Originally Posted by cutebuns

It will be fine, I promise, I hate the plastic ones and they use them usually for the bobbin sensor, if you are not worried about the machine telling you when your bobbin is getting low they still sell the medal ones and I recommend them, I have mostly metal for all of my machines, two of them insist on it in fact,

Are you sure that it is the bobbin tension and not your top? thread the machine and stitch a straight line out on some scrap and tell me what you see, or if you can take a picture of both sides and post it and then we can tell what is up with it,