Class 2: Lapped Seam

The simplest seam type in this class is formed by lapping two pieces of material.

These seams are produced with a minimum of two pieces of components. One component is limited on one end and the other is limited on other end.

 In practice, this simple seam is not common in clothing because it causes problems with raw edges and at least one of the edges must be neatened in a decorative manner. 

Much more common on long seams on garments such as jeans and shirts is the so-called lap-felled seam, sewn with two rows of stitches on a twin needle machine equipped with a folding device. This provides a very strong seam in garments that will take a lot of wear, though there is a possibility that the thread on the surface may suffer abrasion in areas such as inside leg seams.

The type of raised, topstitched seam is also technically a lapped seam, although at the beginning of its construction it appears to be a superimposed seam. It is often referred to as a welted or a raised and welted seam.

Class 3: Bound Seam

The seam is constructed by binding a component end with another narrow component.

The seam is produced with minimum of two pieces of component. One component is limited on one end and the other component is limited on both ends. 

The simplest version of this class is again unusual as it cannot be constructed with self-fabric binding because of the problem of raw edges. It can, however, be made with a binding that has been constructed to a specific width or a contrasting colour of the garment fabric, has been cut into narrow strips.

A folding device can be used which folds the edges of binder and wraps the edge of the main fabric. A bound seam is often used as a decorative edge. 

Examples in common use on underwear and leisurewear and on skirts, jeans and ladies’ trousers are shown in figures.

In part (i) is shown a common finish used on the neck edge of tee shirts, and also on the edges of men’s vests and briefs.

 In Fig (ii), there is an insert of another cut strip. This would normally be in a contrasting color to the garment and both could contrast with the outer binding.

In Fig (iii), elastic has been included in a sufficiently stretched state to draw the edge of the garment in to a snug fit.

 On all these seams, a stitch type would be used which has two needles and incorporates a thread passing between the needle threads on the underside and covering the raw edge of the fabric. 

In Fig. 3.11(iv), a waistband, usually with an interlining fused to it, is bound on to the top of a skirt, jean or trouser using a folder and twin needle machine. The ends of the waistband require stitching separately.

Class 4: Flat Seam

In this class, seams are referred to as flat seams because the fabric edges do not overlap. 

They may be butted together without a gap and joined across by a stitch which has two needles sewing into each fabric and covering threads passing back and forth between these needles on both sides of the fabric. 

Knitted fabrics are most commonly used because the advantage of this seam is that it provides a join that is free from bulk in garments worn close to the skin, such as knitted underwear.

The machine trims both fabric edges so that they form a neat join. Alternatively, various zig-zag stitches could sew back and forth between the fabrics which might then have a decorative gap between them.

Class 5: Decorative Seam

This is the first of the two classes of seam which, in the old British Standard, were not regarded as seams at all and were given the name stitching’. 

The main use of the seam is for decorative sewing on garments where single or multiple rows of stitches are sewn through one or more layers of fabric. These several layers can be folds of the same fabric. The simplest seam in the class has decorative stitching across a garment panel. One row would have little effect but multi-needle stitching is common. 

Figure (i) shows twin-needle stitching with a ribbon laid under the stitches while part (ii) shows four rows of stitches. 

Other possibilities, given by the right folding devices, are pin tucks, often sewn in multiples, and channel seams. These are shown in Fig (iii) and (iv). This type of pin tuck is different from the traditional version, which consists of a fold in the fabric sewn close to the edge. When multiple, parallel tucks are required, the original method is slow and potentially inaccurate. In the version shown here, the folder ensures the tucks are parallel as all the tucks are sewn simultaneously. The tucks must, however, be set to face one way or the other and a decision as to which must be made in relation to the design of the garment.

Class 6: Edge Neatening

This is the other seam class that was previously called a stitching. Seam types in this class include those where fabric edges are neatened by means of stitches (as opposed to binding with another or the same fabric), as well as folded hems and edges. 

The simplest is the fabric edge inside a garment which has been neatened with an overedge stitch, as shown in Fig. 3.14. In considering hems on the sleeves and lower edges of garments, there are many possibilities when the variety of stitch types that can be used is taken into account. A selection is shown in Fig. 3.15,

 In Fig. 3.15, (i) is typical of the hem on a dress or a pair of trousers in a woven fabric, which has been neatened and then sewn up invisibly (blind stitched). In a knitted fabric the neatening might be omitted.

 In (ii), a folding device is used in the construction of the hem of a shirt or a skirt lining; (iii) and (iv) show a method of folding an edge that is sometimes used on the buttonhole front of a shirt. Two different constructions are possible, the first one requiring the sewing to be done in two stages, the second one requiring a twin-needle machine. 

The remaining two seam classes in the 1991 British Standard are an addition to the original standard, added in the 1983 edition, to include seam types commonly seen in modern garment construction. No general descriptive title has been given to either of them.

Class 7

Seams in this class relate to the addition of separate items to the edge of a garment part. They are similar to the lapped seam except that the added component has a definite edge on both sides. 

Examples would be a band of lace attached to the lower edge of a slip as in Fig (i), elastic braid on the edge of a bra as in (ii), and inserted elastic on the leg of a swimsuit as in (iii) 

An example where the additional item is self-fabric plus interlining is another version of the buttonhole band on a shirt, shown in Fig. 3.17. This is another instance where, by using two folders and a twin-needle machine, a complicated construction can be completed in one step. Without such machinery, achieving a similar, let alone identical, result would be very diffi cult.

Class 8

The final seam class in the British Standard is another where only one piece of material need to be involved in constructing the seam.

The commonest seam type in this class is the belt loop as used on jeans, raincoats, etc. This is shown in Fig.(i). Also included in this class are belts themselves; two possible constructions for these are shown in Figs (ii) and (iii). The use on the belt loop of the stitch type mentioned before, which has two needles and a bottom covering thread, ensures that the raw edges are covered over on the underside while showing two rows of plain stitching on the top. The belt shown in (iii) is quicker and cheaper to construct than the one shown in (ii) but, as always, a special machine attachment is required to fold the fabric. 

Reference: Technology of Clothing Manufacture by Carr & Latham