Whenever you’re removing a bolt that isn’t rusty, but it is hard to turn, it’s a good idea to check the threads on the bolt and the hole. If the threads got damaged in some way, when you try to put the bolt back in, it could cross thread or do even more damage. This has happened several times to me, which is why I have sets of both taps and thread chasers.
The most recent examples I can think of are a few seat mounting bolts that came out hard, and a starter mounting bolt that I needed to use my air wrench on because it was so hard to turn. I’m not sure what caused it in either case, whether it was someone installing the bolt improperly, or just something caught on the thread and damaged them. In both cases, I cleaned up the threads of the bolts and the holes, and when reassembling the components, the bolt screwed in with no problems. It may take a few extra minutes to clean the threads up, but it’s well worth it, especially if it avoids cross-threading or breaking a bolt.
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