Re: removing and adding chain links on motorized bicycle chain
"Procedure for Shimano® Chain
Some chains, including Shimano®, use chain rivets which are peened. This creates a "mushroom" effect at the ends of the rivets, which adds to the strength of the chain side plates. When a rivet is pressed even partially out, this peening is sheered off on the side pressed by the chain tool. If this rivet were reused, it would create a weak link at that rivet. In the image below, a Shimano® rivet is shown in an optical comparator, which magnifies the rivet. The original peening is seen at the bottom of the rivet. The top of rivet has the peening sheered off. This top section was pushed through the outer chain plate."
I thought maybe I crazy thinking chain pins were peened, but I did a double take on my bicycle and it has all shimano parts and theyre peened. I remember back in the 70s whenever I messed with a chain I needed to grind off the end of the pin to repair it. I dont ever remember having a chain tool back then, was too poor lol.