SEWING THREAD CONSTRUCTION 1 COTTON THREAD

Cotton fibres are aligned and twisted together in S direction to form a single yarn. Two more single yarns are ply-twisted in reverse direction (Z direction) for twist balancing and to eliminate snarling.

20.6.2 SPUN SYNTHETIC

The fibres used for spun synthetic threads are normally polyester staple fibres similar to cotton. Heat setting is required to control their shrinkage and extensibility. Their higher strength and abrasion resistant compared to cotton threads are advantageous. They are available in a wide variety of colors and sizes. Spun polyester thread is one of the most widely used threads and is least expensive.

20.6.3 MONO-FILAMENT

When threads are made directly from continuous filaments as in polyester and nylon, we can have a single filament having larger size than normal. This is called as mono filament. Its normal co lour and translucent appearance blend with the color of most fabrics. It is strong and more uniform so breakage during sewing is minimal. It is too stiff and place excessive wear on machine parts. Its holding power is limited and tends to unravel from the seams. Its use is limited to stitching of hems in low budget garments, draperies and upholstered furniture.

Flow chart manufacturing spun sewing thread

20.6.4 MULTI-FILAMENT

This is the most conventional way of constructing continuous filament sewing threads. They can be either in singles or plied or corded. They are popular because of better utilization of fiber strength, low fault rates and a consistent, even thread at reasonable cost. They are invariably used where strength of the steams is a primary requirement such as sew shoes, leather garments, tents, awnings and boat covers.

20.6.5 CORE SPUN

To combine the advantage of both the synthetics ad naturals, we can have continuous filament polyester wrapped around with a sheath of cotton fibres. This thread structure gives the strength of filament polyester and sew abilities of cotton. However careful dyeing is needed to obtain the same shade on both sheath and core, which requires two dye baths. Polyester or

Streaming (Heat setting) Store of single yarn

Hank dyeing to the require shade Wet Doubling yarn

Reeling yarn

Rewinding

Singing (or) Gassing

Waxing & polishing

Precision Winding

Article no. of assignment & packing

Package Dyeing

viscose rayon or cotton may be used as sheath. Polyester wrapped core spun thread is subject to needle heat and may not be desirable in terms of co lour. Cotton wrap is most widely used core spun threads are costlier and have high strengths than spun polyester threads.

20.6.6 TEXTURED

Various types of textured yarns can be used as sewing threads. These yarns overcome the main drawback of smooth and slippery flat filament yarns. Threads made from airjet textured yarn are used for heavy applications such as furniture and jeans but it has less demanding sewing operations

20.7 TWIST ON SEWING THREAD

The creation of sewing threads from the natural and man-made fibres already described can take a variety of forms. Where the fibres occur naturally in short lengths or have been cut or broken into short lengths, they must be twisted together, initially into a single yarn, and then that twist must be balanced by applying a reverse twist as two or three such yarns are combined to form the thread construction. The twist in the single yarn consolidates the strength and flexibility provided by the fibres themselves. Without the reverse twist, known as finishing twist, a conventional thread could not be controlled during sewing. The individual plies would separate during their repeated passages through the needle and over the sewing machine control surfaces. Twist is defined as the number of turns inserted per cm of yarn or thread produced. If the twist is too low the yarns may fray and break; if too high, the resulting liveliness in the thread may cause snarling, loop knots or spillage from the package of thread.

The frictional forces acting on a thread during its passage through a dewing machine also tend to insert some twist, predominantly in one direction. In a lockstitch machine, during normal straight sewing, the needle and hook tend to insert some Z twist reaches equilibrium as it resists further tightening up of the twist. A thread with an S twist becomes untwisted by the action of the machine and then frays and breaks. Because the lockstitch machine type is the most severe in its handling of thread, the majority of threads intended for use in machine sewing are constructed with a finishing Z twist. There are only a few machines, such as flatlock, for which this is not suitable and special threads, two, three or occasionally four component yarns are twisted together to form 2, 3 or 4 ply thread. Subsequent twisting operations may be used to produce heavier or ‘corded’ thread, with the direction of twist reversing each time.

20.8 APPLICATIONS OF SEWING THREADS

Applications of sewing threads

Fabric Thread

Delicate

Tulle, chiffon, find lace, organza

Fine mercerized cotton Fine synthetic thread Silk

Light weight

organza, jersey, voile, crepe, chiffon, velvet Plastic films

Mercerized cotton Silk

Synthetic thread Medium weight

Satin, fine corduroy, suiting, Knits, deep pile fabric

Mercerized cotton Cotton

Silk

Synthetic thread Medium heavy

Gabardine, tweed, sail cloth, denim coating, vinyl, Furnished fabric, deep pile fabric

Heavy duty mercerized cotton Cotton

Synthetic thread Heavy

Over coating, dungaree, upholstery, canvas fabric

Heavy duty mercerized cotton Cotton

Synthetic thread All weights

Decorative loop stitching

Silk Polyester All weights

Decorative hem stitching

Mercerized cotton Silk

Synthetic thread Synthetic Knit and stretch fabrics

Polyester double knit, nylon tricot, jersey, penne, velvet Nylon Mercerized cotton Cotton Silk Leather

Suede, kidskin, capeskin, lambskin

Mercerized cotton Silk

Synthetic thread