This standard specifies the basic parameters, types and dimensions, technical requirements, lubrication, test methods and inspection rules of single-stage shaft-mounted arc cylindrical worm reducers. This standard reducer (including three series: SCWU, SCWS, SCWO) is directly installed on the main shaft of the working machine. It is mainly used for reduction transmission of metallurgy, mining, lifting, transportation, chemical industry, construction and other mechanical equipment. The speed of the reducer worm shaft No more than 1500 r/min. The working environment temperature of the reducer is -40~40℃. When the working environment temperature is lower than 0℃, the lubricating oil must be heated to above 0℃ before starting. The worm shaft of the reducer can run in both forward and reverse directions.