There are other ways to hem a T-shirt or knit fabric without using a twin needle. (To learn how to hem a T-shirt with a twin needle, read here.)
You’ll need a “stretch, ballpoint” needle in your machine. This special needle is designed for sewing on knits. The slightly rounded, or ballpoint needle tip eliminates fabric needle punctures and skipped stitches.
For best results, test hemstitching method of choice on a scrap of the T-shirt you are working with before sewing on your project. If the presser foot pushes fabric ahead, you’ll need to reduce the presser-foot pressure (refer to machine manual for instructions). Practice stitching on scraps until desired hem finish is flat and smooth.
For each of the knit hemstitching techniques, prepare T-shirt knit for hemming by turning under the hem allowance, pressing and pinning it in place. All hems are stitched with the outside of the T-shirt facing up. Remove pins before needle reaches them.
Straight Stitch Hem
Set machine for a straight-stitch, 10-12 stitches per inch (2.5mm setting). Stitch on right side of T-shirt 1/4" from hem allowance edge, stretching fabric slightly as you sew. Add a second row of stitching, again stretching while sewing, 1/8" to 1/4" from first row. Steam hem, if needed, to eliminate ripples. Stretching the knit fabric as you sew will help to prevent popped stitches when garment is stretched.
Set machine for a 3.5 mm wide, 1.4 mm long zigzag-stitch. Zigzag stitch on right side of T-shirt 1/4" from hem allowance edge. Do not stretch fabric as this causes ripples. Allow fabric to feed under needle without stretching. The zigzag stitch has built-in stretch.
Multistep Zigzag Hem
Set machine for 3.5 mm wide, 1.4 mm long multi-step zigzag-stitch. Zigzag stitch on right side of T-shirt 1/4" from hem allowance edge. Do not stretch fabric. The multistep zigzag stitch has built-in stretch and is ideal for stitching knits and elastic. (Not all machines have multistep stitches. Refer to machine manual.)
Set machine for 2.5mm long stretch-stitch. (Triple stretch-stitch is shown.) Topstitch on right side of T-shirt 1/4" from hem allowance edge. Add a second row of stitching 1/8" to 1/4" from first row. Stretch stitches are ideal for sewing on knits as they build stretch into the stitching. (Not all machines have multistep stitches. Refer to machine manual.)