Re: Locking/pinning as pain submission...
Oh, and Michael,
You've hit my exact point - when someone concentrates on causing pain, they invariably screw the lock up, when they concentrate on taking the centre they are way more likely to get the lock right, and when it's right it usually hurts like a bastard.
Try to cause pain, you'll get the angles and torsion on the joint wrong and cause way less pain than if you concentrate on locking the centre. Focus (Intent) is key.
The crazy good Aikidoka out there who can control uke without inflicting pain can do so because they have such good sensitivity and control they can apply just enough force to control, the rest of us tend to use either way too much (pain, but it works) or way too little (no pain and it doesn't work).