Sewing needles needle point types

Table 11.4 Sewing needle cloth point types... 

Sewing needles come in a wide range of point types that are used for sewing many different types and properties of material. Indeed, you could write a book on the sewing needle alone. 

The most important aspect of needle design is the needle point because it has to penetrate the fabric without causing any damage to the material. It is also the most diverse part of the needle due to the many different types of points used. Needle points are designed for sewing on many different fabric types and seams. An example of needle point designs can be seen in Figure 6.21. 

Seam types used for woven fabrics include superimposed seams and double-lapped seams, especially when a high degree of strength is required, for example, in judo suits. Hemmed seams are also used on legs, and a lockstitch is used on areas that include labels and pockets. Sewing threads would be mainly staple core-spun polyester. Round-point needles are used for stitching these materials. 

When a tensile load is applied to a fabric seam, it has to overcome two types of frictional forces. One is the inter-yam frictional forces within a fabric, and the other is the frictional force of the stitch assembly. The former is dependent upon the crimp, yam diameter, fiber content, and number of cross-over points. The latter, however, is dependent upon the fabric properties like fiber content, type of yam (spun or filament), thickness, lateral compression, cover factor (threads per cm), bending, shear, tensile and surface roughness, and coefficient of friction. It is also dependent upon the properties of the sewing thread like fiber content, diameter, coefficiait of Mction, initial modulus, and extensibility. All of these properties, together with the machine variables like needle and bobbin thread tension and the stitch length, make up the frictional force of the stitch assembly. Thus different combinations of these would be expected to provide different frictional resistance and hence different loads at which seam slippage may take place. 

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