Loops at the bottom when sewing: 7 reasons and how to fix them yourself

The problem with the formation of loops on the wrong side of the fabric is one of the most common sewing machine problems that both beginners and experienced craftsmen encounter. Looping thread from below not only spoils the appearance of the seam, but can also indicate serious damage to the mechanism. In 80% of cases, the cause can be eliminated independently, without resorting to the services of a service center.

Most often, incorrect settings or wear of consumables are to blame, but sometimes the root of the problem lies in mechanical damage. For example, in cars Janome and Brother loops at the bottom often appear due to the broken tension of the upper thread, and Singer older models - due to wear of the shuttle stroke. In this article, we will analyze all the possible causes, give step-by-step instructions for diagnosis and repair, and also tell you how to prevent the defect from reoccurring.

It is important to understand that nature of the loops may suggest the direction to look for the problem. For example, large loose loops are usually connected to the top thread, and small tangled ones are usually connected to the bottom thread. If the loops are formed irregularly, it is worth checking the synchronization of the movement of the needle and the shuttle.

1. Incorrect upper thread tension is the most common cause.

In 60% of cases, loops from below arise due to loose upper thread tension. This can happen after changing threads, cleaning the machine, or accidentally turning the dial. On modern electronic models (for example, Brother Innov-is NS80E) the tension is adjusted automatically, but even there failures occur.

To check tension:

1. Raise the presser foot and pull the thread out of the needle.
2. Pull the thread - it should come out with slight resistance.
3. If the thread slides freely, increase the tension (turn the regulator clockwise).

On older mechanical machines (e.g. Chaika-132M) the tension regulator often goes sour. In this case:

1. Apply engine oil to the governor shaft.
2. Gently roll it back and forth 10-15 times.
3. Wipe off excess oil with a tissue.

⚠️ Attention: On machines with automatic tensioning (e.g. Juki HZL-F600) manual adjustment may throw off the calibration. First try resetting to factory settings through the menu Settings → Reset → Tension Default.

Make sure the thread is correctly threaded into the tensioner|

Check the tensioner spring for wear |

Clean the tension disc from lint and dust|

Test tension on a piece of fabric -->

2. Bottom thread problems: bobbin case and hook

If the upper thread is adjusted correctly, but loops still form at the bottom, the reason lies in bobbin thread. Most often the culprits are:

• 🧵 Incorrect threading of the bobbin (the thread is caught on the edge or twisted).
• 🔧 Wear of the bobbin case spring (especially important for machines over 5 years old).
• 🛠️ Damage to the shuttle (scratches, chips, deformation).
• 🌀 The bobbin size does not match the machine model.

For diagnostics:

1. Remove the bobbin case and check how the thread comes out when turning the handwheel by hand.
2. If the thread is pulled out jerkily, the problem is in the cap or shuttle.
3. Inspect the shuttle for burrs (even microscopic scratches can tear the thread).

At the cars Janome Memory Craft and Bernina A specific problem is often encountered: the bobbin case is “sucked” to the hook due to the magnetic field. In this case it will help:

1. Cleaning the shuttle from metal dust.
2. Replacing the plastic cap with an original one (non-Chinese equivalent).

How to check the shuttle for wear without disassembling the machine?

Turn the flywheel by hand and listen: if you hear a metallic grinding or clicking sound, the shuttle needs to be replaced. Also inspect the junction of the shuttle and the needle plate: if lint or thread accumulates there, this is a sign of a loose fit.

3. Wear or incorrect needle selection

A needle is a consumable item that many people forget to change on time. Dull or bent needle not only breaks the thread, but can also cause loops at the bottom. This is especially true when working with dense fabrics (jeans, leatherette) or when using cheap Chinese needles.

Signs of needle problems:

• 📌 Loops appear at equal intervals (every 5-10 stitches).
• 🧶 The thread breaks when thick fabric is punctured.
• 🔍 There are visible hangnails on the needle or it bends when pressed.

Recommendations for choosing needles:

Fabric type	Recommended needle type	Needle size	Replacement frequency
Cotton, linen	Universal (H)	80/12	After 8 hours of work
Jeans, canvas	For jeans (H-J)	100/16	After 4 hours of work
Knitwear, elastane	With rounded end (H-SUK)	75/11	After 6 hours of work
Leather, leatherette	For skin (H-LR)	110/18	After 2 hours of work

⚠️ Attention: Needles Schmetz and Organ They last 2-3 times longer than their Chinese counterparts, but even they need to be changed after the specified operating time. A bent needle cannot be “straightened” - this leads to imbalance of the shuttle.

4. Thread and needle mismatch

Even if the needle is new and the tension is adjusted, loops at the bottom may appear due to incorrect combination of thread and needle. For example, a thin thread (#40) in a thick needle (90/14) will dangle in the eye, creating loops. And vice versa: a thick thread (#30) in a thin needle (70/10) may not pass freely, tear and form tangles on the wrong side.

Selection rules:

• 🧵 For thin fabrics (silk, chiffon) use threads #60-#80 and needles 60/8-70/10.
• 👖 For medium fabrics (chintz, poplin) - threads #40-#50 and needles 80/12.
• 👕 For thick fabrics (jeans, gabardine) - thread #30-#40 and needles 90/14-100/16.

Pay special attention to the quality of the threads:

• 🔴 Cheap threads (for example, "Ideal" or "Leningrad") often have uneven thickness, resulting in loops.
• 🟢 Recommended brands: Gütermann, Mettler, Madeira.
• 🔵 For overlock and cover stitch, use special Teflon-coated threads.

5. Mechanical faults: shuttle, hook-race, engine

If all of the above measures do not help, the problem may lie in mechanical part of the machine. The most common breakdowns:

• 🔧 Wear of the hook-race. Over time, the grooves expand, and the shuttle begins to “walk” without having time to pick up the thread.
• 🛠️ Bent shuttle shaft. Often occurs after a car falls or a strong impact.
• ⚙️ Wear of engine bearings. Leads to uneven running and skipped stitches.
• 🧲 Demagnetization of permanent magnets (in machines with a vertical shuttle).

Diagnosis of mechanical problems:

1. Remove the needle plate and hook cover.
2. Turn the flywheel by hand and watch the shuttle move:
   • If it “sticks” in extreme positions, there is a lubrication problem.
   • If play of more than 0.5 mm is visible, the hook-race is worn out.

Check the synchronization of the needle and the shuttle: at the moment of piercing the tissue, the nose of the shuttle should be 1.5-2 mm above the eye of the needle.

In industrial machines (Juki DDL-8700, Typical GC6-2>) a specific breakdown often occurs - shuttle shaft cam wear. In this case, the shuttle does not reach the extreme point and the thread is not caught. The solution is to replace the shaft or cam (the part costs ~1500-2500 rubles).

⚠️ Attention: If you feel a “step” or jamming when turning the flywheel by hand, stop using the machine immediately! This is a sign of serious damage (such as a broken tooth on the main shaft) and further work may cause permanent damage.

6. Electronic failures and firmware

In modern computerized machines (Brother Innov-is XP1, Janome Horizon MC15000) loops from below may appear due to firmware or sensor failures. For example, if the shuttle position sensor gives incorrect readings, the machine incorrectly calculates the moment to pick up the thread.

Signs of electronic problems:

• 🖥️Loops appear only with certain stitches (for example, with a zigzag).
• 🔄 After rebooting the machine, the problem temporarily disappears.
• 📶 Errors like E6, U3 or Check Thread.

What to do:

1. Reset settings to factory defaults (Menu → Settings → Factory Reset).
2. Update the firmware through the manufacturer's official website.
3. Check the sensor contacts (they often oxidize after a long period of inactivity).

For Brother Innov-is series machines, after updating the firmware to version 2.10+, the shuttle calibration may be lost. In this case, manual configuration is required via the service menu (access code: hold Menu + Start/Stop 5 seconds).

7. Prevention: how to avoid loops at the bottom

To prevent the problem from recurring, follow these rules:

• 🧹 Cleaning after every project. Remove lint from the shuttle compartment with a brush and vacuum cleaner.
• 🛢️ Lubrication once every 3 months. Use only special sewing machine oil (eg Singer Oil).
• 🔄 Replace the needle every 8 hours of operation. Even if the needle looks normal, its point becomes dull.
• 🧵 Storing threads in a closed container. Dust and moisture make threads brittle.

For industrial machines additionally:

• 🔧 Check the gap between the hook and hook-race every 6 months (tolerance: 0.05-0.1 mm).
• 🛠️ Lubricate the engine bearings once a year (partial disassembly is required).

💡

Regular machine maintenance reduces the risk of bottom hinges by 90%. Most “breakdowns” are associated not with wear of parts, but with non-compliance with operating rules.

FAQ: Frequently asked questions about bottom hinges

Why do loops appear only on thick fabric, but everything is fine on thin fabric?

This is due to discrepancy between the speed of tissue advancement and the speed of the shuttle. When sewing dense materials, the machine engine experiences increased load, and if the drive belt is stretched or loosened, the shuttle does not have time to grab the thread. Solution:

1. Reduce sewing speed.
2. Check the drive belt tension (on mechanical machines).
3. Use a needle 1-2 sizes larger (for example, 100/16 instead of 90/14).

Can a universal needle be used for all types of fabrics?

Technically it is possible, but this will lead to:

• Loops on thin fabrics (needle too thick).
• Skipped stitches on thick fabrics (the needle is too thin).
• Rapid wear of the needle and hook.

For knitwear, be sure to use needles with a rounded tip (H-SUK), otherwise loops and skipped stitches are guaranteed.

How do you know if the shuttle needs replacing?

Signs of critical shuttle wear:

• Loops appear even after replacing the needle and adjusting the tension.
• When turning the flywheel by hand, a metallic clang is heard.
• Deep scratches or chips are visible on the surface of the shuttle.
• The shuttle “sticks” in extreme positions.

Shuttle service life:

• Household machines: 5-7 years with regular maintenance.
• Industrial machines: 2-3 years (when working 8 hours a day).

Why did the hinges get even worse after cleaning the car?

Probable reasons:

• You've lost the setting synchronization of needle and hook (for example, the shuttle stroke was shifted during assembly).
• Too much oil got in and it is now sticking to the shuttle.
• Damaged lower thread tensioner spring when cleaning the bobbin case.

Solution:

1. Wipe the shuttle and hook-race with a lint-free cloth.
2. Check whether the hook has moved relative to the needle (the gap should be 0.1-0.3 mm).
3. Adjust the bobbin thread tension (in the bobbin case).

Which cars are least susceptible to this problem?

According to statistics from service centers, owners least often complain about bottom hinges:

• Janome Memory Craft 15000 (due to the system ACUFeed, which synchronizes the movement of the fabric and the shuttle).
• Bernina 770 QE (uses unique shuttle CB Hook with increased resource).
• Juki TL-2010Q (industrial mechanism with minimal backlash of parts).
• Pfaff Creative Icon (system IDT automatically adjusts tension depending on the fabric).

However, even these models require regular maintenance!