Issue link: https://docs.hic.us/i/445658
10 Inspection before starting work Chapter 1 4. Inspection before starting work Before starting work, execute inspection (including cleaning, lubrication) of each part. Spot Check Covers Covers might have been attached incorrectly. Upper thread The thread might have been passed incorrectly to each part. The tension might have been inadequate. The thread might have entwined around frame/drive system. Under thread The under thread (bobbin case) might have been set to rotary hook incorrectly. The tension might have been inadequate. Needle The needle might have bent. The direction of needle might have been wrong. The needle might have been broken. Rotary hook Cleaning/lubrication might have been performed in inadequate frequency. Tension base switch The switch of head to use might have been turned ON. The switch of unused head might have been turned OFF. RR04