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Two threads that catch each other

How Does a Sewing Machine Stitch?

The needle never carries the thread all the way through — it makes a loop underneath, and a second thread hooks into it.

The eye is at the sharpendOnly a loop ever goesthrough the clothA second thread waitsunderneathThe two lock togetherinside the fabric
Nothing is ever pulled all the way through.

  1. Step 1 of 5

    Hand sewing drags the whole thread through.

    By hand The whole length passesthrough, every stitchBy machine Only a small loop evergoes through

    Every stitch by hand pulls a metre of thread through the cloth, then a bit less, then a bit less. A machine could never do that a thousand times a minute.

  2. Step 2 of 5

    The eye is at the point, not the top.

    A machine needle The eye sits right bythe tip

    That single change is what makes a machine possible. The thread arrives at the far side of the cloth the instant the needle does.

  3. Step 3 of 5

    Rising slightly makes a loop underneath.

    1 The needle goesdown2 It lifts alittle3 A loop bulgesbelow the cloth

    The needle goes down, then lifts a couple of millimetres. The thread does not follow immediately, so a small loop bulges out on the underside.

  4. Step 4 of 5

    A hook carries a second thread through that loop.

    1 A hook catchesthe loop2 It sweeps itround thebobbin3 The two threadsare linked

    Underneath sits a bobbin of its own thread. A hook catches the loop, sweeps it right around the bobbin, and lets it go with bobbin thread trapped inside.

  5. Step 5 of 5

    Pulling both tight hides the knot inside.

    Top thread pulled upby the take-uparmThe lock in the middlehidden insidethe fabricBobbin thread held downby its ownspring

    A take-up arm hauls the top thread back up while a spring holds the bobbin thread down. Balanced right, the lock ends up in the middle of the cloth.

    A domestic machine sews about 1,000 stitches a minute — roughly seventeen loops caught and locked every second.

The short version

A sewing machine stitches by pushing a loop of top thread through the cloth and hooking a second thread through it, then pulling the lock into the middle.

Try it yourself

Turn the handwheel of a machine slowly with the plate off. You can watch the hook swing round and catch the loop.

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