The sewing machine needle, despite its low cost, is one of the most important components used when sewing. It performs the vital function of transporting the sewing thread to the sewing machine mechanism to form the stitches and protects the sewing thread during its passage through the fabric with minimum distortion to the fabric. Industrial sewing machines are capable of exceeding speeds of 6000 stitches per minute. When stitching closely woven fabric at this speed, the action of the needle generates friction and the needle can reach temperatures of 400 degrees centigrade. Not only does the temperature damage the fabric, but the hardness of the needle can be affected. Natural fabrics such as cotton can withstand high temperatures without much damage but a resin finish coating on a fabric or synthetic fabric,such as nylon, will melt.
Parts Of The Needle
Needles are available in a range of sizes with several types of point and the choice of size and point type is determined by the fabric to be sewn.
The three categories are as follows.
Within this category is the set cloth point used for sewing woven fabrics; the point is slightly rounded which displaces the yarns of the material being sewn without damaging them. The slim set point is an acute point which is used in the Single Thread Chainstitch Blind stitch (103) machine for hemming fine to densely woven fabrics.
The heavy set point or stub point is used in button sewing machines. The blunt point will safely deflect the button into the correct position to enable the needle to pass through the holes in the button.
Ball points are available in three weights, light, medium and heavy, and are used for sewing knitted fabrics.Ball point needles do not pierce the threads of the fabric but displace the yarns in the fabric. The needle pushes between the fabric yarns rather than cutting or piercing the fabric.
Light ball points are used for sewing lightweight knitted fabrics. Medium and heavy ball points are used for sewing elastic fabrics containing rubber or elastomeric yarns; this needle point does not perforate the elastic yarns but pushes them aside.
This category of needle is used for sewing leather and coated or laminated fabrics. These are classified and named according to the position of the cutting edge and its shape. The shape of this needle will create a slit (rather than a large hole) through which the thread will pass.
The fabric weight determines the size of the needle and thread to be used. When sewing fine fabrics both the needle and thread should be small in diameter. There are two needle sizing systems: the Number Metric and Singer system.
Needles are commonly labelled with two measurements separated by a slash. The Number Metric system simply gives the diameter of the needle in millimeters multiplied by 100; for example, a standard ‘80’ needle is 80 mm in diameter. The second number refers to the Singer system; for example, an 80/12 needle is simply the same needle measured by the two different systems.
The table below is a guide indicating the needle size and the stitch length for sewing a range of fabrics:
Choosing the correct thread is fundamental; perfectly matched threads are often inconspicuous in a seam and, as a result, too little attention is paid to the choice of thread. The cost of thread contributes only a small fraction to the overall cost of the garment, but if a poor sewing thread is selected it can increase production costs significantly owing to frequent thread breaks.
When selecting the correct thread consider the following:
➾ fi bre contents
➾ performance of the thread during the sewing process
➾ performance of the thread in the completed garment during its lifetime in wear and cleaning
➾ thread package
Like other textile materials, sewing thread can be made up from diff erent fi bre types, constructions and finishes and each can influence the appearance and performance of the seam. Many thread sizes (thicknesses) are available and the choice of size is determined by the requirements of the fabric and product, which, in turn, determine the size of the sewing needle; for example, a blouse made from a fine satin fabric will be sewn with a fine thread, 180 thread and a 70/10 size needle. A leather bag will be sewn with a heavy, strong thread, 75 thread and a 90/14 size needle.
Threads from natural fibres include silk threads spun from a continuous filament or broken filament. This thread is strong with a lustrous appearance and it performs well in the sewing machine but it is costly. The high cost restricts its use to sewing buttonholes and topstitching on bespoke tailoring, haute couture garmentsand specialized embroidery.
Linen threads are spun from fl ax that produces an extremely strong thread used for stitching footwear, leather products and attaching buttons. Linen threads have been largely superseded by synthetic threads, which are also extremely strong.
Cotton is also constructed by spinning the longest cotton fibres. It has good sewing performance but the strength and abrasion resistance are inferior to synthetic threads. Cotton threads can also shrink when wet, causing pucker. Cotton threads are generally less affected by needle heat.
Threads from synthetic fibres are popular today; they do not rot and they have greater strength for their size with low shrinkage.
Polyester and Polyamide (nylon 66) are both formed by melting chips of polymer and extruding the molten polymer through a spinnerette, which is then cooled and collected to form yarn. The yarns are then stretched and crimped to produce a better frictional surface and either cut or stretched to produce lengths of fibre, which are spun into thread.
Thread made from spun yarns generally has:
➾ Good sewing performance
➾ Good dimensional stability
➾ Good stitch locking properties in the seams because of the fibrous surfaces
➾ Abrasion resistance depending on the fibre
Alternatively, continuous multifilament yarns go through a process of imparting texture to the yarn which gives it a softness and bulk; this thread is commonly known as bulked thread. It is used extensively in the loopers only of Overedge, Multi-thread Chainstitch and Covering Chainstitch machines, as it gives a soft handle or feel to the seam with maximum seam coverage.
Viscose is used for embroidery only. Viscose threads have poor strength and durability.
Corespun thread has a continuous fi lament core wrapped with a sheath of spun fi bre. The continuous filament synthetic core is strong and the spun fibre on the outside enhances the sewing properties. Corespun thread is strong but fine with good stretch properties and low shrinkage. Corespun threads enable adequate seam strength with finer thread, which means a finer size needle can be used.
Measure the seam lengths in the garment and equate them to the stitch consumption rates below:
There are a number of systems used for indicating thread size: the Metric Count, Cotton Count and Denier Systems use ticket numbering systems to give an easy approximation of the specific size of the finished thread. The Metric Ticket Number system is the most common sizing system used universally. All thread sizing systems are based on length and weight, the general rule being the higher the thread number, the finer the thread, the lower the ticket number, the thicker the thread. The table below indicates the thread
size to be used for particular applications.
Thread is available in different packages. Spools carry short lengths of 100 to 500 meters of thread and are used mainly in domestic sewing.
Cops carry 1000 to 2500 meters.
Cones carry 2500 to 5000 meters of thread and are the most economical to use in situations where thread consumption is high.
Vicones hold polished and continuous fi lament threads. The raised flange at the bottom is designed to prevent the thread from slipping off at the bottom.