The Wrong Needle

• Standard sewing machine needles have sharp points that push through the threads on the fabric. While this type of needle works well on woven fabrics, it can cause knit fabrics to snag. It can also make the sewing machine skip stitches, resulting in a weak seam. If you notice your fabric snagging or that the stitches are uneven when you use a regular needle, try using a ballpoint needle instead. Its tip is slightly rounded, so that it pushes between the threads of the fabric, not through them.
  
  

The Wrong Stitch

• A short running stitch on knit fabric will cause the stitches to pop when the fabric is stretched. To prevent popped stitches, you need to use a stitch that will stretch along with the knit fabric. A zigzag stitch has some elasticity to it and is ideal for use with knit fabrics. If you really dislike the zigzag stitch, you can use a slightly longer running stitch. Stretch the fabric gently as you sew the seam to make a stitch with some elasticity. If you have a serger or overlock machine, you can use that instead of a standard sewing machine to sew knits.
  
  

The Wrong Thread

• Cotton thread does not have the stretch that knit fabrics need. When sewing knits, try to use a polyester thread or a cotton thread wrapped in polyester. Nylon thread provides the most elasticity, particularly if used as the bobbin thread. Since nylon is very stretchy, it's best to wind the bobbin by hand to prevent it from stretching out as you wind it. If the fabric you're sewing is lightweight, use a thin thread. A medium weight thread will work for all other knits.
  
  

No Reinforcement

• Knit fabrics usually do not have the stiffness or body that woven fabrics have. The finished product may become misshapen quickly if you don't attach interfacing or another type of stabilizer to the back of the fabric. Non-woven, fusible interfacing provides body to delicate areas such as the hem, neckline or shoulder seams. A stabilizer can also make button or zipper closures stronger. A reinforced buttonhole is less likely to be pulled out of shape, for example.