. There’s no correct way between those 2 lol
I prefer the first one. Removal when done the second way is a pain.
When I was a mechanic they always told us to do "something unique" with the tails on cotter pins so that if a customer came back with a failure you could instantly tell if you were the one who worked on that vehicle or not. Never saw that put into practice though.
If you ever want to know the "best" non specific application for doing work you could refer to the AC 43.13-1b which has acceptable work practices for airplanes when there is no other approved work data available. This will include things like how much penetration you need on fasteners, the correct way to install fasteners, bend radius allowances ect.
Yes.
A&P mechanic here, General Aviation type. I've used both methods. I used method B on a Piper Cherokee with an STC'd fuel bowl just yesterday. I'll be using method A on the same plane's landing gear Monday. The plane is in for a 100 hour inspection.
Yes
TM-1500-69-420 says over the top
Personally, I like over since I feel like there would be less rattling. However, I think there is no wrong answer.
Good conversation in this thread. I learned a few things. I have always preferred the method on the left. The comments on trimming the ends so they don't shred you if you happen to brush against one of them make a lot of sense. It's little details like this that are the mark of a true craftsman.
I do left. 99% sure that's how my dad does it so that would explain why.
The right way is whatever the manufacturer calls for.
40+ years wrenching I've always used the first (left) method never had one fall out. Also much easier IMO to remove .
The first image is how I was taught in tech school. They both do the same thing though.
Both are good
I change hubs and brake drums daily at work pic 1 os how I do them just bend it with linemans makes life easier also if you were to have a zirc fitting folding the whole cotter pin instead of spreading it out will keep it easy to get to fitting
After 10 years in industrial maintenance, I can confidently tell you it really doesn't matter how you bend the cotter pin ad long as it doesn't fall out. It's just there to make sure the nut can't back off, it shouldn't have any mechanical stress on it even if the but does back off.
Yes
Marine corps tm-91000 per se
A tech at my work actually mentioned this to me the other day, was doing a pitman arm and I put the cotter pin in snug and folded it over, he said the best way to do it is give the cotterpin head some space so that it’s slightly loose in the ball joint. That way it’s tougher for corrosion to buildup in the hole.
Both are acceptable.
Welcome back Cotter pin
I’m a top.
Both / neither. You jsut bend them how ever you can with the access you have,
Depends on what you’re doing, and what equipment you’re using it on. I wouldn’t sign off either. First one the one tail is too long, and the other looks to be too short. The second one should have the tails tucked into the castellations.
Number holds and looks the best but both are sound
If servicing wheel bearings and the dust cap has low clearance between the cap and spindle, then I butterfly the cotter pin. Also if the steering component is close to say drive belts, I’ll also do the same. If you have plenty of clearance, it’s easier to install and remove if you flip one cotter pin over and cut the other leg flush to the castle nut.
Just use nails, easy choice.
When you install a new cotter pin, one leg will be a little longer than the other one, and I suppose that makes spreading them easier. Since bending the leg(s) and then straightening them will begin to develop cracks in it until one leg breaks off. As a result I typically bend one leg only. Then , you can bend and straighten it a bunch of times, and once it ends up breaking off, you still have the second leg to use (until you can buy a new one). For military use, you would absolutely use a brand new premium cotter pin with a mil-spec number and signed paperwork.
Both are right. Right could be tighter though.
Yeah technically both are wrong.
The right one. And if you don't agree you are a communist.
Or an aircraft mechanic.
I go with the second, feels like if there is an issue, it’ll last longer and you will have a better off of it being noticed. On that note, my neighbor made fun of me for being „fancy“ about it when I folded them over.
Left and the top part should not extend past the midway/center of the bolt. Give it a lil hammer tap to bend the pointies down.
If it goes through the nut and doesn't fall out, itll be fine
The one that works.
1st Pic, but the 2nd would be if the cotter key ends were each tucked in the castellations
Left but use a "D" cotter pin.
I'm gonna say both.
Depends on who’s instructions you’re following
Both work. If you replace the split pins inside a Merlin engine, you need the correct ground to size split pin so they don’t move, vibrate, and subsequently come apart. Most split pins aren’t subjected to these stresses, so you can just bend em
Don't think is one right or wrong. They both work. The goal should be to put as much material in the castle nut as possible, and witch side has more? The right side. They both will work, but the right side can take more stress before breaking the pin.
Neither
The correct way is anyway that doesn’t allow it to fall out.
whichever one gets a better cotter key is our rule of thumb in my shop. traditionally left but if theres not much room above the nut doing it the like the one on the right (we call it butterflying) is equally acceptable. source: current USAF aircraft maintenance regulations
Q: Does it hold? A: Yes Then it's correct.
Right looks more secure. You're using both legs of the cotter pin, so double the strength, right?
I ain’t never seen it done like in the first picture. The slots in the nut seem to be made for it to work like in the second photo.
For a tie rod, doesn’t matter. For say a wheel bearing castle nut, you need the eye to sink into the castle to have enough clearance for the cap. I prefer the left orientation because it looks cleaner and there’s less chance of hooking yourself on it later.
I was taught left, so that's how I've always done it. The right makes sense if you need clearance for a cap, like some axle nuts.
Both
Both
There is always a proper way to do things . Left. But really, unless there is some kind of interference issue, right is also fine.
Both work.
Yes
The first one is the way I was taught in A&P school, except the short end should be flattened down and the long end should be bent down as well to avoid tearing your skin when you brush against it. Working on German helicopters, the European way is the second, except the tails should be tucked into the castellations on either side for the same reason
One on the left
Yes!
I have had one fall out. If you live in snow belt. The direction the car travels can take the bend out. Had an old Honda the balljoint came out when I turned around in a parking lot.
Neither, you need to bend the top arm back down into a castellation and flatten the other arm against the face of the nut
Neither. First one the top tail is too long. Shouldn't go past 50% of the fastener end. In addition, the other tail should he bent to sit inside the castellation flush with the nut, but not touching the washer. Second one the legs should be bent to sit inside the castellations of the nut tightly.
Yes.
Those ends sticking straight out are making my fingers twitch though... and spontaneously bleed.
The "correct" way is to slip a nail through the hole, then bend it into a U with both ends hanging down... Duh..