Carr and Latham’s Technology of Clothing Manufacture 100
Figure 3.54 Special needle shapes. (i) Blind stitch needle. (ii) Pick stitch needle.
pucker, fabric damage and needle heating effects. Needle strength must remain adequate despite smaller size. Needle thread loop formation is critical if slip stitching is to be avoided, especially on zig-zag machines where the hook cannot be set as close as on straight-stitch machines. Needles are available in a wide range of sizes and the choice of size is determined by the fabric and thread combination which is to be sewn. As has already been suggested, correct size is essential to good sewing performance but as fabrics tend to become finer and, in many cases, more densely constructed, the demand is for needles and threads that can be used satisfactorily in smaller sizes. If the needle is too small for the thread, the thread will neither pass freely through the eye nor fit properly into the long groove and will suffer from excessive abrasion as a result. This can lead to costly thread breakages in production because the machinist must stop to rethread the needle and possibly also to unpick some of the stitching so that a join does not show in an important part of the garment. Even worse, a break in a situation of multi-needle sewing with fabric running through folders could be impossible to repair. The use of too fine a needle when sewing heavy plies of material can lead to the needle being deflected, which can affect the stitch loop pick up and cause slip stitches; it can even lead to needle breakage. If the needle is too large for the thread, there will be poor control of the loop formation which may cause slipped stitches. There will also be holes in the fabric that are too big for the stitches and give an unattractive seam appearance. An unnecessarily large needle also tends to give rise to damaged fabric along the stitch line and, in closely woven fabrics, pucker along the seam line due to fabric distortion. Different needle manufacturers use their own nomenclature to describe needle sizes but the simplest sizing system is the metric one. The metric size or Nm of a needle is related to the diameter at a point