Use matching all-purpose or regular serger thread.
Use a new universal size 80/12 needle to prevent snagging and skipped stitches.
Use long pins with large colored heads to prevent the pins from being lost in the bulky fabric; pin sparingly.
Seaming
A flat, stable unstretched seam is ideal for sewing sweater knit. A 4- or 3-thread serged seam is the most desirable.
For loose-knit sweater fabric, first straight stitch the seam and then serge-finish the seams together with a 3-thread stitch (4).
For very bulky sweater knits, serge-finish the raw edges, then seam with a narrow to medium zigzag stitch (5).
Adjust the serger to a very wide, medium to long stitch to avoid stretched seams. For bulkier fabrics, use a longer stitch. Reduce the presser-foot pressure to minimize stretching and don't stretch the fabric as you serge.
Adjust the differential feed to a plus setting to avoid wavy seams. This setting controls the stretch by easing the fabric into the machine.
To construct sweaters with knit-on ribbing, serge off a thread chain and begin serging at one lower edge, matching the edges exactly. Serge to the cuff edge, stretching the cuff ribbing taut to help match the edges exactly (6). With a loop turner or tapestry needle, thread the serged chains into the loops of the seam to secure.
When applying ribbing, serge with the ribbing on top of the knit fabric. When setting in sleeves, serge with the garment on top so the under layers are eased into the top layer.
Minimize bulk at seam intersections by having opposing seam allowances go in opposite directions.
