Types of Seam

Seam Types

A formal description of the configuration of a seam is called seam type.

Seam Classes

1. Class 1 – Superimposed seam
2. Class 2 – Lapped seam
3. Class 3 – Bound seams
4. Class 4 – Flat seams
5. Class 5 – Decorative/Ornamental stitching
6. Class 6 – Edge finishing/neatening
7. Class 7 – Attaching of separate items
8. Class 8 – Single ply construction

Class 1 – Superimposed seam(s)

These generally start with two or more pieces of material superimposed over each other and joined near an edge, with one or more rows of stitches. There are various types of seams within this class.

Stitches Used

Stitches Used A superimposed seam can be sewn with Stitch Types 301 or 401 to create a simple seam. The same seam type can also be sewn with Stitch class 500 (Over edge stitch) or Combination stitches (e.g., Stitch class 516)

Application
used to create neat load bearing seams for lingerie, shirts, etc.

Class 2 – Lapped seam(s)

In this class of seam, two or more piles of material are lapped (i.e., with edges overlaid, plain or folded) and joined with one or more rows of stitches.

One of the most popular of this class is the Lap felled type, involving only one stitching operation – a strong seam with fabric edges commonly used to protect jeans or similar garments from fraying. The superficially similar French seam type involves two stitching operations with an intervening folding operation – a flat, folded seam with only one row of stitching visible on the top surface.

This seam class consists of a minimum of two components and can have different varieties consisting of a number of rows of stitching.

Stitches Used
The lap felled seam is generally sewn with a 401 chainstitch.

Application
The looped seam is the most commonly used seam. It is used in jeans manufacture because of its strong construction. The French seam is commonly used for rain wear, and edge stitching front facings on jackets and dresses.

Class 3 – Bound seam(s)

These are formed by folding a binding strip over the edge of the piles of material and joining both edges of the binding to the material with one or more rows of stitching. This produces a neat edge on a seam exposed to view or to wear. There are a variety of bound seams.

Stitches Used
401 chain stich or 301 lockstitch

Application
Necklines of t-shirts

Class 4 – Flat seam(s)

In these seams (sometimes called Butt seams), two fabric edges, flat or folded, are brought together and over sewn with stitches.

The purpose of these seams is to produce a joint where no extra thickness of fabric can be tolerated at the seam, as in underwear or foundation garments. The looper thread(s) must be soft, yet strong and the cover thread may be decorative as well as strong. This seam is referred to as a flat seam because the edges do not overlap one another, they will be butted together.

Stitches Used
Zigzag lock stitch, chain stitch or covering stitch (class 600).

Application
This type of seam will consist of two components and can be seen on very fine knitted garments where seams are required to be free from bulk.

Class 5 – Decorative/Ornamental stitching

The ornamental stitch is a series of stitches along a straight or curved line or following an ornamental design, on a single ply of material. More complex types include various forms of piping, producing a raised line along the fabric surface.

Application
The stitching results in decorative surface effects on the fabric e.g., pin tucks, application of braids, etc. This seam type consists of a minimum of one component.

Class 6 – Edge finishing/neatening

Edge finishing stitch is where the edge of a single ply of material is folded or covered with a stitch. The simplest of these operations is Serging, Type 6.01.01, in which a cut edge of a single ply is reinforced by over edge stitching to neaten and prevent fraying. The seam class must include seams whereby the edges are neatened by means of stitches and can be used in cases where the raw edge requires finishing. There is only ever one component to this type of seam. This includes other popular methods of producing a neat edge like hemming and blind stitch hemming.

Application
Serging trouser panels, flys, facings, etc.

Class 7 – Attaching of separate items

This seam class involves seams that require the addition of another component onto the edge of a piece of fabric e.g., elastic braid onto the edge of ladies briefs. This type of seam requires two components.

Class 8 – Single ply construction

This seam class consists of one piece of fabric that is turned in on both edges. It is most commonly seen in belt loops or bets for which a folder can be attached to the machine. This type of seam requires only one component.

Seam Quality 

Though the stitch types chosen for a seam depend on the functional or aesthetic requirements of the seam, seam quality can be measured based on the following parameters:

• Seam size
  It is measured with seam depth, seam length and seam width.
• Seam slippage strength
  It is the amount of force required to pull out a total of ¼” of the opposing sets of yarns perpendicular to the seam line.
• Seam strength
  It is the force required to break open the seam either by breaking the thread or by breaking the sewn material.