I am trying to remove the upper tension unit on my featherweight. Just purchased and the previous owner put it on wrong so I cannot thread it properly. According to instructions on line, I am supposed to be able to pop it off after turning to the number one. No luck. so the question is how forceful can I be. Can I use a screw driver and pop it off? Don't want to ruin anything. I would appreciate any suggestions. Thanks in advance for any help.