Originally Posted by
brit151
I did that with an 8mm hex, pulled the pedal off and I'm left with what you see in the bottom picture. Maybe I need to hit it harder to loosen it?
Wait what? You're holding the crank in your hand. The crank is the thing the pedal attaches to. You have no need to remove what's left in the bottom of the crank. But if you want to, you need a pin spanner to remove the outer ring that's around the 8mm.