Stop sewing immediately. A knocking or clunking noise usually means the needle is striking metal, and every additional stitch risks damaging the hook or the timing — which turns a two-minute fix into a workshop repair.
Check, in this order.
The needle. Bent, blunt, wrong way round, or not pushed fully up into the clamp. Any of these puts it out of position and it strikes the plate or the hook. Change it.
The stitch width against the needle plate. A zigzag set wider than the needle hole allows, or a twin needle in a machine set to a wide zigzag, hits the plate on the first stitch. Set the width manually before using a twin needle.
The presser foot. Wrong foot for the stitch — a straight-stitch foot with a zigzag selected has a narrow slot and the needle hits it.
Lint or a thread nest in the bobbin race. A jam there makes the hook labour, which sounds like a knock.
Something in the machine. A broken needle tip, a pin, or a fragment in the race. Remove the plate and look.
If it persists with a new needle correctly fitted, the correct foot and a clean race, that is a timing question and it belongs with a technician. Continuing to sew through a knock is how a machine ends up needing a re-time.
Questions people actually ask
It knocks only on thick fabric.
Usually needle deflection: the needle is too fine and is bending into the plate. Fit a heavier needle and slow down.
Can I keep sewing if it still stitches?
No. It may still stitch for a while, and each strike moves the hook a fraction closer to a re-time. Stopping costs you five minutes; not stopping can cost a service.
Last reviewed 2026-08-11