TABLE OF CONTENTS Conventional rotary barrel tumbling is the original mass finishing technique. Ancient Chinese and Egyptians used tumbling barrels with natural stones as media to achieve smooth finishes on weapons and jewelry. The process was known as barreling, rattling, or tubbing. Stories were reported in 1948 that chain type armor in the medieval years of jousting required tumbling, as indicated by the statement: "Ye apprentice was required to place the parts in a cask along with small jagged stone fragments and tend to roll the cask about upon the ground until all the parts were smooth" (Beaver 1948a). Edmunds in England was the modern developer of the process in 1885 (Beaver 1948a). Barrel finishing is now a vastly improved process compared to the old-time tumbling operations, but it is generally slow. As a result, the more sophisticated mass finishing processes discussed in later chapters are making the barrel obsolete for most applications. However, barrel finishing is a versatile means of edge and surface conditioning, equipment costs are generally low, operation is simple, and there are still applications where this is the most economical process.
Barrel finishing is a low-pressure abrading process generally performed by the controlled sliding and rolling action of workpieces, media, compound, and water. Not all these ingredients are used in all applications. In a rotary or tumbling barrel (Fig. 8-1), the upper layer of the workload has a sliding movement. As the barrel rotates, the load moves upward in the barrel to a turnover...
