Originally Posted by
neurocop
If the holes you refer to are the ones that attach to the BB spindle, you can take the spindle out (or leave it in the BB) and paint the square ends of the spindle with Dye-Chem and push the cranks onto the spindle ends, then remove the cranks and inspect the Dye-Chem for uneven rub-off. This will show even minute mating surface irregularities. Generally, however, spindle holes worn enough to cause problems will be apparent just by looking at and feeling the cranks when pressed onto the axle.
Good point. Often the damage can be seen. If the 'flats' inside the crank are not perfectly flat - if there is a characteristic dent on each of the flats caused by the corners of the spindle when it is slightly misaligned - then the crank is damaged and will likely never stay on the spindle even if they are properly torqued on. The Dye Chem is a great idea, too.