I use a 3/16 of an inch and find that makes a good scant 1/4. That brings you in a couple of threads from the 1/4 mark, my needle doesn't move left or right, my bigger problem is the hole that is to big for the needle to go into and the company doesn't make a smaller one. I am working on a quilt that has 1 5/8 in squares and the pieces need to be sewn that scant 1/4 of an inch. I would think that by now the quilting industry would make that phrase into a number measurement. I don't know metric but I am going to look into that--jna