What is the difference between hardplating and screening witht the buffer??

Both processes utilize the slow speed buffer (which is called a buffer but really is a wood sander @175 rpm). The difference is when hardplating, one uses a driving block that is ridgid with a bolt and nut to bolt sandpaper on to it. Some blocks will have a dense 1/4" foam on them. It is in essence circular sanding similar to a large edger. Screening employs using a driving block that has short stiff nylon bristles to grip a driving pad. There are different pads one can use. 3M has a 1/4" white pad just for driving screens while some finishers prefer a thicker 1" pad. The pad drives a sanding screen, which is different than sandpaper. The driving pad is soft and allows the screen to be more flexable. Hardplating is used when sanding materials of varying hardnesses or mixed medias and parquets. It is supposed to help eliminate dishing that can happen on open grained hardwoods (like oak) and essentially flatten the floor better after drum sanding. Screening will NOT do this as it is too flexible.