49: SAFETY-STITCH SEAM PROBLEMS

Whether or not you sew, knowing something about sewing makes one a better shopper. This post is about why it's important to take a look at the seams when trying on clothing in the stores. The post discusses safety-stitching, how/why it is used to manufacture garments, and problems that one might encounter in garments made with this method of construction.

Safety-stitching sews the seams
and finishes the edges in one operation.
If the seams breaks, the overcast edge will prevent the
garment from opening, which is why it is called a
safety-stitch.

Below is some information about how safety-stitch seams are sewn. Safety-stitching is a very fast way to sew seams as seams are both sewn and overlocked in one operation. These machines make it possible for industry to sew garments, such as t-shirts, together in 5 minutes or less. An advantage of safety-stitching is that if the seam breaks, the overcast edge will prevent the garment from opening, hence the name safety-stitch.

Safety-stitching is a good choice when sewing bias garments because the stitching has considerable recoverable stretch. But safety-stitching is much more often used to produce garments that are best described as cheap. 

Although operators overseas have tremendous hand-skills and can sew at the speed of lightening, they must sew as they are told. Manufacturers want to make as large a profit as possible. Here in the USA we pay top-dollar, often for inferior products. These products are made by overseas operators who get paid very little to produce garments that are often very poorly made. Everyone looses.

When one discovers that a sewn garment has flaws it needs to be returned to the store. The store then returns the garment to the factory, as this is the factory's problem. It is important that we return inferior products. If we accept inferior products that is what the factories will make. 

1: Lockstitch sewing machines have bobbins.

1: Lockstitching is produced by sewing machines that have bobbins (diagram 1).

Lay people usually call lockstitching straight stitching, Straight stitching is a term that can be applied to a number of straight stitch types, the reason the industry uses the term lockstitching.

2: Overlock sewing machines have loopers.
Home sewers call overlock machines sergers.

2: Overcasting and chain stitching are produced by overlock sewing machines that have loopers (diagram 2).

3: Safety-stitching with a lockstitched seam. 

Safety-stitch machines sew the seam, while 

simultaneously overcasting the edge of the 

seam This is a good choice when sewing woven

fabrics, but not when used to sew knits as it is 

unlikely that the lockstitched seam will have 

as much stretch as the knit fabric, and therefore

the lockstitched seam may break fairly easily.

4: Safety-stitching with

 a chain seam, the better choice 

when sewing knit fabrics

3. Safety-stitch machines sew the seam, while simultaneously overcast the edge of the seam (diagrams 3 and 4).

4. Some safety-stitch machines sew the seam with a lockstitch. These machines have a bobbin  (diagram 1) that interacts with the machine’s needle as the seam is sewn. They also have a looper  (diagram 2) which interacts with a second needle to simultaneously overcast the edge of the seam (diagram 3).

Safety-stitch machines that sew their seams with lockstitching are a good choice for sewing woven fabric at top speed. But they are a poor choice when used to sew knits. The lockstitched seam will not stretch with the knit fabric, often causing the seam's thread to break.

Chain stitching requires slightly more thread than lockstitching. That is why manufacturers may try to save a little money by sewing knits with these machines. The little bit of thread saved adds up when multiplied by a thousand garments.

5. Other safety-stitch machines sew the seam with a chain stitch. These machines have a looper that interacts with the machine’s needle  as the seam is sewn. They also have a looper which interacts with a second needle to simultaneously overcast the edge of the seam. These machines are a good choice for sewing knit fabric because both the chain stitching and the overcasting provide stretch. The stitching is compatible with knit fabric (diagram 4).

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