Broken Tooth: Broken Tooth (断牙)
A tooth that has cracked or snapped, usually at the ends where the slider enters and leaves the chain or where a needle has struck it. Causes include excessive force, brittle material, moulding defects, burrs and sewing through the tooth row. A broken tooth causes jamming, gaps and possible injury from sharp edges. Inspection combines visual checking and careful handling, and prevention focuses on material toughness and sewing control.