When a tool chatters it gets dull faster because it must keep cutting through the previously machined surface that has been "work hardened" by machining. As you can imagine, there are limits to how much you can increase feed rate, so the answer lies in adjusting both speed and feed to achieve the proper cut.
Proper cutting speed is the rate a particular material can be machined without damaging the cutting edge of the tool that is machining it. It is based on the surface speed of the material in relation to the cutter. This speed is a function of both the RPM of the spindle as well as the diameter of the part or size of the cutter, because, as the part diameter or cutter size increases, the surface moves a greater distance in a single rotation. If you exceed this ideal speed, you can damage the cutting tool. In the lathe and mill instructions, we give some examples of suggested cutting speeds, but what I wanted to get across here is that it isn't a slow process. A tool can be destroyed in just a few seconds. It isn't a case of getting only one hour of use instead of two. The cutting edge actually melts. If you machine tough materials like stainless steel, you will ruin more tools than you care to buy if you don't pay a lot of attention to cutting speeds. Charts showing suggested cutting speeds for various materials are included in both the lathe and mill sections that follow.