Imagine you are standing on the platform of a merry-go-round, and it is rotating at the rate of one revolution per minute (1 RPM). If you are standing at the center point of the platform, the speed in which you are rotating is pretty darned slow. Should you decide to venture towards the edge of the platform, your speed of circular motion would increase as you approach the edge (not the speed in which you are walking, but the speed in which you are traveling in a circular direction).
The increase in speed is due to the fact that although the merry-go-round’s rate of travel is still 1 RPM, you are traveling a longer circular distance the farther you venture from the center of the platform. If we rate your speed using a common measurement such as miles per hour (MPH), then for any given RPM, your speed will increase as the diameter of the path you are traveling gets bigger.
The same dynamic occurs when you use a large diameter pad as opposed to a small one. Therefore, for any given RPM setting, a large pad will reach a higher MPH rate along its edge versus a small one. The speed along the edge of the pad is referred to as tangential speed (not common), edge speed (common), and linear speed (also common).
The increase in speed can change the dynamics of a pad entirely. Higher edge speeds can cause the pad to heat the polishing surface more rapidly, or raise the temperature to a higher level altogether. In addition, a potential exists that sees the pad becoming less pliable as it travels more rapidly. This is because there is less time for the pad to contour to the small nuances of a paint surface. Instead of contouring, the pad compresses, and then ends up forcing its way through nuances, or obstacles.
If the area you are working on allows you to physically fit a large pad in the vicinity, start with a large pad first. By tilting the pad and then adjusting speed and pressure, you can mimic the total surface area of a small pad. You’ll get more edge speed if you need it, yet you’ll be working with more surface area, so the pad can be used longer before it needs cleaning. Obviously, this information applies to all sorts of buffing pads, including foam, wool, microfiber, and microfinger pads.