early on in my quilting life a teacher taught us this method
for 1/4" accuracy.--cut 3 fabric strips that are 1 1/2" by
4 1/2. sew these together lengthwise. gently press. they
should measure 3 1/2" across. if less than that,your seam is
too big--if more than that, your seam is too small. Adjust your seam (by sewing more strips) whichever way you need to, measure again. do it for each machine you use if swapping back & forth to finish a project. what foot you use, thread, does not matter as long as that strip is 3 1/2" wide. this
shows the seam in the fabric better than rulers, etc.