Machine Setting, Threading and Basic Maintenance
What the exam tests
Threading sequence, bobbin winding and seating, and routine cleaning and oiling. Expect questions on why a thread path is wrong and what maintenance a machine needs each shift.
Upper threading order
Spool pin, then first thread guide, then tension discs (presser foot up so the discs open), then take-up lever, then needle bar guide, then needle front to back. Always raise the presser foot while threading and lower it before sewing.
Bobbin and lower thread
Wind the bobbin evenly through the bobbin-winder tension, disengage the handwheel or winding lever, and stop when full. Insert the bobbin so it turns in the direction shown in the manual, thread through the case slot and under the tension spring. Hold the bobbin case still and turn the handwheel to bring the bobbin thread up.
Maintenance
Brush lint from under the throat plate, bobbin case and feed dogs after every shift. Oil only the points named in the manual, one or two drops, and never on the belt or motor. Change the needle after about 8-10 hours of sewing or at the first sign of a burr. Wipe the machine, cover it, and log the work.
Needle choice
Fine fabrics 9/11, medium cotton 14, denim or canvas 16; knits use a ballpoint needle.
Worked example
The thread forms a bird's nest under the fabric. Reasoning: either the upper thread missed the take-up lever, or the presser foot was down during threading so the discs stayed closed, or the bobbin is in the wrong way round. Fix the upper path first, re-seat the bobbin, then test on two layers of scrap.
Traps
Adjusting the bobbin screw before checking the top path; winding the bobbin with the machine fully threaded for sewing; over-oiling; leaving a loose needle clamp screw.