| Sewing Patterns for the Modern Woman - Blog Post: Four Tips for Serging Bulky Knit Fabrics

Four Tips for Serging Bulky Knit Fabrics

By Allie

Allie is the co-founder of Indiesew and creator of all things pretty on the site. Follow Allie and receive other Indiesew updates by subscribing to the blog. | Four Tips for Serging Bulky Knit Fabrics

At my family’s sewing reunion this summer, my sister ran into a sewing hurdle I couldn’t begin to help her with. She’s an experienced sewist, especially when it comes to knits, but serging the seams of her Lane Raglan just wasn’t working.

She was using a lovely, soft French terry she purchased from The Fabric Store on our first trip to LA together. It was a thick knit fabric with a lovely looped texture. But the seams of her raglan tee were appearing wavy and stretched out. We both agreed there must be a tension issue with her serger, but when she asked for more help I responded with an unhelpful shrug.

In truth, I had never seen a wavy serged seam come off my own trusty serger. Up until this fall, I also hadn’t done much serging of bulky knit fabrics like sweater knits, French terry, and sweatshirt fleece. But over the last few months I noticed a few other sewists having this same issue my sister had. And then one fateful evening when I was attaching the waistband to my Jasper Sweater, it happened to me.

I played around with the knobs and dials on my serger for what felt like hours until I finally found a solution. It turns out the issue didn’t have anything to do with tension.

In my experience, the dreaded wavy seam is most often a result of serging more than two layers of fabric together like when attaching cuffs, waistbands, and neckbands. In this tutorial, I’m serging four layers of our Black and White Aztec Ribbed Knit together.

Serging Bulky Knit Fabrics | Indiesew Tutorial

For this tutorial, I’ll be demonstrating on my Brother 1034D. Be sure to read your serger manual to best understand how the different settings on your serger affect the stitch. If you’re on the fence about purchasing a serger, check out Four Signs You Should Invest in a Serger.


Anatomy of a Serger

First, let’s learn a bit about the anatomy of the serger. Below is an image of what the three dials on the side of the Brother 1034D are used for. For most fabrics, I keep these dials at the default settings as noted by the numbers within grey rectangles.

Anatomy of a Serger |

Below is a photo of what a thick knit seam looked like after being serged using the default settings. Not pretty. 

Stretched Out Seam | Common Serger Problems

Now, let’s adjust these settings for a better serged seam.


1. Increase the stitch width.

For bulky knits a wider stitch makes a noticeable difference in how flat the seam will lie after serging. I increase my stitch width to the second-to-widest setting for thick knit fabrics.

 Serger Troubleshooting | Increase Stitch Width


2. Increase the stitch length.

I also find that the serger's longest stitch length results in a smoother serged seam when sewing with bulky knits. I tested out this theory by decreasing the stitch length to its lowest setting and found that it increased the waviness of the seam drastically.

 Serger Troubleshooting | Increase Stitch Length


3. Increase the differential feed ratio.

The differential feed ratio is perhaps the most important setting to play with for different fabric types. If your serger has differential feed, that means that its two sets of feed dogs can move at different speeds. The ratio is the rate at which the front feed dogs move over the rate at which the back feed dogs move. So a higher differential feed ratio means that the front feeds will feed your heavy knit fabrics through the needles a bit faster than the back ones. This factor alone will prevent stretching of heavy knit fabrics. I increase my differential feed ratio between 1 and 2, right around 1.5.

 Differential Feed Ratio | Increase for Bulky Knit Fabrics


4. Press the seam with a hot steam iron.

For those brand new to serging with knits, this last step might not be as obvious as it sounds. I’ve received many a frustrated email from sewists who simply cannot achieving the perfectly flat serged seam they’re looking for. I always suggest pressing the serged seam with a hot steam iron (use the appropriate settings for your fabric) as a last ditch effort. And in my experience, it almost always does the trick. Hot steam has the magical ability to snap stretched fabric back into place and smooth out those wavy seams.

Press Serged Seam | Sewing With Thick Knits

For the steps above I kept my serger’s tension dials as pictured below.  You may need to adjust your serger’s tension (especially the upper and lower looper) depending on your fabric type.

Indiesew | Serger Tension Settings

And this is what my new serged seam looks like:

Flat Serged Seam | Indiesew Knit Tutorials

Since every serger and fabric is different, I recommend playing around with these settings until you achieve the seam you’re looking for. Be sure to take note of the settings so you don’t forget them when you return to a similar project in the future.

We’ll have more thick knit fabrics coming to the shop very soon, folks! If you’re interested in finding a pattern well suited for these types of knits, take a look at the Bethioua, Jasper Sweater, or Sophie Cardigan.

Happy serging! 

Pin It

We've created a Pinterest friendly image so that you can save this post for later, when you need it:

Find out how to avoid the dreaded wavy seam when sewing thick knit fabrics like French terry, sweater knits and sweatshirt fleece. |

Leave your comment

In an effort to reduce spam, you must be logged in to leave a comment. Please log in or create an account.


No comments yet, be the first to leave some feedback!

    Browse Related Posts

    Want more sewing content like this?

    Receive the latest posts, tutorials, news, updates, deals and announcements right to your inbox!

    Emails are sent about once per week, unsubscribe anytime.

    We'll always respect the privacy of your e-mail address.