This is by no means an exhaustive list of seam finishes, but rather what I consider to be some of the most commonly used. These are the finishes I recommend for my patterns, and therefore what I wanted to have documented in one place.
In each of these examples, I have finished the seam allowance as one BUT you may choose to press the seam apart, and finish each side of the seam allowance separately. Pressing to one side will be bulkier and will make it harder to alter later (as in a garment), but it’s also faster. Keep these things in mind and decide on a case-by-case basis. Also, follow the directions of any pattern you are using–if it tells you to press the seam apart or press to one side, you’ll know to finish each side separately or as one.
FRENCH SEAMS
I love french seams. It doubles the amount of stitching for each seam, but the finish is clean and extremely professional-looking. I can tell that a RTW garment is high-quality when it’s sporting french seams. French seams are great for delicate fabrics. Alternatively, they are not ideal for bulky fabrics. They are best for straight seams and not ideal for curves (like set-in sleeves).
In this example, I’m using a seam allowance of 1/2″, but if you are using a different seam allowance, no worries–you simply want the math to add up at the end.
1) Place your fabric wrong sides together. If you’re sewing with a printed fabric, this means that the non-printed sides are placed together. Your sewing senses will detest you for this, but carry on. Everything will end up like it should. Sew a 1/4″ seam allowance (if you’re using a 5/8″ total seam allowance, you may wish to sew this step at 3/8″).
2) Trim the seam allowance down to 1/8″.
3) Open up the fabric and press, making sure that the seam is pressed apart fully.
4) Fold the fabric right sides together, enclosing the first seam. Sew at 1/4″ seam allowance (or whatever you need to hit the final needed seam allowance. If you need 5/8″ and sewed the first seam at 1/4″ [which is 2/8″], then you need sew this one at 3/8″).
Now press to one side and admire the beautifully enclosed raw edges! Optionally (and not pictured), you can topstitch the french seam down to one side, which would be a design element as well as extra security.
SERGER
A serger is also known as an overlocker. It is “overlocking” the edges of the fabric using 3-4 different cones of thread. It has a knife that, when engaged, trims the raw edges of the fabric as you sew. If I’m using a fabric that is prone to unraveling, I will sometimes run each edge through the serger to prevent fraying as I handle the pieces. A serger is also great for sewing knits, because the nature of the serger’s stitch is very stretchy.
A serger’s stitch is also time-consuming to remove, so it’s best to serge each side of the seam allowance separately if you think at all that you might need to alter the seam later. If I’m sure I won’t, and if the bulk doesn’t matter, then I serge the entire seam allowance together and press it to one side (I almost aways do this on the skirt portion of my daughter’s extra-roomy dresses).
Another thing you can accomplish with a serger is faux flat-felled seams. Serge the entire seam allowance together, press to one side, and topstitch it down. I do this in pants and jeans.
OVERLOCK STITCH – SEWING MACHINE
This one will depend on the machine. Mine came with an overlock foot and sews an overlock stitch. This is essentially what a serger does–except on the sewing machine! It does require a special foot and setting, so take a look at your instruction manual to see what your machine is capable of.
ZIGZAG STITCH – SEWING MACHINE
This one is quite easy–simply use your sewing machine’s zigzag stitch inside of the seam allowance. You can stitch right next to edge of the fabric, or you can stitch further into the seam allowance and then trim (in the below example, I would trim 1/8″ off). Alternatively, if you have an overlock foot for your machine (see previous section), you can zigzag right at the edge!
PINKING SHEARS
Pinking shears are simply fabric scissors that cut a zigzag shape. The shape in and of itself prevents unraveling. Trim and done! If you’re using a fabric that unravels easily, you may wish to add a line of straight stitching between the seam and the pinked edges, just for extra insurance.
BOUND and HONG KONG SEAMS
There are some different ways to do this, but this I’ll show you how I do it. You’ll need 1/4″ double fold bias tape. You can buy it from the fabric store in packages, or you can make your own. I almost aways choose to make my own because it’s cheaper and I can match my project. And the quality is better! If you choose to make your own, use a lightweight fabric, no heavier than quilting cotton.
OPTION #1
The first option is pretty straightforward. You wrap the bias tape around the unfinished edge…
And sew it down, really close to the edge. Your stitching will be visible on both sides, so I recommend using a coordinating thread, not contrasting like I am for the purpose of this tutorial. 
OPTION #2
This is how you machine bind quilts. If I’m binding a curve or a hard-to-get-to seam (like the inside of a bag), I use this method. It’s more work, but easier to make sure it’s secure.
Open up the bias tape and align to the edge of your seam. Pin in place.
Stitch at 1/4″ seam allowance, just shy of the fold line of your bias tape. Trim bias tape seam allowance to 1/8″.
Wrap the bias tape around the edge to the bottom and pin in place, making sure that the bottom part you wrapped around reaches just a teeny bit further than the part on top. Now you want to “stitch in the ditch,” (see below), catching the very edge of the bias tape underneath.
The top photo is the top, where you are stitching in the ditch, and the bottom photo is underneath, where you are catching the very edge of the bias tape.
My example above is a bit messy because I had a wriggling 15-month-old in my lap trying to “help” me…bless her. 😀
Now you may press to one side and admire your beautiful seam!
Hong Kong Binding is simply binding each side of the seam allowance with the above method, except you unfold the portion that wraps underneath and trim. It takes a lot of time and a lot of work and you tend to see it in unlined jackets or coats, on the straight seams only. In RTW, you would only really see this in the most couture of garments. It is beautiful and adds a lasting, couture finish.
Those are the finishes I tend to recommend for my patterns. I almost always use my serger, but do bind seams when I’m feeling particularly fancy. 🙂 Which one(s) do you tend to use?
