Installing Cotter Pins

josephteasdale

Hi guys,

I've read a fair bit about installing cotter pins but have one question before I can be happy with the pins and get back on my bike!

I've bought new pins, they seem to fit; a couple of hard taps with a hammer and half a cm of thread protrudes from the other side of the crank arm, allowing me to do the nut up to hold it all steady. Does this mean I am free from the hassle of filing or from anybody's experience will filing be essential on new pins?

Hope I've given enough info.

Cheers.

arthur_scrimshaw

I don't have recent experience of fitting cotter pins but why would you need to file the pins? Is this some way of preventing the nut from undoing? If so maybe use loctite or similar?

Sawilson

Not fitted pins for years but remember filing them on the flat to get them to project through far enough to get the nut on.
Don't know if there were different size pins or if there were different sized cranks or BBs, but it was the only way to get them to fit properly.
The best fun was knocking the hell out out of them to remove them, if that didn't work out came the blowtorch and if that failed out came the drill.
Square taper was like heaven.

arthur_scrimshaw

Sawilson wrote:

Not fitted pins for years but remember filing them on the flat to get them to project through far enough to get the nut on.
Don't know if there were different size pins or if there were different sized cranks or BBs, but it was the only way to get them to fit properly.
The best fun was knocking the hell out out of them to remove them, if that didn't work out came the blowtorch and if that failed out came the drill.
Square taper was like heaven.

Ahh that makes sense, they come with flats on them don't they but as you say, you can adjust the fit by filing.

Sawilson

Sorry didn't quite answer OP question, filing was only required if you couldn't get the pin in far enough sounds like you have fitted them correctly.

team47b

I have recently changed two cotter pins, if they go through the holes then you have installed them with the spindle in the right place as they won't go through otherwise, if you have enough thread to fit the nut then the taper is aligned correctly, the purpose of the nut is to retain the pin so it doesn't fall out, it is not the tightness of the nut that stops the crank from slipping it is the taper on the pin, so filing will only increase the likelihood of the crank moving. Cotter pins are not precise bits of engineering as it is the taper that makes up for any difference in size.

Please bear in mind that my wealth of understanding on the subject of cotter pins is based on the ones I have just fitted to the front suspension king pins of my 1956 BMW Isetta bubble car

josephteasdale

Cheers guys, you've confirmed what I wanted to know in super quick time. Brilliant stuff.

Now I can get the old girl back out on the road ASAP!

BillyMansell

If there's enough thread exposed to pass through the nut then you shouldn't need to file the flat, otherwise file a little and test for fit frequently. If you file too much you can run out of thread and even if you fully tighten the nut the crank will move on the axle.

team47b

...but more importantly what bike is it?