Originally Posted by smitty
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. ...
Here's another way to test using these three strips: I use a lighter strip for the center, then press the seams away from the center strip. If the center strip measures exactly one inch after pressing, your seam allowance is perfect. If not, adjust the seam allowance by one thread-width at a time until it measures exactly one inch.