Sewing Machine Needles: Types, Parts, Sizes, and Applications
Sewing Machine Needle and Its Purposes:
A needle is the central feature of any sewing machine. The manner in which fabric is pierced by the needle during stitching has a direct impact on the strength of the seam as well as garment appearance.
The purposes of the sewing needles are to:
- Make a hole in the fabric so that the sewing thread could pass through it to form a stitch without causing any damage to the fabric while doing so.
- To carry the needle thread through the fabric to form a loop. This is then taken up by the hook in a lockstitch machine or by means of the looper in chain stitch machines.
- Pass the needle thread through the loop created by the looper mechanism on a chain stitch machine.
Every part of the sewing machine needle are described below:
Shank is the top portion of the needle, which positions inside the needle bar. It could be designed as cylindrical or have a flat side, based on the method of holding it on to the needle bar. It is the principal support of the entire needle and is larger in diameter than the remaining part of the needle to give the strength.
It is the part in-between the shank and the blade, with the blade forming the longest portion of the needle up to the needle eye.
It undergoes an enormous amount of friction from the fabric through which the needle passes. In the case of needles specifically designed for high-speed sewing, the shoulder is normally extended into the upper part of the blade to give a thicker cross-section. This arrangement of a reinforced blade strengthens the needle and produces the enlarged hole in the fabric while the needle is at its lowest point, thus minimizing the friction between it and the material. On the other hand, the blade could be designed as a tapered one, reducing its diameter gradually from shank to tip to minimize the friction.
It gives a shielding channel for the sewing thread while it is carried down into the fabric for stitch formation thus reducing the abrasion and friction with the fabric.
The short groove is located on the reverse side of the long groove, that is, towards the hook or looper; it extends slightly above and below the needle eye. It assists in the formation of the needle thread loop.
It is the hole or opening in the sewing needle, lengthened through the blade along the long and short grooves on the needle. The profile of the inside part of the eye at the top is vital in reducing sewing thread damage and in producing a good loop formation.
The scarf otherwise known as clearance cut is a nook across the whole face of the needle immediately above the needle eye. Its objective is to facilitate the closer setting of the bobbin hook or looper to the needle so that the needle thread loop could be entered more easily by the point of the hook or looper.
It is a tapering portion of the needle created to give better penetration of the needle on various kinds of fabric. It should be properly selected to prevent damage to the fabric to be sewn.
Tip: It is the ultimate end of the point, which combines with the point in defining the penetration performance of the needle.
Several over-edge and safety stitch sewing machines utilize curved needles instead of straight needles. These needles are costly though the life of the needle is lesser compared to straight needles. However, the sewing machines utilizing curved needles (Figure-2a) could achieve higher speeds than by using straight needles. Blind stitching machines also utilize needles that are curved, but the purpose here is to avoid penetration right through the fabric. Sewing machines (pick stitching machine) that imitate hand stitch (class 209) utilize a double-pointed sewing needle with an eye in the middle (Figure-2b), through which is threaded the short length of thread with which this machine sews.
Identification of Sewing Needle:
Three parameters are generally used for the identification of sewing needles such as system, point, and size.
It describes the elements of a needle to suit the sewing machine type. Based on the type of sewing machine and type of stitch, the needle is designed with variants in blade length, shank thickness, type of needle eye, etc. It is worthwhile to ensure with the sewing machine manufacturer for appropriateness of needle system to the machine.
A needlepoint is broadly categorized into two types:
- Round point needle – set or cloth points
- Cutting or leather point needle
Cutting Point Needles:
These sewing needles have spiky tips like blades and a wide range of cross-sectional profiles such as rounded, triangular, square and lens exist. They are normally used to sew highly dense and non-fabric based materials. Five universal kinds of cutting point sewing needles are shown in Figure-3, along with their profile of incision produced when used in a machine with the commonest threading direction.
The narrow wedge point needle: It cuts the material at right angles (90°) to the seam direction and permits to go for a high stitch density (SPI) while leaving adequate material between the needle holes to retain seam strength of the material. On soft leather material, stitch densities as high as 12 per centimeter are achievable. It is the most frequently utilized cutting point needle for stitching uppers in the shoe industry.
- The narrow reverse point needle: It produces cut that lies 45° to the seam direction, and produces a seam where the thread is turned to the left on the surface of the material.
- The narrow cross point needle: It makes a cut along the line of the seam and necessitates a longer stitch length. Heavy decorative seams could be made where thicker sewing threads are used at lower stitch densities, that is, longer stitch length.
Numerous kinds of other point types exist for the variety of leathers, seams, sewing machines and strength and appearance requirements that arise. This involves triangular cross-sections for multi-directional sewing.
Cloth Point Needles:
These kinds of needles are used for sewing textile materials instead of the leather/sheet materials as in the case of cutting point needles. The points have a round cross-section contrasting to the various cutting profiles of the cutting point needles and the tip at the end of the point can vary in profile to suit the particular material being sewn.
- The contour of the tip of the needlepoint which attains the deflection rather than penetration is a fine ball shape and the needle is called a light ballpoint needle which is utilized primarily for sewing knitted fabrics.
- The tip of the needlepoint which attains the penetration has the shape of a cone and is known as a set point needle that is utilized for sewing woven fabrics. Both ball and setpoint needles are available in a number of types.
Slim set point (SPI):
It is generally used for sewing denser woven fabrics and aids in achieving a straighter stitch which could minimize seam pucker. Generally used for heavy woven fabrics, coated fabrics and topstitching of collars and cuffs.
Medium set point needle:
It is the general-purpose needle in no problem sewing situations. It is commonly used for sewing a range of woven fabrics. In many circumstances could be used for knitted fabrics also.
Set cloth point (R):
It is generally utilized for sewing standard fabrics with regular seams.
Acute set point:
This kind of needle is used while sewings very dense fabrics such as shirting fabric and interlining in collars and cuffs, where a straight line of stitching is required.
These needles are used for sewing buttons as the button can be deflected to some extent into the correct position; thus, the needle can pass through the holes.
Light ballpoint (SES):
It can be used for sewing lightweight knitted fabric and densely woven material.
Medium ballpoint (SUK):
It is utilized for sewing denim fabrics of medium to coarser weight and knits.
Heavy ballpoint (SKF):
It is utilized for sewing heavier woven elastic materials as well as coarser knits.
Special ballpoint (SKL):
It could be utilized for sewing heavy knits and coarse elastics.
The needle size is normally expressed in two ways. One of the basic methods of representation is by a metric number (Nm). This system represents the diameter of the needle blade in hundredths of a millimeter measured just above the scarf area. For example, a needle size of Nm 100 is 1.0 millimeters in diameter as shown in Figure-5. Another standard needle sizing method is the Singer system (American system), which uses a number that represents a size.
Needles are offered in a wide range of sizes. The selection of needle size is based on the combination of fabric and sewing thread which is to be sewn.
If the selected sewing needle is too small for the sewing thread size, the thread will not fit well into the long groove of the needle. It will suffer from extreme abrasion. The use of too fine a needle while sewing heavy plies of fabric could lead to the deflection of the needle. Which in turn influence the stitch loop to pick up and cause skipped stitches or even needle breakage. The use of a larger sewing needle for the particular sewing thread resulted in poor control of the loop formation which could lead to slipped stitches.
Surface Finishing of Sewing Needles:
Sewing needles are normally made from steel. During their final manufacturing stage, they are polished, specifically in the needle eye area. They are then electroplated using chromium or nickel to provide resistance to mechanical wear, corrosion resistance, and reduction of friction during sewing. The surface finishing of needles should not pick up elements of fabric or thread which may melt due to excessive heat. By considering this aspect, the chromium-plated sewing needles are superior compared to nickel-plated needles.