Sewing Tools, Equipment and Machine Maintenance
Scope
Identification, correct use and maintenance of sewing machines, needles, feed systems and cutting equipment.
Core rules
- Needle parts: shank, blade, scarf, eye, point. Sizes 60/8 fine, 90/14 medium, 110/18 denim. Sharp point for woven, ball point for knits, cutting point for leather.
- Machine types: single-needle lockstitch, overlock, flatlock, buttonhole and bartack; each has its own needle system and gauge.
- Stitch balance: top and bobbin tension matched so the lock sits inside the fabric; 10-12 SPI for seams, lower for topstitch.
- Feed: feed dog height and differential feed set for the fabric; too high causes puckering.
- Maintenance: daily lint removal under the needle plate, oil to manual spec, check belt tension and timing, replace bent or dull needles, never drop the hook.
Worked example
A lockstitch machine skips stitches on cotton poplin. Reasoning: check cheap causes first - bent or blunt needle, wrong size, wrong thread path - then needle bar height and hook timing. A 90/14 needle on fine poplin is too heavy, so switch to 70/10 or 80/12 and rethread. Adjust timing only after needle, thread and tension are verified.
Traps
Turning the bobbin tension screw first; using a ball-point needle on woven fabric; over-oiling the hook; forcing a machine with a jammed bobbin; ignoring the manual's oil grade.