Adding sequin trim to an item you're sewing can add sparkle and make it look professional. Sequin trims are common on Halloween costumes, dance costumes, figure skating dresses and beauty pageant dresses. Because the sequins are difficult to work with, many people hand sew the trim, but it's possible, and sometimes preferable, to machine-sew sequin trim. Machine stitching sequin trim attaches it more securely, which is very important for clothing that will be used heavily.
Install a brand new heavy-duty sewing machine needle into your sewing machine. Put a drop or two of sewing machine oil on a cotton swab, and grease the point of the needle with the oil. The sewing machine oil will help the needle to puncture sequins when they get in the way. Keep your extra heavy duty needles close by in case you break your needle while you're sewing.
Wind your bobbin with all-purpose thread that matches your main fabric. Thread your machine with invisible thread or monofilament quilting thread. The invisible thread will not detract from the sequins, but it's best to use all-purpose thread underneath for stability.
Determine which direction you want your sequins to run. If you run your finger along the trim in both directions you'll find that your finger runs smoothly over the sequins in one direction and bumps up against every sequin in the other direction. You want your presser foot to leave as little damage behind it as possible, so figure out which way you want to sew the sequin trim on, and lay it out accordingly.
Use straight pins to pin the sequin trim to the garment. Leave a small tail of trim extending beyond the edge where you'll begin sewing.
Adjust your machine for a long zigzag stitch. Also, adjust the machine to run on its slowest speed. Run one zigzag seam down the middle of the trim if the trim is less than 12 mm (1/2 inch) wide. If the trim is wider than 12 mm (1/2 inch), secure the trim to the fabric using two seams, one on each side of the trim. Do not stretch the trim out as you go because the fabric underneath will pucker.
Stop sewing when you get one inch from the end of the seam. If you are adding trim to a circular piece such as the hem of a skirt, overlap the two ends of the sequins and secure them by sewing back and forth over the two layers. If you are adding trim to a straight piece that will not overlap the beginning of the seam, fold the end of the trim under so you don't leave a raw edge. Continue to the end of the seam and backstitch to secure the trim.
If you notice that your needle is continually catching on the sequins, rub more sewing machine oil on the needle or replace the needle itself with a brand new one. Adjust the sewing machine's tension if you see the bobbin thread poking up through the fabric.