Small holes that follow the line of hem stitching are a classic sign of needle damage. On jersey, a needle that is too large, blunt, burred or has the wrong point can cut the yarn instead of slipping between the loops. Once one loop is cut, the knit can open into a hole, sometimes straight away and sometimes after the garment is stretched or washed. If the holes appear only next to seams and not randomly across the fabric, start with the sewing process.

Look closely at the holes

Check whether the holes are on the needle line, how far apart they are and whether they appear on one machine's output or across lines. Holes at regular intervals along the stitch suggest needle penetration damage. If you can, trace the defective pieces to the operator or machine using bundle tickets.

Needles and settings

Ask which needle size and point the factory uses on hemming, and how often needles are changed. Ballpoint needles are commonly used for knits. A damaged needle can be replaced in minutes, but a routine is needed to catch it. Also review stitch density and thread tension; too many stitches per centimetre on a fine jersey increases the number of penetrations and the chance of damage.

Fabric finish matters too

Fabric that has not had enough softener or lubricant in finishing can be more prone to needle damage, even if its bursting strength measured with a method such as ASTM D3786 is fine. That is why a fabric test pass does not rule out a sewing problem. A quick sewing trial with different needles on the same fabric can show the difference.

Inspection and sorting

Holes are normally classed as a major defect. If your inspection is sampled under ISO 2859-1 and the lot fails, ask the factory to sort the whole lot and repair or replace affected pieces, then re-inspect. Stretch a sample of hems by hand under good light during inspection; early damage shows as broken loops.

Prevent it next time

Add needle size and type to the production sheet and require a needle control log. Check hems on washed pieces, after a named procedure such as ISO 6330, at the pre-production stage.