Industry Technologies
In the previous issue of The Needle's Eye, we discussed the system devised by the Federal Specifications Board. We focused primarily on stitches. In the second part of this two-part article, we turn our attention to the classification of seams and stitchings.
What is a seam or a stitching? A seam may be defined as a series of stitches used to join two or more plies of material. Most apparel operations are grouped under a seam classification. A stitching, on the other hand, is a series of stitches used to finish the edge or for decorative purposes on a single ply of material. Serging and hemming operations are common examples of stitchings. It is important to remember not to confuse stitchings with stitch type classifications.
The federal specifications booklet divides seams into four classes: Superimposed Seams (SS); Lapped Seams (LS); Bound Seams (BS); and Flat Seams (FS). Stitchings are divided into two classes: Edge Finish (EF) and Ornamental Stitchings (OS). Within each of these classes are several types which are indicated by lowercase letters, such as SSa or LSb.
Superimposed Seams
Superimposed Seams (SS) are produced by sewing together two or more plies of material, with the edges of the materials generally being even. This is accomplished with a simple sewing machine edge guide or, occasionally, with a more complex folding device. Sixty superimposed seam types are classified for various operations.
SSa, probably the easiest seam to form, is the most common of all the seam types used for apparel. One ply is placed on top of another with the edges kept parallel by a material trimmer, edge guide, or seam guide. Main seams on slacks, shirts, jackets, coats, vests, and draperies - to name a few - are formed with this seam type. The first operation in making shirt collars or cuffs, pocket flaps, and other runstitching operations are usually done with this seam. Seam type SSa is commonly formed with 101, 301, 401, 502, 504, 512, 514, 515, 516 and 519 stitch types.
SSc is formed by folding both the top and bottom edges toward each other by hand or with the aid of a creasing machine. This seam is used to produce cuffs and flaps on coats, shirts, jackets, etc., in one operation. This seam is usually produced with a 301 lockstitch because it appears the same on the top and bottom sides.
SSd is formed by folding the top and bottom plies in opposite directions. Manufacturers have found that for jute and burlap bags, this seam is virtually leakproof when the bag is turned right side out. Bag manufacturers use a 401 stitch with this seam.
SSe (a & b) consists of an SSa seam (a) that is folded over and topstitched with another row of stitches (b). Combined, this seam and stitch form the SSe seam, used for runstitching and topstitching collars, cuffs, flaps, pockets, and facings on a wide variety of garments. Because this seam is formed in two operations, the number of rows of stitch indicated after the seam type represents both operations.
SSh (a & b), requiring two operations, is used on knitted garments where the first operation is usually sewn with a 504 overedge stitch (a), and the second operation is produced on a 406 stitch coverseaming machine (b). Combining the excellent elasticity and coverage of these two stitch types, a very durable seam is formed for use on swimwear, sweaters, sportswear, and children's clothing.
SS1 (a & b inverted) is formed by inserting a ply of material into the hem of another ply (a). An inverted construction of this seam is commonly used for setting pockets to jeans (b). One or two rows of 301 lockstitches, with the same, neat appearance on both sides of the material, are used for this operation. This allows the operator to sew from the inside of the garment where she can more easily see where she is placing the pocket. Attempting to perform this inside-out sewing operation with a chainstitchtype stitch would result in the looper thread appearing on the outside of the garment. SSn and SSp are used to seam materials that ravel or fray easily. Both the top and bottom plies are folded once or twice producing a very secure seam for use on ladies' and children's dresses, pajamas, nightgowns, hosiery, and mesh bags.
SSn and SSp are used to seam materials that ravel or fray easily. Both the top and bottom plies are folded once or twice producing a very secure seam for use on ladies' and children's dresses, pajamas, nightgowns, hosiery, and mesh bags.
Lapped Seams
Lapped Seams (LS) are formed by joining two or more plies of material that are overlapped at the needle. Most of the seams produced in this class require some type of folder to aid the operator in forming the seam. 108 different lapped seams types make this the largest seam classification.
LSa, although one of the easiest seams to form, is seldom used in the construction of woven goods because of the raw edges that are vulnerable on both sides of the seam. Its use is confined to joining selvage edges, such as in the construction of awnings and tents. For knit goods, however, this seam is commonly used with a coverstitch to produce very flat and elastic seams. The cover thread on the top and the looper thread on the bottom prevent the edges of the material from raveling. Usually, an edge guide is used to position the bottom ply, and a special presser foot with a yielding section is used to position the top ply.
LSb is formed by turning the edge of the top ply under, thus forming a semi-felled seam. When used for main seams on coats and jackets, the finished edge is on the outside, while the raw edge is concealed on the inside. This seam is produced with either a 301 lockstitch or a 401 chainstitch.
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LSc, known as the "felled" seam, is the strongest of all the seam types. Both top and bottom edges are folded in such a way that they interlock, leaving no raw edges. In 1896, Union Special Corporation designed the first adjustable folder for this seam for use on multiple needle machines producing stitch type 401. Today, the LSc seam is used in the construction of jeans, jackets, shirts, pajamas, coveralls, shorts, tents, and parachutes.
LSd, although seldom used for main seaming, is used to set most patch pockets, pocket flaps, pocket facings, and labels. To aid in the handling of the material, the edges of pockets, labels, etc., are occasionally creased prior to the seaming operation, giving greater uniformity and improved appearance.
LSe is formed by inserting a third piece between two folded plies. This seam allows an operator to join the shoulders or set the cuffs of a dress shirt in one operation. A 301 stitch is generally used on this operation since it looks the same on both sides.
LSf (a & b), used on shirts, dresses, and blouses for yoking operations, is usually joined with a 401 stitch (a) where the looper thread is completely hidden on the inside of the garment (b).
LSk is used for taping operations on brassieres, attaching button facings to shirt fronts, and waistbanding operations. A body folder and a lower or upper strip folder are used to make this seam with two or more rows of stitches. LSm, called a "Tru-front" or "seton" centerplait, is used in the production of fronts of shirts, blouses, leisure suits, and pajamas with two or more rows of 401 stitch. The "center plait" seam is similar to the LSk seam, except that an interlining strip is added.
LSq (a & b) consists of an SSa (a) seam which is folded open and restitched (b), thus combining a strong seam with a neat appearance. This seam is occasionally used on the sides of slacks, to set sleeves on shirts and blouses, and on other operations requiring a flat seam. Because this seam is formed in two operations, the number of rows of stitch indicated after the seam type represents both operations.
Bound Seams
Bound Seams (BS) are one of the best means of finishing the raw edge of an article with a neat and tailored appearance. A bound edge seam is made by folding a piece of material around the edge of another, usually with the aid of a binder. 18 bound seams are classified in the federal specifications, with the type of binding and the seam type directly related to the stitch type being used.
BSa is formed by folding the binding around another ply of material, leaving the raw edges of the binding unfinished. When using a 301 or a 401 stitch with this seam, a selvage edge binding or binding made of paper or plastic is necessary. When this seam is produced with a 602 or a 605 coverstitch, the looper thread on the bottom and the spreader thread on the top cover these raw edges producing a very flat seam. The BSa seam is used to close the tops of bags, to set collarettes to undergarments, and to finish the edges of sheets and pillowcases.
BSb, requiring a less expensive cutedge binding, combines the neat and tailored appearance of a finished edge on top with a flat, smooth seam on the bottom. Sewn with a 406 stitch, this seam is used to bind the edges of undergarments and similar garments with a ribbed or flat knit binding.
BSc, referred to as "piping" a raw edge, is formed with a cut-edge binding and can be sewn with either a 301 lockstitch or a 401 chainstitch. This seam is used to bind the edges of overcoats, jackets, aprons, dresses, and upholstery. The top and bottom edges of the binding are folded, thus giving a clean, finished appearance on both sides. Today, most jeans manufacturers use this seam to attach the waistband to the body in one operation.
Flat Seams
Flat Seams (FS) are produced by butting two plies of material together, usually with a 606 or 607 coverstitch. Flat seams are used primarily in the construction of undergarments, foundation garments, sportswear, and sleepwear to provide comfort.
FSa is the simplest of the flat seams and is usually formed on a machine that trims both edges before butting them.
FSf (a & b) is formed in two operations and is used for bolt end seaming large pieces of material. The two plies are sewn together with an overedge stitch forming seam type SSa (a). They are then hinged or folded open forming a flat seam (b) that can easily be fed through dyeing and finishing equipment.
Edge Finish Stitching
Edge Finish Stitching (EF) is used primarily to finish the edge of a single ply of material rather than to join the plies of material. There are 34 stitching types in this class used for serging and hemming.
Efa (a & b inverted), formed by turning the edge of a single ply of material, is used to hem a selvage edge or to prepare a garment piece for a subsequent operation (a). An inverted construction of this stitching is commonly used in knitted robes, sportswear, and undergarments in conjunction with a 406 stitch (b). The looper thread on the bottom covers the raw edge and prevents it from unraveling.
EFb is used to hem the edges of shirts, jeans, and raincoats where the raw edge is locked inside the hem giving a clean, finished appearance. A hemming folder or hemming presser foot is generally used to form the material on a 301 lockstitch or a 401 chainstitch machine.
Efc (a & c) is used to blind hem the sleeves and bottoms on knit garments such as T-shirts. By folding the edge of the material in a certain manner when it is sewn (a), a blind stitch effect is produced (b).
EFd, the simplest edge finish stitching, is formed with a row of 503, 504, or 505 stitches. Referred to as "serging", type EFd is used on slacks, shirts, dresses, jeans, draperies, and upholstery.
EFh is the stitching most commonly used to make belt loops for jeans or work pants. Usually formed with a 406 stitch, the looper thread on the bottom covers the raw edges.
Ornamental Stitching
Ornamental Stitching (OS) is used for decorative stitching operations on single plies of material. Quilting operations on upholstery, bedspreads, etc., are usually performed using an OSa stitching sewn with a 301 lockstitch.
This concludes the brief examination by The Needle's Eye of the system for classifying stitches, seams, and stitchings.
