Let’s Talk Seam Allowance: Back to School Lesson

Most of us know that a 1/4-inch seam allowance is used in quiltmaking. But we also know that sewing an accurate 1/4-inch seam allowance is not always easy. If ever there was a block to quickly make you aware of your seam allowance, Frame by Frame fits the bill.

BTS12 blockassembly1 Lets Talk Seam Allowance: Back to School Lesson

Even though this is a simple block, there are six seams across the A/B section. That means six chances for inaccuracy to rear its ugly head. If you are off by just two threads in each seam, over six seams that adds up to 1/8 of an inch. If you are off by just three or four threads in each seam, over six seams that adds up to 1/4 of an inch. (I actually pulled threads from a quilt-shop quality fabric to see.)

On top of that, the A/B section must fit precisely with the C patch. And then the A/B/C section must fit precisely with the D patch. This is a block where you can really have challenges if your seam allowance goes haywire.

frame1 Lets Talk Seam Allowance: Back to School Lesson

My pieced A/B section was longer than the C patch, when they should have been the same.

Which is exactly what happened to me as I was making my first block on Monday.

foot1 Lets Talk Seam Allowance: Back to School LessonI used my Bernina quarter-inch-foot-with-guide, which I normally love and find to be very accurate.

foot2 Lets Talk Seam Allowance: Back to School Lesson

However, when I made the A/B section, it did not come out to be 9.5″ long. It was 9.75″ long. This was a problem.

foot5 Lets Talk Seam Allowance: Back to School Lesson

Why wasn’t it working? The answer lies in several factors that are often overlooked. Let me explain.

You may have what you think is a perfect quarter-inch seam. But…

?  ?  ?

  • Is the fabric you are sewing with the exact same weight as all of your other fabrics have ever been?
  • Is the thread you are using the exact same thickness as all the other thread you have ever used?
  • Is the pattern you are following exactly like every other pattern you have ever followed?

?  ?  ?

In all three cases, the answer is no. And one final, even more important question: Are your pieced sections fitting nicely with the other patches?

If the answer is no, here’s the bottom line: You must adjust your seam allowance to whatever project you are working on so that it is accurate for that project. Due to variances in weight of the fabric, weight of the thread, and type of seams you’re sewing (straight or  diagonal or some combination), you will need to alter your seam allowance depending on the project.

I solved the problem above by switching to a general purpose foot and moving the needle position so that when I lined the edge of the fabric up with the edge of the foot, I was taking a bigger seam allowance than before.

foot4 Lets Talk Seam Allowance: Back to School Lesson

I switched to a general purpose foot and moved the needle position to the right. See how the needle is not in the center of the foot? I line the edge of the fabric up with the edge of the foot for the seam allowance I need for this project.

It was only 2 or 3 threads bigger, as you can see below, but it made a huge difference. With the adjusted seam allowance, the A/B section came out to be 9.5″ just as it needed to be.

frame4 Lets Talk Seam Allowance: Back to School Lesson

It’s worth mentioning that I didn’t resew every seam. After resewing four of the six, the section measured 9.5″, so I stopped there. Unless you’re trying to win a major show, the difference between the patches is small enough not to matter.

foot6 Lets Talk Seam Allowance: Back to School LessonHere’s what I would suggest as you begin to make your Frame by Frame blocks. Sew an A/B section or two. Press them gently, making sure you’re not leaving a lip of fabric at any of the seams. Measure to see if the section is 9.5″ long as it needs to be. Adjust as needed.

foot7 Lets Talk Seam Allowance: Back to School Lesson

How to adjust: If your A/B unit is more than 9.5″ long (such as 9.75″ or 10″), you need to take bigger seam allowances. Being off by about 1/4″ means you should move over about 3 or 4 threads on each seam. This is a very small amount. Being off by 1/2″ means you should move over even more. As you adjust, remember that whatever change you make to the seam allowance is multiplied by six because there are six seams.

If your A/B unit is less than 9.5″ long (such as 9.25 or 9″), you need to take smaller seam allowances. You will need to unsew the seams and then resew them.

I’m sure you’re seeing why it’s a good idea to sew one or two blocks and get the seam allowance right before you make all 48 blocks! Nobody wants to go back and redo 288 seams (48 blocks x 6 seams in each = 288 seams).

blocks111 Lets Talk Seam Allowance: Back to School Lesson

Fabrics by Monaluna and Moda Fabrics

Here are my first blocks. The red and green fabrics are Moda. The other fabrics are organic Fox Hollow by Monaluna. These fabrics have a wonderful hand and I love the prints! Visit monaluna.com for lots of great 100% GOTS-certified organic cotton.

Of course there are other ways to adjust when things aren’t  fitting together just right. You can adjust your cutting: moving the line on the ruler just off of the fabric or just onto the fabric’s edge can make a big difference up or down. Sometimes this bit of adjustment is all you need.

As strange as this sounds, you can often increase your accuracy by shortening your stitch length. I never piece with stitches longer than 2.0 mm. The default stitch length on most machines is too long for piecing. Shorten up and see what happens.

Thanks for joining me for the Back to School lesson!


About Diane Harris

I'm Interactive Editor for Quiltmaker magazine in Golden, Colorado, USA. For six years, I've been writing pattern instructions and product reviews, and doing a host of other tasks necessary to help produce a national pattern magazine. Now I work remotely from rural Nebraska to generate some of our online content. I manage the QM Scrap Squad, our blog tours and our Quilt-Alongs. I have one of the best jobs in the world.
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27 Responses to Let’s Talk Seam Allowance: Back to School Lesson

  1. Ida says:

    I consider myself a new quilter. I did not know that thread and fabric were a factor. I had been practicing on scraps and using old thread. My real blocks were always off. In frustration, I had to piece things on the big side and cut them down. Now I know to test with the same fabric and thread I will be using in my project. Thanks for the great tip.

  2. Susie says:

    I use glow tape to write down the machine setting for different sewing machine feet even my walking foot so I can return to a “true 1/4″ . These stay on my machine.

  3. Barbara says:

    Wow….. such an eyeopener…. I really thought it was all my technique…. I carefully measure when cutting and sewing and still had problems. I am new to quilting and so appreciate this….this is probably one of the best tips I have gotten to date…..so nice to know that even the experienced quilters have trouble and would correct by the same method I use…. I always felt like I was cheating somehow. THANK YOU!!!!

  4. Kay Thomas says:

    My husband stressed the importance of accurate cutting when I was new to quilting and his sound advice probably has a lot to do with my continued interest/obsession in the craft. I would have been frustrated and given up because of sloppiness. My 1/4″ seams often remain a challenge to maintain and I keep a piece of 1/4″ graph paper near my machine when I feel the need to tweek my way back to accuracy. I place the foot edge on 1 line of the paper and adjust the needle to perforate the paper on the next 1/4″ line over. My challenge is keeping the edge of my seams lined up perfectly with the foot. And then of course there is the pressing…

  5. Christa says:

    Now I know why the star quilt I was trying to make did not fit together, I always thought a 1/4 ” seam was always the same Thanks so much for the lesson.

  6. gail says:

    Just another thought for consideration…. accurate and consistent cutting also makes a big difference. Even when we change the angle of the rotary cutter we may affect the cut piece by enough to throw things off! So much to remember in our fun world of quilting! :)

  7. Kathy Getz says:

    Great lesson. I have been helping a begining quilter cut and piece her first quilt. Left on her own before we got together she didn’t know how important a 1/4″ seam allowance is to the end result. This lesson will help me get her going with accuracy. I appreciate the easy ways to adjust seams. Thanks so much!

  8. Lynette Broomfield says:

    Diane. Really enjoy your lessons. I always sew at 3.0 stitches per in. Will try 2.0 and see if I am more accurate. Good tip. Someone once told me the length of your stitch depends on the size of your seam ripper so I went a 3.0 stitch length and have noticed my seams are wavy at times. I hate to give up my 1/4 inch foot but I do think it is not always accurate. So glad you moved to rural Nebraska

  9. Judy Konya says:

    This is so timely. I just finished the top of a quilt that I designed with Electric Quilt and I thought that the measurements were off. I realized that it was the seam allowance. Unfortunately too late. You saved me a lot of figuring for the next time I make this quilt. Also, when will I learn to make one or two blocks and measure, then make the rest???
    Thank you so much

  10. Valeria Wolff says:

    Thank you for your information. I have just one question-For the Bernina 440QE machine, would the moving of the needle one step to the right take care of this problem? Doing so, would it then become the famous “scant” seam allowance?

  11. Lois Rogness says:

    Great tips!

  12. Carol Hemmingsen says:

    Great lesson. I really like the quarter inch foot with adjusting the needle position. Easier to stay accurate throughout the quilt! Just have to remember where you put the needle position and reposition it after you turn off your machine!!

  13. Bonnie H. says:

    Great lesson! It’s amazing how a little mistake can make such a big difference.

  14. VickiT says:

    Great information and very helpful as well. Thank you.
    I just did my first large “real” quilt with the Quilting Gallery and their Beginner’s Quilt Along and found a few of my blocks were off when completed. I had to do some adjustments and about 3/4 of the way through the quilt along I too removed my 1/4″ foot with the guide on the side and started using my 1/4″ foot without guide and also as an extra bit of help, used the quilting notion I have that you put the needle into the hole in it and then it shows exactly where the 1/4″ spot is on the machine bed. Once I saw that, I put multiple layers of painters tape along the entire width of my machine bed and used that to follow along so I knew my stitching was straight as well. That was the trick that helped me tremendously as I did not have a block after doing that which had to be adjusted.

    Maybe I was lucky or maybe it worked this time for me since I was using fabrics which were from one entire collection of fabrics so they were each the same exact weight. I never gave any thought about the weight of your fabrics being used until reading this so thank you for the addtional help.

    Note: the reason for saying my first large “real” quilt is that all prior to this one were small baby quilts and done using large squares of fabric with machine embroidery rather than traditional pieced quilt blocks. Still they were quilts and very pretty, but they weren’t what I’d consider a real quilt because of the lack of piecing. Of course, maybe my thinking is wrong on that but as long as what I created is beautiful and the receiver of it loves it, then I am happy.

  15. Ranette Elledge says:

    Great information. I needed the reminder that especially on small pieces the inacuracies multiply very quickly and make a big difference when adding small pieced units to bigger pieces. I will be more careful and check often for fit.

  16. MarciaW says:

    I like all of your lessons. Jumping back to visit from the blog hop.

  17. Sandra Aiken says:

    Thanks for the great lesson.

  18. Rayne Garnsey says:

    great lesson!

  19. Kerry says:

    Great lesson on things that are often forgotten or not taken into account. I never thought about differences in fabric thickness before.

  20. Bea Morris says:

    Great lesson, I have sewed since I was little, and I think all sewers should at least once a year go back to the basic set of rules and reread them, and practice them. Thanks

  21. Patricia Hall says:

    Thanks for this helpful tutorial. I have often wondered why sometimes my blocks are not matching. Now I know some of the reasons. Thanks!!

  22. Dawn Hollingsworth says:

    Great tips!! I never would have thought about fabric weight! Terrific lesson! Thank you!! :)

  23. Ros says:

    Thank you so much have learnt a great lesson tonight.

  24. Mike says:

    I am a beginning quilter and have just made piecing adjustments as I went along. Now I can get it right from the start.

  25. Colette says:

    Never too old to teach a dog new tricks. I wondered how this happened to me all the time. Thank heavens it’s not entirely me, but other factors too!

  26. Kaye M. says:

    Thanks for the piecing lesson. Its great to have this before anyone gets very far on this project. I often have that little lip of fabric at the seam that didn’t get pressed quite flat that you mentioned. I think I need to do more careful pressing.

  27. marjorie says:

    Great lesson!!! So many important things are addressed. Thanks!

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