How to Sew a Plain Seam

Hey, you!

In cooking, there are the mother sauces; and in sewing, the plain seam is the “mother” of all machine stitches.

That is, it is the foundation on which all other sewing skills are built.

In this article, you’re going to learn everything you need to know to sew those insanely gorgeous garments you’ve been dreaming of!

You will learn…

  • the anatomy of a seam; and
  • how to sew a plain seam

So if you’re ready, then let’s start with a few rules…

NOTE: If you’re ready to begin this journey and would like to buy my recommended tools and supplies, please click HERE!

The Rules of Sewing a Seam

Rule #1: If you want pretty seams (and you do!), slow down! You don’t have to sew at a snail’s pace, but you shouldn’t go at it a like you are an arctic hare!

Rule #2: Position yourself directly in front of the sewing machine needle. This is where you need to be to sew an accurate seam allowance with as little strain on your body as possible. Click HERE to learn about the ergonomics of sewing!

Rule #3: At the start of each stitching line, gently but firmly, hold both the bobbin and needle threads behind the presser. This will avoid gnarly, tangled up threads on the underside!

Rule #4: Please Do. Not. Watch. The. Needle! I don’t want you getting dizzy and falling off your chair. Because that would be unfortunate. Plus, it might just make you stitch an ugly, winding stitching line. And that is definitely not what we are striving for!

Instead, keep your eyes on the raw edge at the right as it grazes past the seam allowance markings on the needle plate.

Rule #5: Be safe, please! Keep your fingers at least 1” from the presser foot at all times!

Okay. Now that you know the rules, let’s learn…

The Anatomy of a Seam

A sewing machine stitch (also known as a lockstitch) is a simple thing. It is the result of the needle thread reaching down into the bobbin case looping around the bobbin thread, drawing the bobbin thread up so that they both interlock midway between two layers of fabric. Click HERE to see this in action!

Beautiful. Simple. Process.

Once a seam is sewn, this is its anatomy…

anatomy of a seam: stitching line, seam allowance, and raw edge

As you can see, there are three parts to a seam:

  1. the stitching or seam line;
  2. the seam allowance; and
  3. the raw edges.

Alright! Now that you know the anatomy of a seam, let’s learn…

Three Types of Straight Stitches

There are essentially three types of straight stitches:

  1. Standard, general straight stitch: Stitch length of 2.0 to 3.0mm.
  2. Reinforcement straight stitch: Stitch length of 1.5mm. Used on areas of high stress such as the pivot area around corners, V-necks, armholes, crotches, etc.
  3. Basting stitch: Stitch length of 4.0 to 5.0mm. Used for basting and gathering.

Okay. Let’s get busy learning…

How to Sew a Plain Seam

Sewing a plain seam is literally child’s play!

But first, you should keep in mind the following:

The average stitch length is…

  • 2.5 to 3.0mm for medium-weight fabrics;
  • 2.0mm for lightweight or delicate fabrics; and
  • 3.5 to 5.0mm for topstitching, basting, and gathering.

The seam allowance (SA) for commercial garment patterns is usually 5/8 inch.

The SA guide on your sewing machine needle plate is in ⅛ inch increments. But the seam guide on your needle plate is only accurate when the needle is in the CENTER position.

Alright. Now that you’re in the know, here’s how you sew a plain seam, step by step. And once you know how, each step will flow effortlessly into the next…

seam allowance guide on throat plate and masking tape

  1. Sit so that your body is positioned directly in front of your sewing machine needle. Click HERE to learn the ergonomics of sewing!
  2. If your sewing machine has a speed control feature, set it to a moderate speed. This way even when you press the foot pedal all the way, you will still only be able to sew at a sensible speed.
  3. Locate the appropriate seam allowance on the needle plate. If you need more guidance as you sew than the short line provides, take a piece of masking tape or washi tape and mark your seam allowance on your needle plate (see image above).
  4. Align the raw edges of your fabric with right sides together (RST). Generally, you want to place the bulk of your fabric to the LEFT.
  5. Now, position your fabric under your presser foot and align the raw edges at the right with the desired SA on the needle plate.

Also, align the top of the seam so it is positioned ¼ inch in from the top raw edge. This way you will avoid your fabric getting sucked into the hole on your needle plate when you begin to sew! Ugh!

needle properly positioned at start of seam

  1. Lower your needle either by pressing the needle position button or turning your hand wheel towards you.
  2. Lower your presser foot.
  3. Gently but firmly, hold both the bobbin and needle threads behind the presser.
  4. Still holding the threads, press the foot pedal to sew your first few stitches and secure the start of the stitching line; and then release the threads.
  5. Now continue stitching forward from the start to the end of the stitching line.

Again, as you sew, remember this: The needle isn’t moving, but your fabric is. So keep your eyes on the raw edge of the fabric to ensure an accurate SA from the start to the end of a stitching line!

  1. When you near the end of the stitching line, about ¼ inch away, prepare to secure it.
  2. Next, press your needle position button or turn the hand wheel towards you to raise the needle to its highest position and complete the last stitch.
  3. Raise your presser foot; pull your fabric towards the BACK of your sewing machine; and use your machine’s thread cutter to cut the threads.

And if there is some resistance as you try to remove your fabric from the machine at the end of a stitching line, just turn the hand wheel slightly towards you to complete the stitch and release the fabric.

Okay! How easy was that?!

Sew easy tip: The width of a standard measuring tape is exactly 5/8 inch, which is a very handy thing to know when you need to check the accuracy of your seam allowances.

using measuring tape to verify 5/8 inch seam allowance

The End

You now know how super easy it is to sew a plain seam.

And you also know that looking at the raw edges of your fabric –rather than the needle– is how you maintain an accurate SA from the start to the end of a stitching line.

Now that you can sew a plain seam, you’re ready to build your skills from there and learn several ways to secure the start and the end of a stitching line.

And remember…

Life is the ultimate red carpet event. Dress for it!

RELATED: Click HERE to learn all you need to know about stitch type, stitch length and stitch width!

RELATED: Click HERE to practice using your sewing machine!

RELATED: Click HERE to learn the basic sewing skills you need to sew insanely gorgeous clothing!

RELATED: Click HERE if you’re ready to begin this journey and would like to buy my recommended tools and supplies!

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