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How to Make the Perfect Quilting Seam

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It is a universal truth that seam allowances for quilting must all be precisely one-quarter inch.

Have you ever had this happen to you?

  • Your 12’x12” quilt block measures 11.5″ x 11.5″.
  • Your quilt top won’t have seamlines.
  • Triangles are impossible to sew correctly.

What’s the problem?

Let’s suppose you follow the instructions in the quilt pattern to make a 12’x12” block. The 1/4″ piecing foot has been used and the seam allowance measured to be a perfect 1/4″ from the seam to its raw edge. When the block is completed, it measures 11″ x 11.

Your seam allowance may be the reason your quilt blocks are not coming out as you expected. You don’t need a 1/4 inch seam allowance. Instead, you only need a 1/4 inch seam allowance.

When I first heard the term “scatter 1/4″, I was shocked. I have a 1/4 inch foot. What the heck is a scant 1/4?’ seam? I quickly ignored the information and began making quilts using a 1/4” foot and following my machine’s seam guide. It sounds reasonable.

It turned out that I had a problem with one of my machines and I was having trouble maintaining consistent block sizes. My needle falls slightly to the left, creating a greater distance between the edge of 1/4” my foot and my needle. To get a precise scant 1/4″ seam allowance, I need to know exactly where my needle is located.

What is a 1/4″ Scant Seam Allowance? Why is it important?

The seam shrinkage of a seam is reduced by pressing the seam allowance to one side. Shrinkage is greater for blocks with more seams. As you begin to assemble blocks across a quilt, the problem only gets worse. Before you know, your individual quilt blocks will have shrunk and affected the overall quilt top size.

You will need a seam allowance that allows this little amount of shrinkage. Although a thread’s length may not seem like much, it can add up quickly. This is why you should use only 1/4 inch seam allowance to ensure consistent seams that your blocks line up.

It All Starts with the Thread

Before we can talk about quarter-inch feet or 1/4″ seam allowances, we need to first discuss thread and why it is important.

You will find a few thread options at your local big-box sewing and craft shop: Gutermann or Coats & Clark. These threads are great for general sewing, but they’re a bit thicker than finely spun quilting threads like Aurifil 50 wt.

Quilting can be difficult due to the fact that the thread takes up some fabric space. Aurifil is a finely spun brand that helps to reduce bulk when piecing.

A finely spun thread combined with a 1/4″ seam ensures perfect 1/4″ seams every time.

Create an Accurate 1/4” Seam Allowance guide

It is simple to find a 1/4″ seam allowance. Scroll down once you have located a scant 1/4″ seam on your machine.

  1. Slowly lower the needle so that it measures 1/4 inch from the ruler’s 1/4″ mark. Mark the machine’s bed with one of these methods.
  2. You can also try this method. Place 1/4″ graph paper on the far right edge of your presser foot. Slowly lower the needle to the right of the 1/4″ line. Mark the machine’s bed with one of these methods.
  3. To line up just 1/4 inch seam allowance, I prefer to use a seam gauge (see above). The template should be placed under the needle. Once the template is in place, the needle should be dropped through the tiny hole to determine the exact location for a 1/4″ seam allowance. To create a seam guide, follow the steps above.

Below are links to some of my favorite seam gauges. The Ideal Seam Gauge from Sew Very Smooth is what I use, but both are equally accurate.

Making a mark

Once you have a rough idea of where your 1/4″ seam allowance is, you can create a guide.

Here are some ideas I tried with success.

These methods will help you make your own seam guides

  • Blue painter’s tape can be used to make a stack of 2-3 layers. This will serve as a guideline for the fabric.
  • Sticking down a piece moleskin (for foot blisters) is another way to mark the seam allowance. It has enough thickness and a sticky back to serve as a guide. (affiliate)
  • Use a Sharpie to mark a line on the sewing machine bed.
  • These Seam Guides are great because they can be easily removed and reused over and over. (affiliate)

Whatever method you use, it will work so long as the guide is placed in front of your feed dogs. This will prevent the seam guide’s interference with your feed dogs while you sew.

The Seam Allowance:

Once you have created a 1/4″ seam allowance on your machine, you will need to test it.

Mark a red line in the middle of a 5” rectangle of white fabric. To demonstrate the difference, sew 1/4″ seams on one side and 1/4″ on the other. Although it is subtle, there is a noticeable difference.

A seam allowance test is a good idea. Below is an image that shows a 1/4 inch seam allowance. It is exactly right on the mark. You could lose some fabric if you use 1/4 inch seam allowance when piecing.

This happened to me recently while I was making a challenge block in my guild’s quilting group. The finished block was almost one inch off the seam allowance because I used 1/4″ seam allowance. Knowing that this block would be used in a quilt by someone else, I wasn’t sure what to do. After a while, I thought about ripping out all my seams and starting again.

I managed to save the block by blocking it and wetting it. It was not exactly the right size. This will never happen again.

Below, you can see the subtle difference in 1/4″ seam allowance. This tiny space allows for shrinkage caused by thread width and pressing.

A sewing machine that has an adjustable needle position can help you achieve a consistent 1/4″ seam allowance. You can try several techniques to find the one that works for you.

We All Sew also uses a Patchwork Seam Guide in this post.

You can take your time to determine the best way to achieve the perfect 1/4″ quilting seam allowance. You’ll soon feel comfortable enough to tackle more difficult blocks. The possibilities are endless.

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