Proper Method to Upset (Bend) a Cotter Pin

Would this be how it is done?

https://www.youtube.com/watch?v=BqdPE7ddib0

...I've seen cotter pins mangled in many ways, as in the photo here.

Photo? What photo?

Ahhh.

I disabled my AdBlocker software and the photo appeared.

Hmmmm. I see there can be a downside to the Adblocker ad-ons in Firefox.

Nowadays I just use the nuts with the nylon insert....If a cotter pin is required as well, like on an aircraft, I just bend them as you have pictured, one leg up, one leg down...or a castellated nut which can be used with wire or cotter pin....or a combination castellated nut with insert either fiber or nylon....some nuts have holes in them for wiring ....

Lyn do you remember the post I had on the cotter pin and castleated nut. I agree with the YouTube video where you insert the cotter pin as far as possible and then bend one leg over the end of the bolt and the other leg down onto the side of the nut. To tell you the truth, no one had ever taught me how to do it properly. The only time I was shown was on a dune buggy and it was done the improper way because it was easier to fix in the middle of the desert. My post on CR4 and all of the responses helped me to figure out how to do it properly which is the way the video shows. The reason I installed it that way was because another component would hit the leg of the cotter pin when rotated and interfere with the proper operation of the device. (The device is a fall arrest system that we manufacture and was engineered by a different company) I believe that the proper installation is the one that works for the individual situation. Lyn, from all the communication we have had, I respect your opinion because you immediately drive for the most logical answer and don't put up with any B.S. Thank you

What is the correct way insert a cork in one's butt, in order to be so retentive?

Hint: after insertion, drive a cotter pin through it.

Hahahahahahaha!

LOL!!!

That brings up the question of type of lubrication and amount of torque or insertion pressure to achieve a proper seal.

Most likely the best way to upset a cotter pin, or anybody for that matter, well almost anybody, not that there's anything wrong with that.

Rolls Royce bends both the ends of the cotter pin over the bolt end.

Gajanan Phadte

What is it in the photo? It looks to me like the cotter pin is there to stop a part sliding off the inner shaft longitudinally. If so, and it's a moving device, without knowing full details it doesn't seem a very good idea.

Perhaps best practice for bending in this situation is different from e.g. a castellated nut.

Interesting comment "to bend cotter pins and use tie wire to indicate bolt loosening. (not to lock them in place)". I've always assumed main function is to keep nuts tight. After all they're often used where failure would be serious and inspection difficult e.g. engine big-ends. Nobody's going to dismantle an engine just to check these nuts are tight.

As other have said that tie wire is to keep fasteners tight. In most applications that I have seen it used. It's function is more to keep the bolt if it came loose from falling out. Like in a gear box where if it fell out. It could get jammed in the gears and cause more damage.

As kids, with a great huge, paved hill nearby, the import of a properly applied bent nail for retention of absconded tricycle and red wagon wheels onto the axels of home built gravity powered "go carts" or soap box cars became evident with the loss of control for one downhill racer by the name of Iggy Favor, causing collision with retianment wall surrounding the sludge pond (Location: sewerage treatment plant) and the ejection of Iggy into said sludge pond. We as a group, avoided Iggy for the rest of that day.

Not sure how else the cotter pin could be installed in the photo... no enough room to rotate 90-degrees. Maybe a little over-bent though.

But, with a Castle Nut, the pin would be rotated so that the head fits in the slot of the nut and one pin is bent up and over the shaft and the other is bent down and trimmed. At least that's how Grandpa taught me.

As for Wire-Tie... yeah I can't tell you how many times I've heard/seen people think it was to keep the bolt tight... safety wire is not going to prevent a bolt from loosing clamping force.

If properly installed, bolt-to-bolt, bolt-to-screw or connector collar, the tension provided by the simultaneous pulling and twisting should pull the fastener in the direction that would tighten. If there is any lack of tension, it would be rejected by QC. Wether or not it would prevent loosening, I don't know, all I know is, every bolt, nut or electrical connector, except for castellated nuts with cotter pins, on the aircraft I worked on, used safety wire. The mechs ran out of the special castellated nuts for the exhaust headers, and were ordered to use nylock nuts as a temporary solution.The pilots were outraged but told to shut up and fly anyway. The mechs double up on the nuts as a precaution but had a hard time getting the nuts off later due to the melted nylon. Maybe melted nylock nuts could be marketed?

GA

Thats how I was taught as well, you end up with one short leg poking out but still in line so to say, and one leg bent back over the end of the bolt.

Never had one get loose.....no engines damaged.....

I have a picture here of a Cotter pin about "half" installed, but using the method I generally use. He has just cut the shorter leg, he now needs to "dress" the longer leg properly.

It was explained to me that the reason was that the nut would have to turn enough to cut BOTH legs through, before a piece of the cotter pin would be "let loose" in an engine.

With some other methods with the pin at 90° to this method, only "half" of the pin will be needed to be cut through and a "leg" would be released.....never seen that though....

By the way.the "dimple" in the end of the bolt was told to me that the longer leg of the Cotter pin must be lightly driven into, but I forget the reason for that....I also saw it done that way on many online photos too.....its probably to restrict movement from vibration at a guess....

The only point I see here as possibly being wrong is that the nut is a little too far down the thread for the hole. A washer is needed to allow the correct tightening of the nut and to put the hole better in line with the nut openings....or it may just appear so optically......

Finding the right washer may be a problem of course on a Sunday.....!!

"By the way. the "dimple" in the end of the bolt was told to me that the longer leg of the Cotter pin must be lightly driven into, but I forget the reason for that...."

Reason I was told was to reduce the probability of centrifugal forces trying to straighten out the cotter pin.

That makes sense for things that turn and fully believable.

I have no recollection anymore of what I was told (if anything!), your explanation is the best I have seen up to now, thanks.

The cotter pin in the assembly pictured does not rotate.

I agree that as a long as a cotter pin does not come out of its perch, how it is bent is not that important.

However, the purpose of safety/tie wire may open to debate. At least in my mind.

That too, may depend on the specific application, intended purpose of the wire.

The wheel bearing nut should be tightened until "Monkey Tight" then the cotter pin inserted and then staked, only then does one discover that the tapered roller bearings are completely locked up, and should have been tightened only to the point of take-up and no further, which is the reason the pin is required in the first place. The dimple on the end of the shaft might be the center used for machining operations, maybe not.....

While in high school I worked in a tire shop doing front end alignment and brake jobs...the 'spec' we used for front wheel bearing nuts was tighten to 25ftlbs and back off 1/8 turn to set clearance for grease film, then key through nearest hole, which explains the multiple holes in the spindle.

Older vehicles used ball bearings instead of tapered roller.These had to be tightened as you said.

The "newer"(relative term) bearings were tightened to eliminate all hysteresis,then staked with a thin locking collar to a slot in axle.

The center hole is for the machining operation during manufacture in this case,but it has other uses in some cases to provide an anchor point for pulling press-fit bearings.

Even this method has probably been superceded by newer technology,as it has been many years since I had to work on front wheel bearings.

The one source I would consider practically unimpeachable for cotter key installation and safety wire is the FAA method referenced in my previous links.

I knew that, just trying to add some levity. I am surprised that no one has asked what "Monkey Tight" means.

Isn't that what monkey wrenches are for??

• Grease Monkey?
• Greasy Monkey?
• Elbow grease?
• Monkey with a greasy elbow?
• 

Yes,there really is a monkey wrench.

I have a couple in my tool box.

Here is a link with images:

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

All the wheel bearings I have adjusted (not all are adjustable!!), there was a procedure to achieve the correct setup.

One such procedure was to torque up to a certain value.

Spin wheel.

Loosen.

Torque up to a newer, but lower value.

Insert cotter pin and secure.

I have used several different procedures over the years, The car manufacturer sets "how".

I don't myself believe its anything to do with machining of the part, just look at the shape of the hole for example and bolts are usually made on automatic "center-less" lathe type equipment as well.....they have no need of such a hole....

Look at most bolts and you will not find a center "dimple" at all on either end....

I remember the method you described on certain VW's from the '60's and '70's,and you are correct,procedures vary from manf to manf.

As for the center hole,it is critical that both inner and outer bearings be on the exact same plane,and is probably used for centerline reference spec on spindle.

They will not add anything to the process that does not serve a purpose,not even a dimple.

The other holes may not be as critical.

Mass produced bolts are made with grooved rollers,and do not need a center hole.

The rollers do not remove any material,and the cold working increases the strength and hardness of the threads.

Thanks,

About what I expected.

Unredundant Yes, I used to use wire twist pliers every day. We mounted the boom head on the cherry pickers to the main frame with 16 1"-8 TPI bolts, all tie wired together. Not for retention, of course, just as a visual indicator that a bolt was loose.

Original_Macgyver I do remember our discussion about castellated nuts. I still agree that cotter pins is the only sure and safe solution.

As for cotter pins, I don't know that there is a correct way for every application.

Where I worked, we bent the long leg to about 45° and left the short leg straight. That's all it takes to secure the pin so that it won't come out. We never cut pins to length, we used the correct size. Is that the right, correct method? I don't know. It's what we did and never had a failure.

Codemaster, the photo has no relevance, it's just to show a bent pin.

ozzb, tie/safety wire properly installed/tensioned will break as soon as the bolt head turns. After that, there is nothing to retain the fastener.

Many here share your position that wire will retain a loose bolt. I don't know how it could.

Maybe I'm wrong.

The video shows a guy (or girl with man hands) using a ball pean hammer to do the job, they cut out the part where the threads get bunged up by an errant blow.

(No smiley face, or pasting of image allowed with IPad).

Isn't that part of the off topic knob on an enigma machine? The longer leg indicates direction of rotation. Score one for topical application only.

I guess this is a reply to my cotter pin question from months ago. After careful inspection and months of use, the cotter pin application I used has survived the very hard use on a machine that vibrates 24/7 and is on a life safety device. I truly appreciate the time everyone took to assist in my dilemma. Not one of the cotter pin installations have failed or even loosened. I agree that every application requires a unique solution and sometimes it takes the opinion of a group of knowledgeable people to solve a problem. I enjoy facing a challenge, it actually makes me work harder to find the best solution. My coworkers call me anal but I will never shortcut when it comes to a persons life. Thanks again.

lol, why don't you trying googleing it:

http://www.ehow.com/how_7492535_properly-install-cotter-pin.html

http://en.wikipedia.org/wiki/Safety_wire

No offense. but I have found eHow to be worse than useless.

99% of the articles there are written by people who HAVE NEVER performed the tasks they are telling you how to do.

They get paid to write these things and most of them just sit at their PC and copy some other source.

I've already commented on safety/tie wire.

But, everyone has an opinion, and here they are usually different.

Lyn, To perpetuate this forum, I searched for "cotter pin grades". I got nowhere. I think my search engine has thrown a rod.

Either you didn't bend the cotter pin properly, or your safety wire broke.

I was always taught that a cotter pin is a round pin with a thread and nut on one end and a taper running up the side. These are used to fit the peddle crank to the cross shaft on a bike. As you tighten the nut it pulls the tapered pin in and locks the crank to the shaft. The "cotter pins" you are talking about I was always told were called split pins when I was an apprentice and was given a rollicking if I called them cotter pins.

From Wikipedia, the free encyclopedia
Cotter pin may refer to:
In U.S. usage:
Split pin, a metal fastener with two tines that are bent during installation used to fasten metal together, like with a staple or rivet
Hairpin cotter pin, more commonly known as an "R-clip"
Bowtie cotter pin, a vibration-proof type of R-clip that is shaped like a bowtie
Circle cotter, a ring-shaped cotter pin
In British usage:
Cotter (pin), in mechanical engineering a pin or wedge passing through a hole to fix parts tightly together
This usage difference is often a cause of confusion when companies of both countries work together.
The original design for the cotter pin was designed by Dr. Rudolf Cotter in 1834. The original design employed a bolt with a hole drilled through and shank of metal placed within the hole.

Welcome back, Cotter!

Exactly. It depends where you are in the world. It doesn't mean somebody's right and somebody else is wrong.

It would appear that the 'proper method' depends on WHAT is being fastened, and why.

the the photo on the original post, the cotter pin is going through a solid shaft, to keep a bushing from sliding off, it is installed with the flat face of the 'eye' against the bushing, so the cotter pin cannot rotate.

For the slotted nuts, the cotter pin is installed with the flat face of the eye in a plane parallel to the axis of the bolt.

If you look at this while taking into consideration the oval shape of the wire used to make the pin, you see a clear pattern: The 'wide dimension' of the wire is the dimension taking the load, the linear load of the bushing trying to slip off in the first pic, the torsion of the nut trying to loosen in the second pic. So, barring specific regulations, it would appear to be a rule of thumb that "the force you're trying to stop runs 'through' the eyehole."

There may be exceptions, such as using a cotter pin to secure a clevis pin, where the clevis can slide within it's mount, and therefore, the cotter pin will not always be in the right angle, especially if the clevis pin is frequently removed/reinserted in the field, but those situations should be pretty obvious while setting up, and one could still make an attempt to keep the cotter pin from rotating by bending the tines up against the clevis pin. Also, from what I've seen of clevis pin connections, when the pin is under load, it does not slide, so the cotter pin is just to keep the clevis from falling out when loose.

Finally, let us not forget the shear pin, prevailent on large numbers of small outboard motors (except those brands with the rubber slip clutch). The importance of keep a supply of spares becomes evident in the rocky northern lakes, where large boulders loom just below the surface, waiting for the nimrod, ready to produce that awful crunch and leap of the motor. AW #%£€, NOT AGAIN! The last spare is the one that falls in, due to failure to perform replacement over dry land. It falls in near the island used to make the Hamms Beer commercials, WTFOITMON.

Always carry a couple of coat hangers and pair of pliers with wire cutter just in case.

Many shear pins can be cut from one coat hanger.

On a very long fishing day, the brass finger from one's belt can be used as a last resort.

I cannot interpret the meaning of your acronym:WTFOITMON.

I have some ideas,but not certain.

Must be a local thing.

Please enlighten us non-locals if you will.

Way the f..k out in the middle of nowhere.

Tanks!

I will add that to my redneck acronymn dictionary.

Cute and right!!!

Great and very interesting video, though I have never actually seen them before on anything..... but very impressive indeed.

Thanks.

HiTekRedNek, Those are some nice resource's for those who need to know the proper way of doing things,

You know God created mechanics because engineers needed hero's too,

My Bible when in need of advise.

AC 43.13-1B, Page 7-26 Par 7-127

Under FAA Manuals

Fixit

The correct way to upset a cotter pin is to give it a harsh tongue-lashing. The ensuing psychological problems will cause the cotter pin to get all bent out of shape, which is exactly what you want.

Pretty good for an AP.

Are you a screen writer for a comedy show? I seem to recognize the humor!

No, but I wonder whom I might resemble!

The invisible poster.

So... not Screen Writer... but rather a Ghost Writer ;-)

Be very careful not to upset the cotter key too much.

Remember,they have a split personailty,and could fly off the handle(shaft,etc.) without warning.

LOL!!

Really nice video. Thanks for sharing!