If your machine has jammed and fabric or thread is stuck, clear it carefully before doing anything else. Forcing the machine will make things worse.

• Stop sewing immediately to avoid making the tangle worse
• Raise the presser foot and needle to release the pressure on the fabric
• Gently snip the tangled threads with small scissors until the fabric is free - do not pull and do not use the automatic thread cutter if your machine has one.
• Remove the needle plate and clean the bobbin area of any loose threads or lint

The upper thread is the most common cause of thread bunching. Even if you think it is threaded correctly, a complete re-thread from scratch often solves the problem immediately.

• Remove the upper thread entirely and re-thread from scratch.
• Raise the presser foot before threading - this opens the tension discs so the thread seats properly.
• Make sure the thread passes through the take-up lever and all thread guides in order.
• Check the spool for snags, knots or tangles.
• Use the correct spool cap size to stop the thread catching as it unwinds.

Although the upper thread is usually the culprit, it is worth checking the bobbin too while you are in there.

• Rewind the bobbin evenly - an uneven wind can cause tension issues
• Reinsert it in the correct direction for your machine - check your manual if unsure
• Make sure the thread is pulled through the bobbin tension slot properly
• Clean the bobbin case of any lint or stray threads

If re-threading has not fixed it, tension is the next thing to look at. Bunching underneath the fabric usually means the upper tension is too loose.

• Try tightening the upper thread tension slightly and test on a scrap of fabric
• If the upper tension is too loose, the bobbin thread pulls up too much — causing loops underneath
• Only adjust bobbin tension if necessary — upper tension adjustment usually does the job

A damaged or wrong needle can make tension problems worse. It is worth ruling this out if the steps above have not fixed things.

• Replace any bent, dull or damaged needle with a fresh one
• Make sure you are using the right needle type — Ballpoint for knits, Sharp for woven fabrics
• Match thread weight between the upper and bobbin threads — mismatched weights cause uneven stitches
• Use good quality thread — brands like Gütermann help prevent breakage and tension issues

Bunching at the very beginning of a seam is often caused by thread tails getting pulled under the fabric. A simple habit change prevents this entirely.

• Hold both the upper and bobbin thread tails behind the presser foot for the first few stitches
• This stops the threads being dragged down into the feed dogs before they have formed a proper stitch

A build-up of lint in the wrong places can affect tension and stitch formation. A quick clean often makes a noticeable difference.

• Remove lint and dust from around the bobbin case, feed dogs and tension discs
• Oil the machine if your model requires it — check your manual for where and how much
• Make sure the feed dogs are raised and moving properly

Before returning to your project, test your stitches on a scrap of the same type of fabric. This confirms the fix is working and gives you a chance to fine-tune tension before you sew on anything important.