If you're like me, it took me awhile to get the hang of using a scant 1/4" seam. Much of my
previous professional life in the shoe industry was using the metric system (centimeters vs. inches), so not having a true measurement of the "scant 1/4" was difficult for me to grasp at first since (spoiler alert!), I prefer the accuracy of the metric system much more than the Customary/Imperial system we use here in the States. But that is neither here nor there...
Back to the scant.
Initially, I just eyeballed it. I landed somewhere in-between 1/8" and 1/4" and called it good, but as I continued making quilts using a scant 1/4", I began to understand why it is necessary to really understand what this measurement is asking for. So what is a Scant 1/4"?
The true definition of a Scant 1/4" is one thread width short of exactly 1/4".
That's it. There you have it :)
When is it a good idea to use a Scant 1/4"?
Here are a few times to consider it (if your quilt pattern does not already suggest it):
When you're piecing a block that is complex with a lot of seams. The reality is that as you're sewing and pressing your block together, very small amounts of fabric are lost in your seams. When you press your seams, especially when pressing to one side, your fabric is essentially folding itself over the thread and you lose the amount of fabric that is wrapping itself back around that thread. This may not seem like much, but with lots of seams in one block, all these small amounts add up!
Below is an example of how quickly this small difference can add up:
Each of the below strip sets was sewn together using (4) 2 inch strips. Taking into account the seam allowances from sewing the strips together, the resulting length should be 6.5 inches (8 inches - 1.5 inches of seam allowance).
- As you can see above, the set on the left (green) used a true 1/4" seam. This strip set ending up being shorter than the 6.5 inches needed.
- The strip set on the right (blue) used TOO scant of a 1/4" seam resulting in a strip set that is longer than the 6.5 inches.
- The middle set (peach) used a scant 1/4" seam and ended up right on the nose with a 6.5 inch length.
When using thicker fabrics. The most obvious fabrics that come to mind when discussing thickness would be canvas, flannels and some woven fabrics that are often thicker than quilting cotton. But there is also a difference between fabric manufacturers in the thickness of some quilting cottons. For instance, Kona Cottons and Moda Bella Solids generally have a heavier weight/hand than AGF Pure Solids and therefore would be subject to lose more.
When using thicker thread. Generally a 50wt thread is used for piecing quilting cotton, but if you use 40wt thread, which is slightly thicker, you may need to consider the scant 1/4" seam regardless of fabric weight.
For my pattern Fourth and Inches, available in August 2023, I recommend using a scant 1/4" during the assembly process due to the strip piecing of many narrow strips to form the center of half of the quilt blocks. This particular block involves piecing nine strips together, so you can imagine if you lost a
fraction of your seam allowance every seam, say 1/32", that fraction would be multiplied eight times resulting in 1/4" difference in the length of your center strip vs. outer edge strips of your block.
The unfortunate part of the Scant 1/4" is that it truly is achieved by trial and error on your own machine as every machine set-up is different. BUT once you identify how you need to set up your machine to achieve your Scant 1/4", you'll be set and can confidently depend on that set-up (but it is always good to double check before beginning a new project!).
Tips for Finding your Scant 1/4"
Start with the presser foot that you use on your machine to sew a true 1/4" seam allowance, sew a test line and measure.
I know, I know, if you're an experienced quilter, sewing a 1/4" seam is something you do, day in and day out, but it is good to get a true idea of where you are at before you make adjustments.
Once you identify your true 1/4" seam allowance, you can adjust the following ways:
1. Move your needle slightly to the right.
In my case, my machine (a Bernina B350 SE) I only have to push the needle position button once and it is enough for the scant 1/4". Based on your machine, you may need to do some trial and error to find the best needle position adjustment.
2. If you sew on a straight stitch machine (without the ability to move the needle), you can adjust the placement of your fabric edge to just inside where you normally place it for a 1/4" seam. This may require more testing and I recommend using Washi tape or seam guide tape (I use this tape from Cluck Cluck Sew ) to mark your placement before testing so you can use that as a guide once you are ready to sew.
A few more helpful tips:
Use a seam edge guide on your presser foot.
This can be especially helpful for
consistency of the scant 1/4" as it helps to rest your fabric along the edge of the guide. My Bernina foot #57 is my go-to for scant 1/4" piecing but you can also find a magnetic seam guide to attach to your machine if you don't want to buy the whole foot.
Be sure your stitch plate accommodates for your new needle position before getting started. Straight stitch plates generally have one small hole vs. the wider oval on a stitch plate that is used for multiple stitch types.
And there you have it. A pretty simple process but an important one when you need it for your piecing.
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