Hemming knit pants differs from hemming other types of pants because the fabric is stretchy, so an initial zigzag stitch is required to stabilize the fabric. Hem a pair of knit pants with instructions from a sewing craftsman in this free video on sewing.
Hi my name is Sam Lewis from madebysam.com and I'm here to talk about putting a hem in knit pants. The only difference between knit pants and any regular dress pants is the fabric itself which is stretchy and it also is much thicker than normal dress pants. So in a perfect world what you would love to be able to do is to put an edge on it with a serger. Failing that what you need to do is take your pants before you put the hem in them, you are going to want to put them in the machine and run a zig zag stitch to stabilize the material around the edge. Once you have done that go ahead and turn your material close to your stitching but not overlapping it. Once the edge of your fabric is prepared, turn it over to the inside like you would a normal hem and in this case we haven't premarked it but pull it to the line that you marked for your hem length and then you're going to want to pin it all the way around. We'll do it once to give you the idea but pin all the way around and you're also going to want to press the fabric so you have got as sharp a crease that you can get given that knit fabric doesn't really want to press well. You are going to go ahead and edge sew like you would any normal hem between 1/16 of an inch and 1/8 of an inch from the edge of the material. You want to be very careful when you are sewing with knit materials to keep your tension between the top and the bottom piece of fabric even, overlap your seam sewing, reverse for two or three stitches, lock your stitch and you're done. Turn it inside out and you have your hem.