Cotter Pin Size

[Scott_F]

Is a -132 cotter pin acceptable for use with AN4 bolts, or is a -208 size required? The ACS AN3/AN4 hardware kit I ordered only came with -132 size pins.

Yesterday was a really bad day in the shop, hoping for some recovery today....

V/r,
-s

[Greg Arehart]

Scott,

I'm not an engineer, but my take is that if the pin fits (i.e., is not grossly undersized, it should be ok. The fundamental point of these pins is to keep the nut from rotating, and there is fairly minimal stress on the actual pin itself. I've used safety wire in place of pins in a temporary installation when I didn't have a cotter pin handy.

If I'm wrong and there's some specific reason for the matching of a pin to hardware, I hope somebody will correct me here.

greg

[az_gila]

...that you should use the largest size that will fit consistent with the hole in the bolt and the slot in the nut (section 7-127)

But, in the case you mention, a -208 might or might not fit.

A 5/64 (the -208) cotter pin is a nominal size of 0.078 inches.

The hole in the AN4 bolt is 0.076 to 0.086.

Given the range of tolerances involved, the -132 cotter pin (0.063) would be a consistent fit, whereas the 5/64 pin might, or might not fit. It also might be also affected by the "off center" tolerance of 0.010, so even if the larger cotter pin did fit, it might not line up with the nut slots.

In your example, I would say the -132 would be correct....

UPDATE - the newer MS24665F specification which replaced the older AN380 cotter pin specification says to not use the 5/64 size pins for new designs.

http://www.everyspec.com/MS+Specs/MS...65F.007213.PDF

The 1/16 pins are recommended by this MS specification for a 0.078 size hole, so definitely, the -132 pin is the correct one to use....

[Scott_F]

Thanks Greg and Gil. My copy of the "bible" is on my computer at work. I'll use the -132 - partly because of the spec Gil referenced, but to be honest, mostly because I don't think there's any way the one, single -208 I found in my hardware collection is going to fit. I could barely get it through the bolt hole with no nut on, and wrestling it into the mounted flap actuator bolt inside that 766 channel seems darn near impossible. 1/16th it is!

Thanks for the help,

-s