Hemming sheer or delicate fabric can be frustrating. The first time I tried it, I ended up with a hem that was an inch shorter than I had planned. Even after the stiches were in, I was extremely unsatisfied with the wavy and uneven turn under. Since then, I have used a method which is more sewist-friendly and the results are a lot more pleasing.
Assuming the hemline is marked where desired, trace the imaginary line with a contrasting thread. This will serve as a general guide for you sewing. I like working with the garment while it’s hanging (instead of flat) so it is more obvious if my marking stitches are not transitioning gradually.
Once the hemline is marked with hand stitching, take it to the sewing machine and stitch (I usually use the longest stitch length) a quarter inch below that line. Starting at 1/8″ below the machine stitched line, cut off the excess fabric.
The machine stitching works great as a guide to turn up the raw edge. This is especially true in the case of designs where the raw edge happens to be wider than the skirt edge to be turned up upon (for example: A-line, circular, or semi-circular designs). When turning up the raw edge (wrong side to wrong side) I make the fold not on the stitching, but about 1/8″ above it. After the first turn up, fold up the folded edged where the machine stitching is. Use the tension of the machine stitching to help make that fold by pulling it taught. Pin the turned up edge in place.
The most difficult part has arrived; that is guiding the narrow folded fabric through the presser foot and feed dogs while stitching a straight, or uniform, line from the edge of the fabric edge. The best way to achieve great results with this last part is simply practice.
I hope you have a successful turnout of your sheer hems.