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Welcome back to Lesson #5 of the How to Machine Sew series for beginner sewers! I asked on Facebook if you’d prefer another week of sewing lessons or some beach-related tutorials, and I got a unanimous “BEACH!!” Except I didn’t have my pictures all ready for the beach ones, so alas, those will have to wait til next week. This week I want to talk a little about something very important: seam allowance.
Seam allowance is the distance between the fabric edge and the stitching. This distance needs to be regular for even sewing and usually you need to follow strict guides when following a pattern or tutorial, or else your project could come out the wrong size or the parts could not fit together properly. Let me show you how to get perfect seam allowance.
Let’s get some woven fabric scraps (in this case, from one of my pillow beds) to practice on. Fold the fabric in half, iron it, and cut out some shapes so that you get two of each. I suggest at least one rectangle, one circle and one wavy shape.
First let’s talk about how to pin. When I started sewing, I placed my pins parallel to the fabric edges, as you can see (sort of) in the top picture above. Years later I realized that I found it much more comfortable to place pins more or less perpendicular to the edges with the pin head facing towards the right, beyond the fabric edge, as you can see in the bottom picture. I find that the fabric gets buckled less that way and it is also easier to sew right up to the pin (or even over it) and, being right-handed, it’s easier this way for me to pull out the pins as I sew. Experiment with what feels easiest for you and just stick with it.
Pin together the two layers of the shapes you cut out, wrong sides together.
Now let’s take a look at the needle plate on your sewing machine. You will see some lines and numbers on it, which are the seam allowance guides. Yours could look different from mine, so get to know how your guides are set up. My machine has the most standard imperial and metric seam allowances marked out. Metric seam allowances are generally broken up into 1/2 centimeters, so 10, 15, 20, 25 mm (etc.). The most common imperial seam allowances I see are 3/8″ and 5/8″, but you can get other fractions of the inch, too. I prefer metric, which I find a whole lot more simple, so I’m happy that my machine’s metric guides are closer to the presser foot. I also love that there are some guide lines on the transparent cover to my bobbin because I can sometimes align my fabric better with that and it also has some very small seam allowance guide lines that don’t fit on the other guides.
When sewing with seam allowances you line the edge of your fabric up with the seam allowance guides on your needle plate. The picture above shows how to position the fabric for 10 mm and 20 mm seam allowances.
While sewing, keep an eye on the guide line that you are using. Guide the fabric as necessary so that the edge is always along that line. If your fabric edge is straight, you can probably just let the feed dogs pull the fabric through. In the picture above, I am using a 10 mm seam allowance. You can see that I’ve sewn right up to a pin. I generally remove the pin when it gets right in front of the presser foot, but at times I do sew right over it. Just keep in mind that you can bend your needle this way if you hit the pin the wrong way.
Most sewing machines come with a useful little accessory, a fabric guide that you can screw onto either the presser foot or the needle plate. This can be really convenient if you are sewing a lot of fabric (like floor-length curtains) or curves because the guide physically stops the fabric from going beyond its edge, which you can set to whatever seam allowance you need. Another trick, which I like to use if I have to use a seam allowance that isn’t very visible on my guide lines, is to stick a strip of masking tape onto the needle plate at the right seam allowance. This way you can also make the line extend forward as far as you’d like, which might make it easier for you to line up the fabric correctly. Just make sure to remove the tape when you’re done sewing so that it won’t leave sticky residue.
Let’s say you’re sewing a shape with corners. You need to make sure that you get the same seam allowance on both sides of the corner. When you get near the edge of the fabric, stop sewing with the needle down, lift the presser foot, and turn your fabric. If the second edge falls along the right guide line, lower the presser foot and continue sewing. If the edge falls along a higher number (meaning a larger seam allowance), turn the fabric back to how it was before and sew another couple of stitches, then check again. If the edge falls along a lower number (meaning a smaller seam allowance), turn the fabric back to how it was before and backstitch a couple of stitches before checking it again. On the example above, you can see that I have sewn a perfect corner with a 10 mm seam allowance on both sides. This might sound like a pain in the butt to you, but it will make for more well-sewn work. And after a while you will develop an eye for the distance.
Things get a little harder when sewing curves because you can’t just let the feed dogs pull the fabric straight under the needle, or else you’ll end up sewing right off the edge if sewing a convex curve, such as a circle…
…or you’ll sew too far inside the fabric if sewing a concave curve, such as the “valley” between two convex curves. Whenever you sew along an edge that isn’t perfectly straight, you need to pay very close attention to the seam allowance guide right next to the needle (not a guide in another place on the needle plate) and constantly guide the fabric as you sew slowly so that the seam allowance is always the same. This is a case when it might be convenient to use a sewing guide accessory or stick on a little tab of masking tape, as I mentioned above.
When sewing very small seam allowances, I like to change the needle position. Not all machines have this function and there are different ways to do it on different machines, so consult your instruction manual. In the picture above, you can see how much my needle can be moved to the left and right of the default center position.
So how does changing the position help? If you need to sew with a small seam allowance you probably won’t have a guide line to align the fabric as you feed it through the machine. Another problem you might have is that the fabric edge could get caught under the feed dogs if you position it too far in under the foot. So what I like to do is align the fabric with the right edge of the presser foot and move the needle all the way over to the right. On my machine that creates a perfect 4 mm seam allowance. If you need a 5 mm seam allowance, move the needle over just slightly to the left, if your machine allows you to. I love using this trick when topstitching (which I’ll cover in another lesson).
Now practice sewing with different seam allowances on both straight and curved pieces. Don’t forget to practice corners and both convex and concave curves! Try different seam allowances and get used to keeping an eye on the guide lines on the needle plate. Then on Friday I’ll have another practice tutorial using seam allowances to create something useful for your home or that you can give away as a gift! Stay tuned! (edit: here’s the practice tutorial: felt coasters with simple reverse appliqué!)
Did you enjoy this lesson on sewing with seam allowance? Take a look at the other lessons in this beginner’s sewing course!
