How to Fix Bobbin Tension

April 23, 2020

Is your bobbin thread showing on the top side of your fabric? Are your stitches just looking wonky and not very strong or even? Sounds like your sewing machine tension is out of whack or your bobbin is behaving badly! Let’s talk about how to check to see if it is AND how to fix bobbin tension on your sewing machine.

This post is for the beginner who is somewhat comfortable with their machine and has been working along for a little bit without issue. You will learn how to check and fix bobbin tension if you are having stitch formation issues. ◉ The machines we are working with today have a bobbin case for their bobbins. The process of fixing tension is relatively similar for drop in bobbon style machines (like Brother, BabyLock, Janome brands). Look further down where the is and you’ll see more machine specific bobbin information there.


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up close photo of a sewing machine bobbin case

When stitches become weak, bobbin threads show on the top or thread bunches keep happening, getting to know more about the machine will help solve the problem. Since stitch formation is a relationship between the upper thread from the spool and the bobbin thread coming from the bobbin, both the upper thread and bobbin tension need to be looked at to solve problems.

Tension describes the amount of pull on the thread and correlates to the tightness of your stitches. Too much tension, the thread ends are pulled to far apart and the thread might snap. Too little tension, the thread will sag or not lay flat on the fabric because there is too much slack.

In this post, we are going to focus on the bobbin tension. Upper thread tension is easier to change, there is a little moveable dial on the upper left portion of the machine, along the path the thread takes from the spool to the needle. There are numbers on the dial, making it easier to make note of your upper thread tension. Adjusting the upper thread tension is one of the first places to look when trying to solve tension issues. I’m focusing on bobbin tension first because there is less information out there about it, we can delve into upper thread tension at a later date.

What Good Thread Tension Behaves Like:

The relationship between the upper thread and the bobbin thread will affect the quality and strength of the stitches your machine makes. In a well formed stitch, the threads meet together in the middle of the fabric and lock together evenly. You should not see your bobbin thread on the top of your project and you should not see the upper thread on the underside of your project.

When the bobbin thread is not tensioned properly, it will show in how the two threads appear on the fabric. You’ll likely find out that your tension is off by looking at a section of stitching that doesn’t look like how you were expecting it to. Maybe the bobbin thread is showing on the top or the upper thread is so loose it pulls out easily. Sometimes it’s on your nice, expensive project fabric! Let’s get the bobbin tension checked and fixed before it happens on your next project. 

Horizontal vs. Vertical Bobbin Cases:

Some machines, such as Singer and Bernina brands have their bobbins in cases within a bobbin race that holds the bobbin case in an upright, vertical position. The bobbin case needs to be removed in order to change to a new bobbin.

The inside of a sewing machine, bobbin case
The inside of my Bernina showing the bobbin race and case, as viewed from the front of the machine.

◉ Others, such as Brother and Janome brands have the bobbin laying horizontally, partially under the throat plate of the machine, usually not in traditional bobbin case but in a differently shaped bobbin case that stays in the machine most of the time. You can tell the difference between the machines not only by bobbin location, but also how the bobbin case does not need to be removed to change the bobbin.

Bobbin holder from Janome Sewing Machine
Bobbin case on a Janome, we’ll learn more below.

Check Bobbin Tension (so you can fix it later)

This first part is for machines that have a bobbin case that comes out of the machine in order to change the bobbin. For machines that you just drop the bobbin in, see ◉ below.

To start, pull out the bobbin case from your machine. You can pull on that little handle on the front of the case and it will pop out the machine. Gently drop out the bobbin and load in a freshly wound bobbin, following the directions in your sewing machine manual. A properly wound bobbin is also important to get good tension.

Do not put the thread through that extra little arm or coil sticking out (if you have one, mine does). That is used for any embroidery modules/ functions on your machine, it will interfere with the bobbin test and you will not get accurate results.

Next, place your index finger and thumb where the thread comes out of the case and pinch the thread. Holding your bobbin case about a foot over a soft surface in case it drops, flick your wrist in a downward motion so that the case moves down with you still holding the bobbin thread. The motion reminds me of playing with a yo-yo.

One of four things can happen:

1) Your bobbin falls out of the case and hits the soft surface. This doesn’t help us test tension or mean anything, it just happens when you start trying out this technique. Start over, it happens to everyone, including me, a LOT!

2) Your bobbin goes nowhere… Your fingers are still pinching the thread at the point where the thread comes out of the case. This means your tension is TOO TIGHT. Your bobbin thread cannot leave the case and this will not allow the bobbin thread to meet in the middle of the fabric with the upper thread.

3) Your bobbin falls down, almost to that soft surface you held it over. This means your tension is TOO LOOSE. The thread is just coming out way too fast and will bring your bobbin thread to the top of your fabric, where it does not belong!

4) Your bobbin falls only an inch or two below the point you have the thread pinched. This is GOOD TENSION! You want the bobbin case to hold onto the thread enough to catch its fall, but not so hard that it doesn’t move anywhere or fall more than those two inches.

This movement takes practice. I feel like a wizard waving a wand trying to perfect the wrist action. Swish and Flick. Anyone?

If anyone asks what you’re doing, just tell them the truth or tell them to bugger off! (That doesn’t sound too kind does it? I think I just like using the word ‘bugger’.) Or you could just tell them that you found a quick way to check and fix your bobbin tension…

To see this in action, here is a video:

How to Fix Bobbin Tension

Now that we understand how to check bobbin tension, let’s take a look at how to fix bobbin tension. Figure out if your tension is too loose or too tight. Then, following the instructions below, fix it!

On the bobbin case you will notice a very small, flat head screw. There may be other screws, but they will likely be Phillips head screws that are super tiny. Take a small screwdriver that will fit into the slot on the screw. After testing your bobbin, you should be able to determine if your bobbin tension is too tight or too loose.

Bobbin case tension adjustment screw
Close up of the flat head screw that adjusts the tension on the bobbin thread.

To tighten bobbin tension, turn the screw clockwise/to the right (‘righty tighty’) in very small increments. 1/8 to 1/4 of a turn (imagine a circle that is the head of the screw, only turn it 1/8 to 1/4 of the circle at a time).

Test the tension between each adjustment of the screw.

To loosen bobbin tension, turn the screw counterclockwise/to the left (‘lefty loosey’) in very small increments. 1/8 to 1/4 of a turn (imagine a circle that is the head of the screw, only turn it 1/8 to 1/4 of the circle at a time).

Turning the flat head screw makes the plate that it is attached to go closer or further away from the rest of the bobbin case. The bobbin thread travels between the plate and the case, so by adjusting the plate, you are adjusting the tension on the thread. Tension in this situation is really about the speed at which the thread comes out of the bobbin. Too slow and you’ll get a really tight bobbin thread, too fast and you’ll see the bobbin thread on top of the fabric. Both Bad!!!

Bobbin case from Bernina Sewing Machine
What the Bernina bobbin looks like out of the machine. Most bobbin cases look like this, even for other types of machines like commercial embroidery machines.

If you find that you have gone too far in one direction, just gently go back in even smaller increments. Keep testing until you like how the stitches are formed. After adjusting the tension, don’t touch the screw and be careful not to drop the case.

◉ For Drop in Bobbin Style Machines

For drop in bobbin style machines, testing is a little more hit or miss. First, make sure your machine is threaded properly. Then take a look at your upper thread tension dial. Looks something like this:

Upper thread tension dial on a sewing machine
The magic place to begin testing tension on a machine with a drop in bobbin. Also where you adjust the upper thread tension.

The upper thread tension dial should have a special mark next to one of the numbers. That mark is a good place to start testing out your bobbin tension, it is sort of the default setting for the upper thread tension.

In order to take the bobbin case out, you need to remove the throat plate. There are usually somewhat large flat head screws holding it down. They should be the only screws showing on the plate. Pardon the little focus issue, but that screw on the right is what the screws look like on the throat plate of the Janome machine.

Sewing machine throat plate
See that screw on the upper right corner? That is one that needs to be removed to take off the throat plate.

Showing the image below again so you see where the tension adjustment screw is when the bobbin case is still in the machine. You need to take the case out to adjust the tension, please don’t go sticking screwdrivers into your machine at random, especially if it is still plugged in!!!!

Bobbin holder from Janome Sewing Machine
Bobbin case on a Janome, visible after removing the throat plate.

Take a scrap piece of fabric and start sewing with a straight stitch or whatever stitch you were using when you discovered the problem. How do the stitches look? If the bobbin thread is too loose and showing on the top of the fabric, carefully tighten the flat head screw (shown below) to the right. If it is too tight and the upper thread is being pulled to the back of the fabric, loosen the screw by turning to the left. Remember, righty tighty – lefty loosey? It works here too.

Bobbin case from a Janome sewing machine
The bobbin case, removed from a Janome. This is a drop-in style bobbin case.

Keep adjusting that flat head screw in the proper direction until you have a balanced stitch that doesn’t show thread on the wrong side. Ignore the Phillips head screw, it doesn’t get touched for the tension.

Test, test, test, test, test!!!!

The only way to see if you have been successful on both types of machines is to TEST. Don’t forget to test out your tension between adjustments on scrap fabric!

How do you show your sewing machine some love?

Want to remember this? Post this How to Fix Bobbin Thread Tension Tutorial to your favorite Pinterest board!

Bobbin on purple fabric

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