Saw chain for a chain saw typically includes various links collectively designed to provide a cutting function. In various saw chains, these links may include such elements as tie straps, drive links, and cutter links. The cutter links are arranged in a sequence along with other components to form a complete chain.
Important to the function of a saw chain is a continuous and sharp cutting edge along the working surface or surfaces of the cutter links. This cutting edge dulls as it is exposed to the cut media during typical operation, and therefore needs to be refreshed/sharpened periodically. The cutting edge may be refreshed by removing a small amount of material through the use of a sharpening tool, such as a hand file or grinding wheel. After many instances of sharpening a cutter link over its useful lifespan, a substantial amount of material may have been removed. Once the amount of material removed exceeds certain limits, such as the manufacturer's specified limits, which are typically based on analysis of increased risk of material tear, use of the saw chain should be discontinued and a replacement chain used in its place. The current state of the art, such as described in U.S. Pat. No. 4,554,853, utilizes visual markings to delineate the extent of material removal that the saw chain manufacturer deems safe, however these visual markings can themselves wear out during normal chain saw operation rendering them useless as an indicator of the end of life of the cutter link(s) when they are needed to provide such a function.