A few of you have asked how I get my topstitching to look so perfect. First, it’s not always perfect (in RTW either!) but thank you for thinking so!
Almost always, I use a straight-stitch foot for topstitching. I like the sort of foot that has a slot where I can see straight up to the needle. I guide my fabric right along the inner edge of the right toe so that I’m stitching about 1/16″ away from the edge (if I want to stitch about 1/4″ away from the edge, I use the outer edge of the toe as my guide). Yes, this does take practice but having the proper foot really helps – you cannot do this with a zigzag foot!
There are also specialty feet available for my commercial machines that work very well if I am in a hurry or tired. This first set is unique to the commercial world. These are compensating feet in various widths. These are available with the spring toe on the right or on the left (mine are all right except for the first one).
Here you can see the right toe rides lower than the stationary left toe so the edge of the fabric butts up against it.
You can see here that the stitches on the left are a little longer (around 2.5) than the ones on the right. The thread I am using is heavier than what I’d normally choose for a silk crepe de chine so it looks better at a slightly longer length. Always run a couple of samples before you get started.
Next is a raising foot which is more similar to what is available for domestic machines. Raising feet also come in various widths, this particular one is a right 1/16 (these also come in left). A comparable domestic foot would be an edge foot or edge guide foot which typically comes in one width only but you can move the needle to topstitch further away.
Whichever type of foot you feel the most comfortable with, the key is to just do it and practice, practice, practice (a smooth, precision sewing machine is a huge help as well). Also notice that I like a shorter stitch length. To my eye, a long stitch length on a fine fabric looks cheap so I use a length of 2 to 2.5, depending on the fabric and the thickness of thread I am using. A longer length would be used on heavier fabrics.