This extract is from Sewing for Fashion Designers by Annette Fischer, published by Laurence King. This book is a brilliant reference guide not just for fashion designers but also for home stitchers covering sewing tools, materials, construction techniques, hems and seams.
What to Watch out for when Stitching Seams
When sewing fabrics together problems can occur when the thread tension is not correct, the needle or bobbin is not inserted properly, or the machine is not threaded correctly. Threading instructions for sewing machines and overlockers are included in the machine’s manual and should be consulted before you start sewing.
Always stitch a sample first:
• Use a sample piece of the material you are about to sew.
• Check you have chosen the right needle size and thread to suit the fabric type and weight.
• Always place two layers of fabric together when producing a sewing sample to check thread tension, needle type and stitch length.
Correct thread tension
A correct thread tension looks smooth and flat on both sides of the seam. The needle and bobbin threads interlock midway between the surfaces of the material.
Needle thread tension is too loose
The needle thread needs to be tightened if the stitching thread shows loops on the underside. On the other hand if the needle thread is too tight, it will pull up the bobbin thread and also show it on the topside. If this is the case, then loosen the needle thread tension, but avoid adjusting both needle and bobbin tension.
Bobbin thread tension is too tight
When loops form on the topside of the seam the bobbin thread needs loosening.
If seams on lighter weight fabrics are prone to puckering, loosen the thread tension a little and adjust to a larger stitch length.
This can happen when sewing fabrics cut on the bias or with some stretch. Make sure you only lead the fabric through the sewing process and gently push the fabric towards the foot; avoid excessive pulling and pushing. It might also occur if the pressure on the foot is too tight, in which case loosen the foot pressure.
Many factors can lead to skipped stitches. Check if the needle has been inserted in the right direction, is the right size and type, that the point is not dull or bent and the machine is threaded correctly.
If the machine is not threaded correctly, or the thread has not been placed properly inside the tension disks, a series of loops can appear. A stitch regulator on an industrial flatbed sewing machine. On this machine the stitch length can vary from 0–4mm.
This indicates that the tension is too loose on both the bobbin and needle thread, the machine has not been threaded correctly, or the thread has not been placed properly between the tension mechanism.
Images © James Stevens and Gary Kaye