The Delta Model 40-640 is a popular, robust 20-inch variable-speed scroll saw known for its cast-iron table, dual parallel-link arm design (reducing vibration), tool-free blade changes, and electronic variable speed (400-1750 SPM), offering excellent accuracy for intricate woodworking projects saw known for its cast-iron table, dual parallel-link arm design (reducing vibration), tool-free blade changes, and electronic variable speed (400-1750 SPM), offering excellent accuracy for intricate woodworking projects