The Singer 457 has a plastic gear on top and a timing belt in the bottom. Spin the hand wheel (without a needle in) and check to see if the hook is spinning around the bobbin. You can remove the bottom to check to timing belt, and the top to see if the plastic gear has failed. A google search of "Singer 457" will turn up 'Becca's crazy project' where she describes replacing the gear on this machine. (most likely the problem)