a well set up band saw will cut dead straight,...there are cabinet shops that don't even have a table saw because the have a good size band saw,....it will do just about any ripping and crosscutting a table saw will do with equal precision and less waste. you are either, feeding too fast for the tooth count or your guide blocks/ wheels are not set close enough to the blade, or one side of your blade may have lost some set in places, from the teeth hitting a guide block or wheel. it only takes just a touch of the tip of the teeth to completely wipe out the tracking ability of a blade. you might also try a bit more tension on the blade. depending on the age of the saw, you might also check the top wheel's bearing and tracking plate's pivots. play in either of these will produce a wavy cut, as the blade will try to steer the wheel instead of the wheel steering the blade. you should not be able to rock the blade side to side from front to rear of the saw. as you face the diameter of the upper wheel grab the left and right side and see if you can rock the wheel back and forth. if there is anything more than barely percievable play, that is your wavy cut. that rocking steers the blade left and right as it cuts.