Assembling a flat knitted sweater or cardigan

I have started and never finished this cardigan. That is right, I didn't just forget to finish the series, I actually never finished the damn project I was working on along with this tutorial. And here is the most absurd part, this is not the first time, and it will probably not be the last, that this happens. This happens every single time that I knit a project that involves a lot of sewing. The second project that I ever knitted was a blanket made of squares I started in 2014. You read it right: 2014! I have knitted all the squares, assembled most of them and even used the mini blanket I obtained in my bed (I had to make the hard choice of covering my feet or my shoulder, yes, for real, I'm this ridiculous), but I still haven't finished sewing the whole thing. I love the damn blanket and sincerely it is totally gorgeous, if I say so myself. But still not finished, because I'm lazy and undisciplined.

But, going back to the damn cardigan. I have been working on it lately, but I still haven't got the sleeves right. The "sample" sleeve that I knitted does not fit the rest of the cardigan yet. However, in order to check this out, I started thinking of how to assemble a cardigan (or sweater). And when I tried to find information on this subject, I was shocked by how difficult it is to find a good tutorial or even some simple instructions. Books and online pages and videos often describe the different stitches you can use to sew the different seams of a cardigan, but rarely describe the actual assembly. The best info I found, even better than in my favourite books, is this tutorial by Valerie Gross. And, because I know webpages do not always last forever, I'll give a brief overview of the instructions there contained.

Yarn and notions

Do not necessarily use the same yarn you used to knit the rest of the sweater. In the case of the aforementioned cardigan, this was bulky and thick-and-thin yarn and both these characteristics make this yarn inappropriate for sewing a seam. Use a yarn that is sturdy, smooth and relatively thin (never bulky or super-bulky). In addition, use a compatible colour (and only when possible fibre content). Embroidery yarn may be a good choice: it comes in lots of colours, which makes it easy to match, and is sturdy and slips easily through the stitches. Finally, do not use a very long strand of yarn, as continued friction from pulling it through the seam will cause the yarn to fray and break. Use at the most 60cm/24in of thread.

Use a darning needle, in order to avoid splitting stitches: whatever seaming stitch you use, you always want your needle to go in between the knitted stitches.

Other notions you will need: pins (or any other notions that serve to attach the pieces together before beginning sewing; some people prefer clips), any notions you may need for blocking before seaming (a blocking board and T-pins or whatever your favourite method for blocking requires).

Order of assembly

1. Before you start anything: consider using an appropriate selvage stitch on every side edge of your knitting. A one stitch garter stitch selvage is a good option and the one I used in that cardigan.
2. Always block the pieces before starting the assembly. Stretch the different pieces so that they match, i.e. make sure that, for example, you stretch the different side seams to the same lengths and so on. I know this can be tricky. If necessary, reblock (or even reknit) until you get it right.
3. Start with seaming the shoulders. First, pin them in place, then sew.
4. If assembling a cardigan, you can now pick up stitches for the button bands and the neckline and knit them. Although most people prefer to assemble the whole thing before this step, the advantage of doing it now, is that you avoid the extra weight and bulk of the sleeves, while knitting. Alternatively, you can sew a zipper.
5. Now join the sleeves. Fold the sleeve in half lengthwise and mark the centre top with a pin and join it with the top of the body. Pin with the right side of the sleeve cap to the right side of armhole. The first pin should be inserted with the centre top at the shoulder seam, then pin to the cast off edges at the beginning of armhole shaping, easing the rest of the cap in so it is even on both the front and back of the armhole. Pin the whole sleeve top to the body before sewing the seam.
6. Finally, finish by sewing the sides of the body and the sleeves' seams.

Best stitches

Each seam you sew, namely the shoulders, the sleeves and the side seams, require a different stitch, because you are sewing different edges together. Here is a list of the best sewing stitches to do so, although there are other alternatives which may be appropriate for special projects.

• For the shoulders or any two bound-off edges, use an invisible horizontal seam stitch, also known as grafting. It essentially replicates the Kitchener stitch, but it is worked in two bound-off edges instead of live stitches. This is worked on the right side. Note, however, this is only a good option when using the exact same yarn, because the yarn used for seaming will be perfectly visible. If using a different yarn, like embroidery yarn, the backstitch seam stitch is a good option (read below).
• For joining the sleeves to the body, use a backstitch seam stitch. This is one of the best and sturdier stitches to join two different edges together. It’s worked on the wrong side.
• For the side seams, including the sleeve sides, use the mattress stitch, which is the best option when joining two identical vertical edges. It’s worked on the right side.
• Zippers should be sewn in by hand rather than by machine. Obviously, you'll use a normal needle, not a blunt-tipped one for this. Baste the zipper tape into place along one side, then whipstitch the tape on the wrong side. Turn the piece to the right side, and backstitch along the zipper teeth.