randyjawa 

Like the old fool that, it would seem, I am, I apparently forgot to proper press and tighten up the cotter pins on the crank of my recently restored Torpado. Out for a ride, the other day, I noticed a wee hitch with each crank rotation. Being several kilometers from the cottage, I had to ride the old girl home very carefully. I pressed the cotters into place and then secured them with the cotter nuts. However, I am not confident that they will hold indefinitely. With that in mind, I hope to order a set, or two, through Ebay or even from another forum member (through the for sale forum).

I want good quality 9mm pins and am hoping that someone can recommend something worth buying. Thanks and looking forward to getting this sorted out...

oneclick 

https://www.bikesmithdesign.com/Cott...s/cotters.html

randyjawa 

Thanks very much for the heads up on that seller. Not only does he offer good quality cotter pins but a wealth of information is available there also.

RustyJames 

I’m ignorant but how far “up” should the cotter head protrude? I’ve seen some that are almost flush but others that are very tall above the crank arm. If I had to guess, some would say that if they’re tight and the arms are 180° all is good.

oneclick 

That doesn't really matter, except that if it does not protrude you may have other issues, to wit:

If the nut can not screw down on the threads enough to keep the pin in place (because the shank is sticking out that end) then either the pin is the wrong diameter or the cut is too deep.

You do want the pins to go deep enough to have a portion of their flat bearing on the whole of the flat on the axle.

And just to make it fit with the rest of the cycle world, they're not all the same length.

Moe Zhoost

You basically want the nut to engage the maximum amount of threads without any protruding past the nut. Most cotters will need some filing to fit right. One needs to be careful when filing to keep the surface flat. If you rock the file, even slightly, you'll crown the taper.