I would not recommend using only that kit and a drill press, by themselves, to finish an 80% lower. The way that kit works is to use the drill press to drill holes to a certain depth in the 80% block. Notice the jig piece that has all the holes in it. That is the top of the jig, once the jig is assembled. You use your drill press to drill down in all those holes in the jig. This removes most of the material in the block that needs to be removed, but not enough to complete the lower. Then you swap out the top of the jig will the other template to finish the job. However, this requires you to use a drill press as a mill. I would not recommend, as others in the comments have also said, using your drill press to try and mill out the remaining material. Your drill press was not designed for lateral forces. From this point, you need a router (wood router that is) that allows you to set the depth on it. You then need special milling bits that fit the router to clean out the rest of the material by making small passes at increasing depth. Do not buy regular machining mill ends, those will not fit in the router. Other vendors sell the milling bits you need for a router with their jig kits, or you can buy the bits separately. Obviously, the finish will not be as nice as a properly machined lower, but it will work.