Why does my machine stitching pucker or come out uneven?

Two different faults get called the same thing. Puckering is the fabric being gathered up by the thread. Shifting is the two layers travelling at different speeds through the machine. They look similar on a finished seam and they have nothing in common, so the first job is to work out which you have.

What you'll need

• Scrap of the same fabric, doubled
• New needles
• Pins
• A walking foot (optional)

Step by step

1. Lay the finished seam flat and look at the ends.If the two pieces still line up at both ends but the seam is wavy and shorter than the fabric beside it, that is puckering. If one layer now overhangs the other at the finish, that is layer shift.
2. For puckering, fit a new, finer needle.A blunt or oversized needle pushes threads aside as it goes through and the fabric never recovers. On lightweight cotton or silk, a size 70 microtex makes a visible difference on its own.
3. Lengthen the stitch.Short stitches on light fabric put more thread into the same distance, and thread takes up space. Going from 2.0 to 2.5 or 3.0mm often removes puckering entirely.
4. Reduce the top tension a little.In small steps, testing after each. Tight top tension pulls the fabric up along the seam like a drawstring. Rethread completely before deciding the tension is wrong, because a thread out of the discs mimics a tension fault.
5. Support the weight of the work.Fabric hanging off the table drags backwards on the seam as you sew, and on a long seam that alone will pucker it. Keep the bulk on the table, at the same height as the machine bed.
6. For layer shift, pin across the seam.Every 8 to 10cm, at right angles to the stitching so the pins can be pulled as you reach them. Pinned layers are forced to travel together.
7. Sew with the fuller layer underneath.Since the feed dogs move the bottom layer further, put the piece you need to ease in there and let the machine do the easing for you.
8. Fit a walking foot for anything slippery or thick.It adds a second set of feed teeth above the fabric so both layers are driven. It is the proper answer for jersey, satin, PVC, fleece and multi-layer quilting.
9. Retest on a doubled scrap.Always the same fabric, same number of layers, same thread. A test on a different cloth tells you nothing about this seam.

Tips

• Tissue paper under a fine, slippery fabric stops it being pushed into the needle hole, and tears away cleanly afterwards.
• Pressing a seam properly hides a surprising amount of minor rippling.
• Two layers of a fabric behave differently from one. Always test doubled.

Common mistakes

• Reaching for the tension dial first — Tension is the fourth thing to check, not the first. Needle, stitch length and threading account for most puckering, and turning the dial before rethreading just adds a second fault to the first one.
• Letting the garment hang off the table while sewing a long seam — The weight pulls backwards on the stitching line and gathers the seam. Support the fabric level with the machine bed.

If it doesn't work

Questions people ask