Hook Cerliani - Common Sewing Problems User Manual

Common sewing problems, their

PROBLEMS CAUSES

- incorrect balance between upper and lower tension - uneven pu ll­off of the upper thread - worn upper tension unit - broken or
weakened check spring - bobbin unevenly wound - worn

Uneven stitches

Upper thread

breaking

Lower thread

breaking

bobbincase tension spring - too coarse or unvene thread - incorrect
needle for the thread

- incorrect timing of hook and needle - too little clearance between
base and retaining finger - incorrect timing of base and looper ­base does not move freely in hook - poor hook lubrication

- incorrect threading of upper thread - upper thread tension too
tight - damaged thread guide - bent or blunt needle - incorrect
needle for the thread - needle hole of needleplate too small - poor
quality thread, too dry or badly stored - needle overheating ­defective bobbincase latch

- incorrect timing of hook and needle - too little clearance between
base and retaining finger - incorrect timing of base and looper ­damaged hook point - scratched needle guard on the hook - sharp
edges on feed dog or needle hole

- lower thread tension too tight - bobbincase threaded incorrectly ­bobbin unevenly wound - damaged or poor quality bobbin ­damaged bobbincase

- sharp edges or needleplate needle hole - feed dog too sharp
behind the needle

causes and repairs

PERSON

INVOLVED

Operator

Technician

Operator

Technician

Operator

Technician

Skipped stitches

Needle unthreading

at start

Looping underneath

material

Needle breaking

- needle not inserted correctly - damaged or blunt needle - needle
too thin compared to fabric - incorrect needle point for fabric - t oo
elastic or badly wound thread - upper thread incorrectly threaded

- needle bar height wrong - incorrect clearance between needle and
hook point - needle and hook not correctly timed - damaged hook
point - needle hole in needleplate too large - needle hole in feed
dog too large

- too little upper thread coming through the needle - too little
bobbin thread coming out of the bobbincase

- thread trimmer leaving bobbin thread to short - tension
tightening during trimming operation

- lower thread tension too tight - upper thread tension too lose ­bobbin not running smoothly - upper thread too stiff or too variable

- needle eye too small for thread - pressure or presser foot too
heavy

- hook is not passing the thread easily - incorrect timing of needle
and hook - incorrect timing of base and looper - feed dog timing
too advanced - needleplate or presser foot do not have the correct
thread groove

- incorrect needle for the material - material too thick for the
sewing machine - sewing over buttons, pins, zips etc. - bobbincase
incorrectly inserted - using up the lower thread on machin es with
roller presser foot - needle stop not correctly timed

- feed dog timing retarded - needle striking hook point - needle
guard fitted too far back - needle and hook not correctly timed

Operator

Technician

Operator

Technician

Operator

Technician

Operator

Technician

- starting sewing with too long or uncontrolled upper thread ­upper thread tension too loose - sewing at the start or end without

Hook jams

material
too little clearance between base and retaining finger - base not

running smoothly in hook - insufficient lubrication

Operator

Technician