Photo of a flat honing machine. Its purpose is to machine parts to a precise thickness and improve their flatness.
In the photo, each of the five sprocketed carriers are loaded with five disk shaped parts. The parts and carriers are sitting atop a greyish-green surface that is the lower abrasive surface. The upper abrasive surface is not pictured, but it is the same as the lower. In operation, the both surfaces are pressed together while the parts and carriers are sandwiched in between. The gap between is carefully controlled since it determines the thickness of the machined parts. The abrasive surfaces rotate in opposite directions to create a shear machining force. At the same time, the inner ring of pins also rotates and causes the carriers to rotate like a spirograph. The combination of these motions greatly improves the dimensional quality of the finished parts.