Industrial sewing machine troubleshooting: skipped stitches, thread breaks and loops

Skipped stitches, thread breaking, a bird nest under the plate: most problems on an industrial sewing machine have a simple cause, and the simple causes are worth checking in the right order before anyone touches the timing. This is the order we follow in our repair shop, problem by problem.

Check these five things first, every time

Most of the machines brought to us for “timing problems” are fixed by one of these. They take ten minutes together.

1. A new needle. The right system, the right size for the thread, put in all the way up, with the long groove and the scarf facing the way the manual shows. A needle that is very slightly bent or burred after hitting a rivet causes most skipped stitches.
2. Rethread the top with the presser foot up. With the foot down, the tension discs are closed and the thread does not seat between them. Make sure the thread passes through every guide and the take-up spring.
3. Check the bobbin. Wound evenly and not too full, sitting in the case the right way round, and the thread pulled under the tension spring. Clean lint out of the bobbin case and the hook area.
4. Check the thread. Industrial machines need left twist (Z twist) thread. Cheap or old thread, or right twist thread, untwists and breaks. Use the same thread on top and in the bobbin, or one size lighter in the bobbin.
5. Oil. A dry machine runs rough, heats up and drops stitches. Oil it the way the manual says, or check the reservoir on machines with automatic lubrication.

If you are not sure what needle goes with your thread, see our thread and needle size chart.

Skipped stitches

The hook point is not catching the loop of top thread behind the needle. In order of likelihood:

• Needle bent, dull, the wrong system or put in backwards.
• Needle too small for the thread, so the thread does not form a good loop.
• The material lifts with the needle (flagging): increase presser foot pressure or use a narrower foot.
• Thick seams, crossing a hem or welt: go up a needle size, slow down, raise the walking foot lift.
• If all of that is right, the hook timing or needle bar height has moved, often after the needle hit something hard. That is a mechanical adjustment.

Top thread breaking

• Threading missed a guide or the take-up spring.
• Top tension too tight for the thread. Loosen it and test on scrap.
• Needle eye too small, or a burr in the eye, the needle plate hole or on the hook point. Run your fingernail over them; a burr catches.
• Poor or old thread, or the wrong twist.
• Thread catching on the spool: use a thread stand with the guide straight above the cone.

Bobbin thread breaking

• Bobbin tension too tight. Hang the bobbin case by its thread: it should drop slowly when you jerk it lightly, and not slide on its own.
• Bobbin wound unevenly or overfull.
• Burr or damage on the bobbin case or the hook.

Loops or a bird nest under the work

Almost always the top thread, not the bobbin: it is not seated in the tension discs (rethread with the foot up), or the top tension is far too loose. Also check that the take-up spring is moving and not broken.

Loops on top

The reverse: bobbin tension too loose, or the bobbin thread is not under the tension spring in the case.

Uneven or short stitches, or the work does not feed

• Presser foot pressure too high on thick work, or too low on slippery work.
• Walking foot lift set too low for the seam you are crossing.
• Feed dog worn smooth, or set too low below the plate.
• Heavy material dragging off the table: support it, or add a puller on long seams.

Needle breaking

• Pulling or pushing the work while it sews. Let the feed do it.
• Needle too small for the material, so it deflects and hits the plate.
• Needle hitting the foot or plate because a foot is loose or the wrong one for the needle position.
• Sewing over rivets, buckles or heavy hems at speed.

When it is time to call

If the five basic checks and the list above do not fix it, the problem is mechanical: hook timing, needle bar height, feed timing, a worn or damaged hook, or a motor problem. These need gauges and experience, and a wrong adjustment can make a machine worse. That is where we come in.

We repair industrial machines of every brand in our shop in Ephrata, PA, or on site in Lancaster, Berks, Lebanon, York, Chester and Dauphin counties. Describe the symptom and we can often tell you on the phone whether it is something you can fix yourself. See repair and maintenance for what we fix and how it works.