About Sewing Seams, Seam Allowances and Finishes

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Sewing Seams. The Importance of a Well Sewn Seam.

The seam is the basic construction element of your sewn project; therefore, when sewing seams, it's important that they be even and have the proper stitch for the fabric being sewn on. An improperly sewn seam can throw off your entire project so it's important to understand how to to sew a seam.

For a properly sewn seam, the fabric should line up along edges and be pinned at regular intervals to prevent it from moving or stretching. On your sewing machine, stitch length, stitch tension and the presser foot should be adjusted according to the fabric being stitched. Your machine's instruction manual is an excellent source for guidance on this.

The standard seam allowance (which is how far from the edge of the fabric to the needle) is 5/8ths though patterns sometimes designate 3/8ths. Seams are usually sewn with the fabric's right sides together. Check your pattern for specific requirements prior to sewing.

How to Sew and Keep your Seams Straight

It is important to keep your seam lines the same distance from the edge of the fabric when sewing. The throat plate on your machine should have marked guidelines to indicate how far to the needle. A separate measuring guage can also be screwed to the machine near the throat plate. These guages are adjustable (right and left) and also pivot, which is very handy when sewing curves. If it helps you to see where your fabric edge should be, you can place a small bit of masking or other tape 5/8ths of an inch from the needle as a guide.

Now I'm going to spill the beans and confess something to you about sewing seams.

I rarely sew a true 5/8th's inch or 3/8th's inch seam. I find it soooo much easier to use the edge of my sewing foot for my seam measurement rather than the lines on the throat plate. Clear as mud? On the machine I use the most for sewing, I know that when the needle in the middle setting, my stitch line is almost 3/8ths from the edge of the fabric for those few times a narrower seam is called for and when my needle is in the left setting, my stitch line is exactly 1/2" from the edge (which is close enough, what's an eighth of an inch among friends!). As long as I'm consistent with every seam allowance sewn during construction, it all works out just fine.

Trimming Your Seams

Oftentimes, once your seams are sewn, you will need to trim them. This most often occurs in places where a full seam allowance would interfere with the fit. Your pattern will usually instruct you when to trim as you proceed through construction.

Grading Your Seams

Grading a sewing seam is when you cut a seam allowance to different widths in order to reduce bulk in the seam. Your pattern will instruct you when this is necessary.

Clipping and Notching Your Seams

Clipping is used when seams are curved outward so that they will be smoother and lay flatter. Small slits are cut into the seam allowance just up to the stiching line, but not through it. Notching is used when seams are curved inward. Small wedges are cut to remove excess fabric in order for the seam to lay flat.

Understitching

This technique keeps the facing and its seamline from rolling over and being seen on the right side of the fabric. Working from the right side with both the garment and the facing laying smooth and flat (not folded together), stitch on the facing through the facing and seam allowances staying close to the seamline.

Finishing Your Seams

Don’t have a serger? No problem! People were sewing seams and finishing them long before sergers were invented.

Most seams are finished after they have been sewn and pressed open. Make sure the main fabric is out of the way and you are only sewing on the seam allowance.

How you finish your seam will be determined by

The type of fabric you are sewing on. (Does it ravel easily? Is it delicate?)
Will the seams be seen? (such as in an unlined jacket)
How much wear and tear will it receive?

Finishing techniques used when sewing seams.

Edge stitched: Today’s sewing machines have wonderful built in edge stitches which, when used with the edging foot, provides a finish that closely resembles a serged finish. This type of edging also keeps raveling to a minimum and can be used on most types of fabrics. You can edge stitch each seam allowance side or edge stitch them together as one.

Clean finished: Turn under the edge of each seam allowance and stitch along the edge of the fold. This gives a neat tailored look and is suitable for light to medium weight fabrics.

Pinked: Cut the edge of each seam allowance with pinking shears. This technique is one of the easiest, but does not keep the fabric from raveling.

Stitched and pinked: Each seam edge is stitched approximately one-quarter inch from the edge and then the fabric is cut close to this stitching. This will minimize, but not eliminate raveling.

Zigzagged: Each seam is stitched with a short medium width zigzag stitch approximately one quarter inch from the edge and then the fabric is trimmed close to the zigzag stitching. This is an easy finish to your sewing seams and will keep raveling to a minimum.

Bias bound: Double-edge bias tape is wrapped around each seam edge with the wider side of the tape underneath. Stitch close to the edge of the top fold catching the tape underneath. This is a tailored finish for unlined jackets.

Sewing seams with a net binding: Cut half-inch wide strips of nylon net or tulle the length of the seam to be finished. Fold in half slightly off-center lengthwise. Wrap net around seam allowance edge with the wider side of the net on the bottom. Stitch on top side catching both the top and bottom portions of the netting. This type of finish is used on delicate fabrics and barely shows when using the same color netting as the fabric.

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