This post is about threads.
When I first got the bike, I was going to fit a bottle cage to it, a) because I had a spare one after picking up an end of line carbon one for $29.95 and b) to stop creatures entering the downtube and eating the bottom bracket bearings. The top screw went in fine, a little firm in places. The bottom one however would not go past half way, forcing it further (gently) started to flatten the threads.
Enter my tap and die kit. After measuring the thread with the thread gauge that came with the kit, I selected the right size tap. I used the tap to clean out the threads. Then it was easy to get the bottom screw in and attach the bottle cage.