Welcome to Lesson 6 of the HTVRONT E15 Embroidery Machine tutorial series. In Lesson 5, we covered bobbin thread tension using the drop test. Today, we're focusing on the other half of a balanced stitch: upper thread tension.
Before starting your embroidery project, you can use the built-in tension test pattern to check whether the upper thread tension is properly set. Correct thread tension creates smooth, even stitches on the front and helps prevent thread breaks, loose stitches, and bobbin thread appearing on the surface of your fabric.
In this tutorial, we'll walk through a complete upper tension check using the "I" test pattern, from preparing the test materials to reading the results and making fine adjustments. Let's begin.
Key Takeaways
Correct tension looks even on both sides — smooth stitches on the front, with the bobbin thread centered on the back.
The "I" test pattern is your diagnostic tool — a simple linear design makes tension problems immediately visible.
Check the back of the fabric, not just the front — most tension problems only show up on the underside.
Proper ratio: about one-third bobbin thread in the center of the stitch. Too wide means tension is too tight; too narrow means too loose.
Adjust in small increments — turn the tension discs or check spring slightly, then re-run the test.
Three adjustment points control the upper tension: two thread guide tension discs and one tension check spring.
Why Upper Thread Tension Matters
Upper thread tension controls how tightly the top thread is pulled through the fabric during each stitch. If it's too tight, the upper thread pulls the bobbin thread up toward the surface — causing puckering, distortion, and needle deflection. If it's too loose, the bobbin thread gets pulled up to the fabric's surface — showing up as loops, tangles, or bird-nesting.
When tension is correct, the upper thread and the bobbin thread meet in the middle of the fabric and lock together, forming a smooth, balanced stitch that looks clean on both sides.
Signs that your upper thread tension needs attention:
Loops or tangles on the top surface of the fabric
Puckering or wrinkles around the design
Bobbin thread visible from the front
Frequent upper thread breaks
Uneven stitch density
Step 1: Prepare the Test Materials
First, prepare your test fabric and stabilizer, then hoop them together evenly. Make sure the fabric is free of wrinkles, but do not stretch it too tightly. The fabric should lie flat and smooth in the hoop, without any tension from stretching.
Pro Tip: Use the same fabric and stabilizer combination that you plan to use for your actual project. Different fabric weights and stabilizer types affect how the thread behaves, so testing on the same materials gives you the most accurate result.
Step 2: Set the Embroidery Parameters
Next, select the "I" tension test pattern on the machine. Tap Pattern Select, then choose the "I" test design from the built-in pattern library.
Select the frame size that matches the frame currently installed on the machine.
Next, set the thread colors and run the Pattern Trace to make sure the pattern stays within the embroidery area.
Once everything looks correct, tap Ready then press the Start button to begin embroidering.
Step 3: Run the Test at a Low Speed
For the first test, we recommend using a lower embroidery speed. This makes it easier to observe the stitching and stop the machine quickly if anything looks unusual. A speed of 500–600 SPM is ideal for a tension test — you're not trying to break production records, you're trying to observe how the thread behaves.
Step 4: Check the Stitches from the Back
With proper thread tension, the center section should show about one-third bobbin thread.
While the two outer sections should show about two-thirds upper thread, the bobbin thread should stay centered and the stitches should look even and consistent.
Step 5: Identify Tension Issues
Now, examine the back of the stitched test pattern. The way the two threads share the stitch width tells you exactly what needs to be adjusted.
Proper Tension
If the bobbin thread takes up about one-third of the stitch width, the upper thread tension is properly set. The design looks clean and even on the front, and the back shows a balanced mix of both threads.
Upper Tension Too Loose
If too much upper thread appears on the back, and the bobbin thread section is too narrow, the upper thread tension is too loose. In this case, slightly increase the upper thread tension.
Upper Tension Too Tight
If too little upper thread appears on the back, and the bobbin thread section is too wide, the upper thread tension is too tight. In this case, slightly reduce the upper thread tension.
Step 6: Fine-Tune the Tension
The thread tension is controlled by three adjustment points: two thread guide tension discs and one tension check spring.
Adjusting the Tension Discs
To increase the tension, slightly turn the tension discs counterclockwise to decrease the pressure.
Turning it clockwise increases the pressure, while turning it counterclockwise reduces the pressure.
Adjusting the Tension Check Spring
When adjusting the tension check spring, turning it clockwise increases the pressure, while turning it counterclockwise reduces the pressure.
⚠️ Small adjustments only: Make only a small adjustment each time. Avoid making large changes all at once — a quarter-turn or less per adjustment is typically enough. Over-tightening the tension discs can cause thread breaks; over-loosening can create bird-nesting.
Step 7: Run the Test Again
After making an adjustment, embroider the "I" tension test pattern again. Turn the fabric over, and check the ratio of the bobbin thread to the upper thread.
When the front of the "I" tension test pattern looks smooth and the bobbin thread appears in about one-third of the stitch width on the back, the thread tension is properly set.
Iterate as needed: It's normal to run the test pattern 2–3 times before finding the correct tension. Each adjustment shifts the balance slightly. Take your time — dialing in the tension on a scrap piece saves you from ruined projects later.
Quick Tension Checklist
Run through these points before starting any embroidery project:
✅ Test fabric and stabilizer hooped evenly, wrinkle-free
✅ Fabric not over-stretched in the hoop
✅ "I" tension test pattern selected
✅ Frame size matches the installed hoop
✅ Thread colors set and Pattern Trace run
✅ Test run at a lower speed (500–600 SPM)
✅ Back of the stitch inspected for the 1/3 bobbin thread ratio
✅ Tension adjusted in small increments if needed
✅ Test pattern re-run after each adjustment
✅ Front and back both look even and clean when finished
Tutorial Video
Prefer to watch rather than read? Follow along with this quick upper thread tension check tutorial for the E15 embroidery machine:
Conclusion
You've now completed a full upper thread tension check using the "I" test pattern on the E15 embroidery machine. This is one of the most valuable diagnostic skills you can build — with a single test stitch-out, you can catch and fix tension problems before they ruin a real project.
Make this tension check part of your regular setup routine, especially when:
You're switching to a different thread weight or fiber type
You've re-threaded multiple needle positions
You're working with a new fabric or stabilizer combination
You've noticed any tension-related problems in recent projects
In the next lesson, we'll cover How to Import a Design from USB Drive — how to bring custom embroidery files into the E15 machine and get them ready to stitch. This is the skill that opens up your design possibilities beyond the built-in pattern library, so you can work with your own artwork, downloaded designs, or client-supplied files.
How often should I check upper thread tension on the E15 embroidery machine?
Check tension whenever you change thread weight, fabric type, or bobbin thread, and any time you notice stitching problems. With the same setup, the correct tension stays consistent across many projects. But if you switch from a 40-weight cotton thread to a 60-weight polyester thread, or from a lightweight knit to a heavyweight denim, expect to recheck and possibly re-adjust the tension. Running the "I" test pattern takes less than a minute and confirms everything is dialed in.
What should I look for when checking the back of the "I" test pattern?
Focus on the ratio of bobbin thread to upper thread across the stitch width. With correct tension, the bobbin thread forms about one-third of the stitch width in the center, with the upper thread making up the remaining two-thirds on the outer edges. If the bobbin thread section is too narrow (too much upper thread showing), tension is too loose. If it's too wide (too little upper thread showing), tension is too tight.
Which adjustment point should I turn first — the tension discs or the check spring?
Start with the tension discs first. The two tension discs handle the majority of the tension adjustment, and turning them by a small amount typically gets you very close to the correct setting. Only if you've adjusted the discs and still can't reach the right balance should you move on to the tension check spring. This order prevents over-adjusting the system and keeps the process manageable.
Can I skip the tension test and just start embroidering my project?
You can, but it's not recommended — especially on important projects. The "I" test pattern takes less than a minute and uses very little thread or stabilizer. Skipping the check means any tension problem will only show up after you've already stitched part of your actual design — and by then, you may have wasted fabric, thread, and time. For anything you care about, run the test first.
Why does my tension test look different on different fabrics?
Fabric weight, weave density, and fiber content all affect how the upper and bobbin threads interact. A lighter fabric may pull up more easily under tension, while a heavier fabric holds stitches more firmly. This is why testing on the actual fabric you plan to use is so important — a setting that works perfectly on cotton jersey may need adjustment on denim or canvas. Always test on a scrap piece of the same fabric before starting the final project.
What if adjusting the tension doesn't fix the problem?
If tension adjustments don't resolve the issue, check the following in order: (1) Make sure all threads are properly routed through the correct guides and tension discs. (2) Verify the bobbin tension using the drop test covered in Lesson 5. (3) Check that the needle is fully seated, undamaged, and appropriate for the fabric. (4) Confirm the stabilizer is suitable for the fabric weight. In many cases, what looks like a tension problem is actually caused by something else in the setup.
Keep Learning
Want to master more E15 embroidery techniques and grow your business? These guides will help:
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