Originally Posted by Neesie

Since your needle can't be moved in tiny increments, try using a different foot. If you have a foot with a groove in it, like for satin stitch, give that a try. I accidentally found out one particular presser foot will give me a scant 1/4", by moving my 1/4" into its groove, just a bit past a true 1/4".

On my old machine, I would sometimes measure each presser foot, until I found one of the proper width, for whatever seam I wanted, then used the edge of that foot, as a guide.