That pic of "used" bolts were the ones off my airplane at overhaul, I bought new...but back then they were "only" about $25 each. I dug these out yesterday to "clean up" and there are so many nicks and gouges in shanks that these would be red tagged and scrapped, I would certainly never use them again....for aircraft, that is. Might make good fence post bolts.....
When I replaced my 150’s prop, I took one of the old prop bolts and used a hacksaw to cut some lengthwise slots across the threads. In effect, making it a cheap ‘thread-chaser’. I used it to clean any dirt and such out of the prop flange nuts before installing the new prop with new bolts.
