I know it probably seems like a simple thing but i’d like to share with you a few tips on sewing buttons onto your knitted garment.
First of all don’t use the project yarn, it’s best to use sewing thread, just about any thread fine enough for machine sewing will work. Some people will insist on polyester because it’s strongest but cotton-wrapped polyester, cotton, or even silk is probably okay. You can use buttonhole thread or upholstery thread if you’ve got it lying around, but I like to buy thread to match if I can.
Once you have the buttons and thread ready, what I like to do first is find the position for the button by closing the garment, lining up button band and buttonhole band just where I want them. Then, I mark the spot with my needle and thread by making a first stitch on the far side of the garment through the buttonhole.
I like to have my thread doubled and knotted at the far end. This makes sewing on the button faster (twice as strong with fewer passes!) and gives me an easy way to secure the first stitch, rather than having to make a knot. You instead attach the thread by looping the needle through the loop created by the doubled thread.
Slide the button into place.
Now for the sewing: Go through the back of the button band, then back up and through the button three or four times, not too tightly. Make sure to go around both "legs" of one knit stitch to help your button lie flat and avoid pulling too much on one strand of yarn; this can distend your stitch.
On the back of the button band, give your button a wide base to help it lie flat and to protect your knitted garment. If you just can't avoid tightening up, try putting a toothpick or crochet hook between button and garment, then slip it out before the next step. Bring the needle back through the garment to the space between the garment and button. Wrap the thread around the sewing, creating a shank. Now pull the needle back down through the shank and wrap it around the shank crosswise. I like to do this three or four times to assure security. Pull the thread to the back of the button band and tie a knot—again, I tend to wrap and knot a few times. Now you can snip the thread and you’re done!