There's a reason that the better chain tools have the ability to replace their drive pins and the OP just found out why. One technique I use is when the tool is positioned on the chain and the initial twist of the handle (or the first bit of the tool's pin driving on the chain's pin) I will back off the tool pin a half turn or so then re tighten it. I have felt the two pins become better aligned this why. And it's usually the pins not lining up properly that caused the tool pin to bend/break. Andy.