Sewing a T-Shirt Part 2: Sewing the Seams

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Sewing a t-shirt with knit fabric is a challenge, but if you followed Part 1 of this tutorial, you’re already on your way! In the first part of this series, we learned how to choose a pattern, pick out fabric, determine your size, and cut out your fabric. If you need help with any of those steps, be sure to go back to Part 1 before diving in here!

In Part 2, we are going to learn how to sew your fabric together at the major seams. This includes the shoulders, sleeves, and sides. After completing this step, your knit t-shirt will start looking like an actual shirt!

If you have your fabric pieces cut out, you’re ready to start this part of the tutorial. Let’s begin!

For the most part, you can follow the instructions that came with your pattern. However, this tutorial walks you through everything in much greater detail, explaining concepts that might be confusing when reading a pattern.

Still need fabric? This is a great place to buy knit fabric!

Supplies & Tools

For this part of the tutorial, you will need the following:

• A sewing machine* or serger (highly recommended).
• Ball point needle (if using a regular machine).
• Pins or quilting clips.
• Thread snipping scissors.
• Matching thread.
• An iron & ironing board.

* I understand that sergers are expensive and not everyone has access to one. You can sew a knit t-shirt with a regular sewing machine as long as it’s capable of doing a zig-zag stitch. However, the end result won’t look as polished and the seams will be a little less sturdy than those you would get from a serger.

If using a regular sewing machine, I recommend the following:

• Buy a walking foot for your machine. This type of foot lifts up and down as you sew, which helps pull the fabric along neatly. It’s super useful for knit fabric.
• You could try wooly nylon thread instead of regular sewing thread. Wooly nylon is stretchy, where as cotton sewing thread is not. Keep in mind wooly nylon is a little more difficult to work with.
• Wonder tape can help hold your seams in place if you’re having trouble getting things to look neat when sewing on a regular machine. Wonder tape is water soluble, double-sided tape that you can use to secure two pieces of fabric together. I still recommend pinning if using this tape.

Step 1: Determining the Right Side of the Fabric

Before pinning, we need to figure out what side of the fabric is the “right side” and “wrong side.” The right side will be on the outside of your shirt. It’s sometimes a little challenging to find the right side of a knit fabric.

With knit fabrics, the right side has tiny V-shaped stitches. You should see thin vertical lines running up the fabric on the right side. The wrong side will look more like tiny, wavy, horizontal lines — kind of like little nubs or dots.

In almost all cases, you will need to pin your fabrics right-sides-together. In sewing, you might see this abbreviated to RST. When you sew with your right sides together, the seams will be on the wrong side and will be hidden inside the garment.

RST = Right Sides Together

Step 2: Pinning & Sewing the Shoulder Seams

Almost all shirt sewing patterns will have you start by sewing the shoulder seams together. Unless your pattern has a really unique construction, you will start with this step.

Lining up the Fabric

I like to lay the shirt back on the table with the right side facing me. Then I place the shirt front right side down on top of the shirt back. These pieces will now be RST.

Make sure you line up the shoulder seams so the raw edges of the front and back are aligned. You don’t need to worry as much about the rest of the fabric being flat. As long as the shoulders are lined up you can start pinning.

Pinning

I like to use quilting clips to hold my fabric together because they have a very firm grip. It’s also nice not poking yourself with pins accidentally!

Use as many clips or pins as you need. Knit fabric can be tricky to sew because of how stretchy it is. Depending on the kind you’re using, it may also want to roll or slide around. Using more pins can help.

If your pattern has notches or other markings, make sure to line these up when pinning. This helps you align your garment properly.

Seam Allowance

After you’re done pinning, refer to your pattern instructions to see what the seam allowance is. This will affect how your shirt fits, so make sure you’re following what the pattern says.

Before sewing, it helps to understand directional sewing. This is the concept of sewing matching seams (e.g. two shoulder seams) in mirroring directions. For example, you would sew both shoulder seams starting at the neck opening and ending at the sleeve opening. Or vice-versa. Fabric slightly pulls along the direction you are sewing. On long seams, the direction of sewing can affect how the seams lay. Directional sewing ensures that your garment is aligned perfectly.

Sewing

I recommend practicing on a piece of scrap fabric before sewing your actual garment. Use a piece of leftover fabric from cutting out your pieces. This will help you see if your tension and stitch length is correct. Refer to your sewing machine manual for troubleshooting.

Finally, sew your shoulder seams, removing the pins/clips as you come to them. If using a regular machine, make sure it’s set to a zig zag stitch. This will stretch with your fabric, whereas a straight stitch may snap when the fabric is stretched.

Pressing

After sewing your seams, be sure to press them with an iron. Be sure to lay out the seam as instructed by your pattern. It may tell you to press it towards the front or back of the garment. To press your seams, you will place the iron flat on the seam and lift it up. Repeat until the seam is in place.

You don’t want to iron your seams, which is when you move the iron around in a circular motion. This doesn’t matter as much on short seams, but it can distort how your garment lays when you iron longer seams.

Step 3: Sewing the Sleeves and Sides

Here is where t-shirt sewing patterns deviate from one another. I recommend following whatever order your pattern says to do. However, most t-shirts are so basic that you could use either method for assembly.

• Some patterns will have you sew the sleeve into the shoulder as soon as you have sewn the shoulder seam. You will pin the sleeve to the shoulder, then sew from one side to the other. After doing this, the side seam will be sewn in one continuous line from the end of the sleeve down to the bottom of the shirt.
• Other patterns will tell you to sew the side seam of the shirt and the side seam of the sleeve separately. Once sewn, you will insert the sleeve into the shirt and sew around the opening to secure the sleeve in place.

Sewing the Sleeve in First

If sewing the sleeve onto the shoulder, you will line up any notches or pattern markings and pin the sleeve to the shoulder opening RST. It can be tricky to visualize this, so I’ll be posting a video to show how this is done. I like to start pinning at the top of the shoulder and work down to the underarm on both sides.

You can now sew the sleeve in place. Be sure to press it after sewing. Your pattern will tell you which direction to press.

Next, lay your shirt RST and pin along the entire edge from the end of the sleeve to the bottom of the shirt. Make sure to line up any pattern markings and align the underarm seams together.

Finally, sew along the entire edge in one continuous seam as shown below. Finish by pressing your seams.

Sewing Sleeves and Sides Separately

If sewing the side seam and sleeve seam separately, you will pin the shirt body RST along the side. Next, you will fold the sleeve in half RST and pin along the underarm seam. Sew both of these seams separately. Press the seams.

After sewing and pressing both seams, leave the shirt RST. Then turn the sleeve inside out so that the right side is facing you. Insert it into the sleeve hole on the shirt. The right side of the sleeve should now be facing the right side of the shirt body.

Starting at the underarm seam, pin all the way around the opening. You can now sew the sleeve in place. Finish by pressing the seam.

Next Up: Attaching the Neck Band

After sewing the shoulders, sleeves, and sides, your shirt should now start looking like an actual garment! The next step is to attach the neck band. Read Part 3 to learn everything you need to know!

I hope you’re enjoying this blog series and I would LOVE to see how your shirt is coming along. You can tag me @craftingwithclementine on any social media platform (Tik Tok, Insta, YouTube, Threads, and Pinterest) or use #CraftingWithClementine.