Updated: Jul 21
I struggle with this post simply because I am more of a free spirited improv quilter and tend to work without a pattern so I don't always worry about a perfect seam. With that being said, I feel it is important to share with you why a consistent .25 inch seam is important when following a pattern.
A pieced block can have many seams and a quilt can have many blocks, sashing and borders. Lets just work up and example.
An extra 1/8 (0.125) inch per block multiplied by 10 blocks results in a 1.25 inch decrease in each row. This does not take into consideration sashing, cornerstones and borders. I have seen as much as 3-4 inches of difference in the actual measurement vs the intended measurement of the pattern. It all goes like a snowball downhill from here. If the borders are then cut to the pattern instructions there will be a significant differences in the measurements of the quilt at different points. Remember your quilters #1 love language is a square quilt.
There are multiple ways to check and maintain your .25 inch seam allowance. I take the thread out of my sewing machine, get a piece of paper to help me gauge by sewing on the paper. The first set of sewing was using the needle plate of my machine. As you can see it is slightly on the high side of .25"
The second set of sewing in measured by moving my needle down with the hand wheel onto a .25 inch mark on a ruler. As you can see it rests right on the .25 inch mark.
There are multiple ways to achieve an accurate .25 inch seam. I really like a good .25 inch foot, they aren't expensive and are easily found at most dealerships. There are some drawbacks to some of them. The .25 inch foot on my Juki is solid and will sometimes catch a stray thread causing my fabric to bunch behind the presser foot. I have also found that I cannot run my fabric exactly up against the foot because it creates a + .25 inch.
The simplest way is to place a ruler under your presser foot and slowly lower your needle by moving the hand wheel. I like to let the needle rest ever so slightly on the inside of the .25 inch mark instead of directly on it. Place a piece of blue painters tape or a magnetic stop on the outside of the ruler. Once you have done this sew a test piece and measure your seam for accuracy. If you feel it is on the greater side of .25 inch repeat the process.
I hope you find this helpful and not stressful. If all else fails try your hand at some wonky patterns or better yet improv. Happy quilting!