8 Tips to Improve Piecing Accuracy


We quilters are a precise bunch! And that's a good thing, because accuracy is everything when it comes to getting a great result on your piecing.

No one wants to cut up their favorite fabrics and labor over an A+ quilt block only to discover that it’s come out too small, or the pieces don’t fit together quite right. Luckily, a few go-to rules go a long way.

1. A Scant ¼” Seam Is a Quilter's Secret Weapon

Most quilt patterns call for a ¼” seam allowance, and they mean it! If your seam allowance is off by even 116″, it can make a big impact on the final quilt. Even a tiny degree of error can really add up over the course of a block. One safeguard here is to get in the habit of stitching a barely scant seam. That way your measurements account for the seam itself, and the fold in the fabric too.

Confusing? Maybe a little. Let's start with that perfect ¼”, then move on to the secret-weapon scant version.

How to get a perfect ¼” seam

We get it: It's way more difficult to achieve a true ¼” seam than you'd think. And you're not always set up for success either since it's common for the ¼” markings on your sewing machine or even your ¼” presser foot to be noticeably off. The only way to be sure you have an accurate seam is to stitch a ¼” seam following the presser foot and measure it with a clear ruler. Make sure your seam is right on the ¼" mark — you'll thank yourself later.

In the above image, the seam on the right was sewn following the edge of a ¼” presser foot, which resulted in a seam that was just on the outside of the ¼” marking. No good!

Scant ¼” seams

Here's where we get fancy:

Check out the seam on the left in the image above. To sew a scant team, make sure you can’t see the drawn line outside of the presser foot; instead, keep it just under the very edge of the foot. This small change will keep your seams just a couple of thread widths under ¼”, which will account for both the seam and the actual fold in the fabric when your press your seams under.

2. Press Smart!

First, make sure your iron is on the highest cotton setting, and don't be afraid to use some steam. If you’re working with fabrics that are cut on the bias, handle them with care so they don’t stretch while being ironed.

This is important: Make sure you're “pressing” and not “ironing.” That means placing your iron straight down on the fabric, not moving it back and forth like you're trying to get wrinkles out of a dress. Moving a hot steaming iron back and forth over your quilt pieces is almost guaranteed to stretch and distort them.

3. Starch Is Your Friend

Starching fabric before cutting and while pressing is one of the best ways to stay accurate. You'll notice that seams lay flatter and fabrics stay crisp throughout the piecing process.

Since starch makes fabrics stiff, it prevents distortion when you’re handling and pinning pieces. And it rinses right out in the wash when you're done. There are plenty of starches on the market, but one of our favorites is Mary Ellen’s Best Press Spray Starch.

4. Trim Away Tails and Dog Ears

Some blocks — like half-square triangles and quarter-square triangles — end up with little tails or dog ears of fabric that extend into the seam allowance. These just add bulk, so make sure to trim them off.

5. Use sharp tools

You might think you're being economical using tools that are past their prime, but you really aren't doing yourself any favors. Dull blades and needles make accuracy borderline impossible, so plan to get new tools for each quilt project.

6. Measure Twice, Cut Once

Ahh, one of our favorite mantras. Measuring correctly is critical, so read requirements carefully and make sure you have the right ruler for the job. Clear, non-slip rulers are best. You can also add adhesive gripper tape (such as Handi Grip Strips ) to help with slippage.

When you're cutting several units from the same piece of fabric, stop occasionally to make sure the fabric is still square.

7. Learn to Love Basic Math

There's no way around it: Quilters need math. So if you haven't done much division since high school, now's the time to get reacquainted. You'll need to understand how pieces add up to equal a total measurement on a block or quilt. And calculate how much fabric you’ll need to purchase. And determine how many strips to cut for your binding. You'll just need to know the basics, so get ready for a little number-crunching on the old calculator.

8. Square Up Blocks Only If Needed

Truth be told, if you cut and sew your blocks accurately, you may not need to square up your final block. But some patterns tell you to make blocks a little large and then trim them down to the exact size needed. Make sure blocks and block segments are the correct size before putting them together in your quilt. An acrylic ruler is your best bet for the most accurate squaring up.

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8 Tips to Improve Piecing Accuracy