cotter pin size

Leroy

Well-known Member
Why are cotter pins listed for one size and actually a smaller size. Working on a hay rake and factory size cotter pin measures 5/16", Had new unopend box of assorted pins with one listed as 5/16" but it only measures 1/4", the 1/4" listed size is actually only about 7/32". places the book calls for 1/8" pin what you buy is so loose in the hole you can't see how it can hold up to use without breaking. What do you do to get the actuall size the parts book calls for and fits? I did actually find some 3'16" one place that did fit the 3/16" hole but that was the biggest they carry. I at times need a 3/8" pin but I have been able so far to subistute a 3/8" bolt but cannot always do that due to the head and nut. That new 5/16" is just way loose in the hole that the old 5/16" fit correctly in.
 
news to me as i drill bolts regularly at work for over head equipment and when i drill a 1/8 hole the 1/8 cotter pin goes in snug. same with the other sizes. we buy them by the box with the actual size in each box, so not sure what u mean , unless they are packaged wrong.
 
Hello Leroy,

Cotter pin sizes are the same as the hole they fit into. The land of almost right is wrong! Try Fastenol, they list them is proper size. 3/8 by 3 in,

Guido.
 
Interesting.....I think you have a lot of good answers on here; I was just reading your post; are they made in "China" ? Not trying to be rude...but some of their merchandise doesn't fit. The size stated is the size it should be...as said...try a reputable distributor; or even Ace Hardware. :)
 
A lot of new cotter pins are made in metric sizes which doesn't always work out so well. Ran into that when working at Deere dealer. To me , even worse than that is the flat washers. A lot of 1/4 inch washers will accept a 5/16 inch bolt and right on up the sizes. I know you need a little room over nominal size but not that much.
 
Mike just hit the nail on the head. Cotter pins are "supposed" to go in loose so that you can turn them as needed in order to bend the tabs. I've even had one cotter pin that I had to remove that didn't even have clearance to bend the 2nd tab - wasn't enough room to spin the pin more than about 20 degrees total. ...I replaced it with a nail. :mrgreen:
 
I think it depends on the industry and applications of the cotter pins that determine whether the size is actually true. In aviation the pins fit tighter than in agriculture applications and I have personally found that to be true. When I was adjusting linkages on a Super A I originally used cotter pins out of a box I bought at my local Case IH dealer and found them a bit sloppy even though they were the correct listed size. I brought home some made for aviation from work in the same size and they fit perfect.
 
For the throttle linkages on my old Deere's I just bought a box of them from the dealer to get ones that fit good.
 
I just for the sizes in them fit as will fit but when they do not go big enough you need to do something different with the box marked large size with 5/16" being the largest size. On the larger size 5'16" and up the stores do not carry them, the local welding shop-heavy hardware could not even get the 3/8" that I needed. And if they could I don't need a box of a hundred if they could get them and if they would actually fit the holes. 1/4" is also very hard to find. So where or how do you find when you need now and not in 2 weeks? To try to order from some distance place. And I use quite a few machinery washers or as some call them bushings and I can get them from Menards easier than I can from Fasenal that I would have to order them from. The job I am working on now I just needed 2 of the 5/16" ones so I put in the 1/4" listed as 5/16" x 2 1/2" and I will get buy but like to see them fit properly.
 
Any construction equipment dealers near you ? They use large cotter pins in many backhoes to hold the bucket pins.
 
They would have the size I need acording if they are full size. But like the 5/16" x 2 1/2" I was using yesterday and today I only needed 2 pins, not a pack of 50 and things was setting in the way too long to wait to get an order after I found that I needed them and thought I did have on hand what I did need.
 
That is the way things were designed. The only exemption was when the pin was used to keep a vent hole open from dirt in that they were supposed to move to do that.
 
(quoted from post at 22:33:30 07/26/17) They would have the size I need acording if they are full size. But like the 5/16" x 2 1/2" I was using yesterday and today I only needed 2 pins, not a pack of 50 and things was setting in the way too long to wait to get an order after I found that I needed them and thought I did have on hand what I did need.

I get most of mine from McMaster, As said above any good local supply house should have them in stock.

50 from them is cheaper than driving around trying to find what I need...... I often by the odd ones long and then you can shorten them for other things.

We have many equipment dealers and industrial supply houses here to pick from also.
 

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