Cotter Pins

I've never heard of graded cotterpins, they may be out there somewhere... Suspect the hair pin style would be a stronger spring type steel though.
 
This is an interesting post. I have noted that cotter pins made in the 'far East' are not nearly as stiff as those of uncertain age we moved out of the old shop when we were bought out 8 years ago.
 
I looked at Grainger, Fastenal and McMaster-Carr and everything I saw looked to be the soft cotter pins like they have everywhere else. I ended up ordering a few sizes from Aircraft Spruce and they are tougher than the Far East cotter pins.
J.I.Case used some cotter pins that are called "case hardened" in the parts books. They are tougher than the aircraft cotter pins. I don't know a lot about case hardening but might try it on some cotter pins and a few other things to see what happens
 
"Grade 5" refers primarily to the tensile strength of the steel a fastener is made from. Cotter pins are by necessity soft, so they have a very low tensile strength. If you have a problem with cotter pins breaking, you're probably using them in the wrong application.

If you use mil-spec cotter pins, they are at least manufactured to a specification, which is of course more than you can say about the hardware-store variety. Wicks and Aircraft Spruce both carry MS24665 cotter pins.
 
If you find a place let me know. I was told if you use the cheaper ones in pto or torque clutches they will wear out quicker from the vibration.
 
So the application is to secure the nut on my bush hog pan. I had to put a new gear box on. I have run out of threads when tighting up the nut on the pan. So I have about half a hole to use. I put in a smaller (diameter ) cotter pin. I have ran it about three hours so far with no problems. But I was hoping to get a stronger pin.
 
Case hardened cotter pins have a hardened surface so that they wear well, but have a soft center so that they will still bend. Another possible source for these pins is from roller chain suppliers. They use only hardened pins for the master links on large roller chain.
 
I've had trouble with cotter pins so I started using safety wire. Doesn't look as good but sure works better
 
We used safety wire on Tank engines. We twisted it by hand. The Air Force has tool for doing the twisting and it's fast too. Some of them called it lacing wire. Hal
 

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