Welcome to part 2 of our Seam Basics series! If you missed part 1 of the series on woven fabrics, you can check it out here. Today we’ll be covering all things Knit seams. Knit fabrics can be intimidating – but fear not – this sewing 101 will give you the tools and confidence you need to succeed!
First, you need the right tools
A walking foot attachment for a regular sewing machine eliminates any distortion the knit fabrics may experience while being sewn. It makes for a much cleaner seam, better seam performance, and an enjoyable experience!
Universal Ball Point Needles
Universal ball point needles are generic machine needles that can be used on most knits. Stretch or Jersey Knit needles may also be appropriate depending on what kind of knit fabric you’re working with.
Stretch needles have a longer scarf (better for knits with more than 5% Lycra Spandex).
What you need to know about knits
Knit Fabrics are made up of interlocking loops of fine yarns. The rounded point of a machine needle glides through the fibers rather than penetrating them, preserving fabric quality.
Knits can have mechanical stretch and/or Lycra Spandex generated stretch.
Mechanical stretch refers to the natural give that the interlocking loops experience when being pulled. The looser the loops have been knitted, the stretchier the fabric will be.
Lycra Spandex stretch refers to the incorporation of 1-20% Lycra Spandex fiber that has been added to the primary fiber contents. This gives any fabric stretch, and makes knits extra stretchy since they already have mechanical stretch by nature.
Zig Zag Stitch
This is a very basic stitch that joins knit fabric, and accounts for lengthwise (vertical) stretch. Simply trimming any excess fabric from the seam allowance will reduce bulk. This stitch is not ideal for tight, form fitting knit garments – because the fabric can pucker through the zig zags when heavily stretched on the crosswise (horizontal) grain.
Shallow Zig Zag Stitch
Also called “narrow zig zag” - this stitch resembles a straight stitch, while still accounting for some stretch. The fabric will not pucker through the seam stitch. This seam is great for knits that will not be stretched vertically, since it can be slightly limiting to lengthwise stretch. For the zig zag stitch examples, we used Kaufman Laguna Jersey Knit in Pink.
This straight stitch is made possible by switching your machines settings to “stretch”. It has the appearance and function of a straight stitch, but each stitch is actually made up of 3 lightning bolt style stitches. This accounts for stretch vertically and horizontally, making it a great stitch for knits. Two downsides to this stitch is that it takes a bit of extra time to sew, and it is almost impossible to remove if the seam without damaging the fabric, should the seam need to be undone for any reason. For this example, we used Riley Blake Jersey Knit in Hot Pink.
4-Thread Overedge Stitch
This seam is the most common for professionally made knit garments. This seam can be done on a 4 or 5-thread serger. Sergers have an adjustable “differential feed” function that beautifully sew knits or any other fabrics that have a tendency to distort under pressure. For this example, we used Fabric Merchants Stretch Cotton Jersey Knit in Bright Coral.