With A (Cotter) Key, Sissy!

For at least 4 years, I'd been waiting for an opportunity to finally use a cotter key (AKA cotter pin, but ever since I started listening to X Clan, I've had an obsession with anything that contains the word "key" in it). That, and I fervently enjoy making fun of people with body piercings by saying it looks like they were impaled with a cotter.
We had a situation with the gate where the nuts kept falling off. This was reminiscent of the time when I bought my welder and was wheeling it home aside my bike when one of the wheels fell off. Whoever built that cart were idiots. On one axle, there was a locknut, which fell off from the wheel rotating. On the other, a castle nut WITHOUT a cotter key! = not protected by the red the black and the green, sissy! They also broke the rule of never welding on galvanized steel! Probably a good thing they sold me their welder for $20. I ended up finding the nut after retracing my path for about a mile.

The solution: castle nuts with the anti-rotation cotter keys. These particular keys are 1/8" which means drill an 1/8" hole in the bolt where it goes through. The actual pin diameter is less than the nominal of course.

Firstly, putting on the castle nut and tightening it to the desired gate movability. Then marking the bolt where the hole is going to go.

I got a castle in Brooklyn, that's where I dwell!

Fortunately, I got a free milling machine 3 years ago, so I didn't have to go through the torture of trying to drill the holes by hand with a De-Walt pistol! This was especially helpful since the bolts we had were stainless which is considerably tougher to drill through than standard galvanized bolts. This is to say, we don't even live next to the ocean, but who doesn't like the unnecessary luxury of all stainless everything?

Drilling the 1/8" hole. Adding oil helped.

Incidentally, I found a special tool for removing cotter keys at a garage sale. Not that I'll need it for this installation, but I just felt like showing it.

After drilling the hole, deburring the threads with a triangular, or as it is curiously named, a 3 square file which doesn't make any sense since a square has right angles, not 60° ones.

Anti-rotation achieved. Even if you drill the hole in the wrong place by accident, there's always the slight chance that adding or subtracting a few washers can realign it. That, and the castle nuts index every 60° as you tighten or loosen them.

Now to make sure the key doesn't fall out, you twist the ends around.

Incidentally, I was recently able to perfect my brazing skills in a welding lab at school when I found what looked like a massive cotter key in the scrap bin and decided to braze it together. I noticed that it was one piece away from looking like an ankh AKA the "key of life", so I brazed the cross piece on as well. This will make a good addition to my ankh collection. I didn't feel any remorse in using that much brass. I heard somewhere that the steel industry is having problems with too much copper in their scrap. Here's your source: idiot college kids throwing brazing rods in the steel scrap bin!

Update:
As they say, there's more than one way to skin a cat. I found this brass castle nut and cotter pin exposed on a drinking fountain with the pin bent the other way. This begs the question, where the hell do you buy brass castle nuts? I was told if it wasn't on McMaster, it doesn't exist!