Originally Posted by HillRider

"Peened" rivets (aka pins) are flared at the ends to make a strong connection in thin chains like 9-speed and above. Pushing them out breaks off the flair and reams out the hole in the side plates leaving a weak connection at that point if that pin is reused. A proper connection requires a quick link or a specific joining pin like Shimano provides. I do like quick links but have had no problems with Shimano's specific joining pins when used once as specified.

Originally Posted by zacster

On older chains for 5/6/7 you could push the pin out fairly easily with the tool. With the new chains you have a hard time getting the pins out and it takes a good deal of force to get them out because they are flared as everyone here is saying. Shimano has one way of attaching chains, Campy has another, but I use KMC chains now with the master link which is so much easier.

Originally Posted by dedhed

​​​​​​https://www.orbitform.com/resources-...ed-peen-tools/