Reference
Troubleshooting
Symptoms, common causes, and what to try first. Most sewing-machine problems trace back to threading, needle, or tension — usually in that order.
The universal first move: re-thread
Before you do anything else, re-thread the machine completely — both top and bobbin. Lift the presser foot, remove all thread, follow the threading guide from scratch. Most of the symptoms below have re-threading as the answer in 60% of cases. It takes thirty seconds and saves you ten minutes of chasing the wrong fix.
Skipped stitches
Symptom: The stitch line has gaps — every few stitches, no stitch was made.
| Likely cause | Fix |
|---|---|
| Dull or bent needle | Replace with a fresh needle in the right size |
| Wrong needle type for the fabric | Knits need ballpoint; denim needs a jeans needle |
| Top thread not in the take-up lever | Re-thread top |
| Fabric being pulled instead of fed | Let the feed dogs move it; your hands only guide |
| Bobbin loaded backwards | Remove bobbin, reseat correctly |
Puckering (fabric scrunches along the seam)
| Likely cause | Fix |
|---|---|
| Tension too tight (top) | Loosen top tension by half a number, test on scrap |
| Stitch length too short | Lengthen to 2.5 or 3.0 mm |
| Needle too large for fabric | Step down a size |
| Thread too thick for fabric | Switch to all-purpose 50 wt |
Thread keeps breaking (top thread)
| Likely cause | Fix |
|---|---|
| Tension too tight | Loosen top tension |
| Burr on the needle eye or a thread guide | Replace needle; inspect guides for nicks |
| Thread caught on something on its way down | Re-thread, making sure no thread is wrapped around the spool pin |
| Old or low-quality thread | Use fresh polyester all-purpose for tests |
Thread keeps breaking (bobbin thread)
| Likely cause | Fix |
|---|---|
| Bobbin wound unevenly or too full | Re-wind the bobbin, don't fill past the rim |
| Lint in the bobbin case | Open the case, brush out the lint with a small brush |
| Bobbin sitting wrong in the case | Remove and reseat |
Bird's nest (mass of tangled thread on the underside)
This looks dramatic but the cause is almost always one thing: the presser foot was down when threading, so the top thread never seated in the tension discs. With no top tension, the thread piles up under the fabric in a tangled mess.
Fix: lift the presser foot, remove all thread top and bobbin, re-thread with the foot up. Sew a test on scrap. Bird's nest gone.
Needle hits the bobbin case ("clunk" with each stitch)
Stop sewing immediately. This means the needle is being deflected — it can break, bend, or damage the bobbin case if it continues.
| Likely cause | Fix |
|---|---|
| Needle inserted slightly off-center | Loosen the needle clamp, push the needle all the way up, retighten |
| Bent needle | Replace the needle |
| Bobbin sitting too high | Reseat the bobbin |
Stitches loose on the underside (loops of top thread visible underneath)
Top tension is too loose. Tighten by half a number, test on scrap. Repeat until both sides of the stitch look clean.
Stitches loose on top (loops or "thread dots" of bobbin color on top)
Top tension is too tight. Loosen by half a number, test on scrap.
The machine makes a knocking or grinding sound
Power off. Open the bobbin compartment and check for lint — a thick build-up of lint can interfere with the bobbin race. Brush out (don't blow — your breath has moisture). If sound persists, the machine needs an oiling or a service. Don't keep sewing through it.
Stitches look fine on top but fabric bunches into a "tunnel"
Usually a sign you're sewing two layers and one is feeding faster than the other. Add more pins along the seam, or use a walking foot if you have one. Stretchy fabrics are most prone to this.