Hi Gabriel. As Larry said, the saw set is to bend the teeth outward (alternating to the left and right) to make the kerf in the wood wider than the saw plate so the plate does not bind in the cut. You asked whether you only set the teeth on old saws that are being restored and when you change your saw from cross cut to rip cut. No, you also do it on new saws after several sharpenings. Your Veritas dovetail saw comes sharp and with the teeth set. But you will have to sharpen the saw at some point. That might be after weeks, months or years, depending on how much you use it — I do it every few months on saws I use a bunch. You do not want a dull saw. If the teeth on your saw need a lot of work, e.g., you are restoring an old saw or your screwed up trying to sharpen you new saw, you will probably have to joint the saw (leveling all the teeth with a file) as well as sharpening. Then you will have to reset the teeth. But if you are just doing more modest work on your saw, say a touch up to restore the teeth to full sharpness, you probably do not have to joint or set the teeth every time. In fact, you might only set the teeth after two or three sharpenings. As Larry says, if the saw begins to bind, you know you needed to set the teeth. But I do not usually wait till my saw binds. I set the teeth very three sharpenings. (Oops! Full disclosure. I have one saw that I forgot to set for about five sharpenings and yes, it binds. Guess I have to set the teeth now.)