Hi everyone, second hand bike recently handed to me. While giving it a safety check I noticed the left crank was missing it’s bolt. The crank is still securely embedded on the axle but I’d still like to add the bolt for safety. Problem I have is the thread of the axle was damaged by the previous owner, but only the start of it (first 0.5mms or so). There’s no “opening” for the thread on the bolt to go, I tried screwing a bolt as is but it wouldn’t go in anyway. I didn’t use much force as I didn’t want to ruin it further.
Questions I have are :
Is it doable and worth it to try and rethread the axle ?
The bb is otherwise running perfectly.
If so how would I proceed to make sure I don’t offset the thread compared to the existing one (which is in a perfect state).
Thanks in advance !
by SelzAegis
4 Comments
Don’t bother, buy another BB instead, they cost peanuts.
The measurements you need will be hopefully on the existing one, if not you need to measure the bottom bracket shell width and then the axle length. (68mm x118mm example)
Someone said don’t bother, but also, why not? Don’t go buy some tools to do it, but if you have a tap, just go ahead and thread it in. You can even oversize just that one side if you can find an appropriate bolt that fits the BB and crank. It takes a few minutes and you might be good to go. First try the appropriate tap and see if you have a longer bolt as well. If that doesn’t work, oversize it, even going from Imperial to Metric or vise versa if you have the right bolt on hand.
We have to keep up our skills at actually fixing things, or nobody will be able to in the future. It’s not hard.
By tapping you are by definition making the threads slightly larger, thus reducing the metal and integrity of the square taper BB. It’s not a good idea but you could do it.
Yes, perfectly do-able. It maybe that the thread just want “chasing “,but as said, don’t buy any tools for it.