Is this crank usable or should it be replaced? I've been suffering from weird noises while pedalling for a couple of weeks.  Noise has been isolated to the left foot, its definitely not the right side.

After an inspection revealed no cracks or other badness,  I pulled the left crank off with a puller.

  The lip around the presser on the right hand side of the image?  That's compressed outward, and once I got the crank off the pusher of the puller was wedged in the taper.





The other two sides are only lightly marked.  The two sides pictured are the worst damage.

The crank was cleaned and refitted with a light coating of copper slip on the facing surfaces and it seems to be functioning fine.  But

Question: Is this crank safe?  Or is it vulnerable to further damage?
It's hard to tell if it will be OK, and it will depend on how heavy you are and how much pedaling torque you can produce.

The main problem you are going to face is not the reduction in area of the taper surface, but that the puller will have pushed the edges of the gouged area up, so that the crank will not fit quite properly on the spindle taper. Because of this you may find that you have problems with the crank staying on the spindle.

If you feel inside the taper with a finger tip (my pinkie fits inside a crank taper, and I have fairly big hands) you will feel an raised edge or 'burr' of material around the gouged area. You will want to very carefully file that off with a fine, flat needle file. It will only take a few light strokes to remove it.

When you re-install the crank, torque the retaining bolt up to the maximum allowed. Do a test ride and check that the crank is staying in place. Check the crank regularly when you ride after that. Hopefully it will stay in place.