IF THE COTTON GATHERS AT THE BOBBIN SIDE OF FABRIC WHEN SEWING WHAT ARE THE POSSIABLE REASONS

There could be several reasons why the cotton is not being pulled from the bottom to the top. Here are some things you can try:

1. Check the bobbin: Make sure it is wound properly and inserted correctly in the bobbin case. The thread should be going in a counterclockwise direction.
2. Check the needle: Ensure that the needle is the correct size for the fabric you are using and is inserted correctly. A dull or bent needle can cause problems with thread tension.
3. Check the tension: Make sure the top and bottom thread tensions are correctly set. The thread should be able to move freely through the machine without being too loose or too tight.
4. Check the feed dogs: The feed dogs should be in the up position and moving the fabric smoothly through the machine. If they are not working properly, the fabric may not be moving through the machine correctly.

If none of these solutions work, there may be a mechanical issue with the machine that requires professional attention.

Yes it usually is caused by lack of bobbin tension. The bobbin tension doesn't usually change by itself though, so check for other reasons before changing it. Can you feel some tension when you pull the bobbin thread?
Is the bobbin cotton threaded correctly through the bottom tensioner? Is it the same size as the top cotton?
Is the top cotton correctly threaded and freely moving through its path? How much tension is felt when you pull it?
Good luck finding the problem.

Bobbin Tension How and Why Tension is Adjusted

Understanding Bobbin Tension

Understanding Thread Tension Threads

Sewing Lesson 10 How to Fix Tension on Your Sewing Machine

Bobbin tension depends on the thickness of the fabric that you're sewing on. A cotton fabric should have medium tension...but a heavy wool would need a looser tension. Best way to get the tension right is to take a few stitches, then look at the bottom side of the fabric. If the threads are loose, then tighten the tension one notch or number. Sew a few stitches, then test again. If the fabric is pulling up tight, then loosen the tension and check again. Top stitches and bottom stitches should both be the same.

Stitch length of 4, loosen your top tension by half a number and always pull up the bobbin threads.

If you need to gather yards of fabric then get a gathering foot. Janome make one - it looks like this


This foot is for creating soft gathers in lightweight fabrics. The underside of the foot is raised behind the needle and has a thick bar in front of the needle to gather the fabric. This works great to create the gathers as you sew. You can also gather and attach a ruffle onto a flat piece of fabric simultaneously, run the flat fabric through the top groove of the foot and the underneath fabric is gathered and stitched to the top piece, you need to keep the bottom piece feeding smoothly though so it takes practice to guide it evenly. Once mastered it is great to ruffle on valances and cushion frills.

Other option is use a ruffler foot, these will make a little ruffle every 12, 6 or 1 stitch so give a set result, and to obtain a more dramatic gather. They look like this.


The arm of the foot with a C'shape sits over the needle bar of the machine so it is moved up and down to activate the device. The little blade at the front moves backwards at regular intervals forcing a "tuck" of fabric into the feed to be stitched. Again you can ruffle and stitch to straight fabric at once but it is an art to master.

The weight of the fabric you are gathering is obviously the key variable, ginghams and poplins are lightweight so gather easily but if you need to gather something heavy like cordoroy it is going to be a battle and threads may break. If so, stitch two lines of gathers and don't try to do long runs, you'll just break a thread and have to start over.

Another good way is to zig zag over a length of perle cotton, taking care not to actually stitch the pearle at all. You can then gather up the fabric along it, this works well for heavier weights.

Are you threading the bobbin in correctly? the right size thread and needle for the fabric?

The tension for cotton is set the same way tension is set for any fabric:

1. The thread should pull freely with a small resistance before/after it goes through the needle, on many machines that's half way on the tension adjustment.

2. The bobbin thread when dangled by the thread with the bobbin inside the case should drop down a bit when slightly flicking your wrist like you do with a yo-yo. If it reels out to the floor the tension is too loose. If it doesn't drop at all it is too tight.

3. Now make sure you use the right type of needle. For cotton you want a "sharp" and for reg. weight cotton about a size 10 maybe 12.

Now take a piece of strap cotton material like you're going to sew a seem and sew with a wide zig zag. Example the top side and then the bottom. They should appear identical, flat with needle holes at each side where the thread disappears to the other side. You should see no loop where the threads over lap each other and the material should not be puckering in the middle.

If that is not what you see then think this way:

The TOP side of the stitch is effected by the BOTTOM thread. the bobbin tension.
The BOTTOM side of the stitch is effected by the TOP /needle tension.

Adjust the responding tensions until the stitch looks the same on both sides. Now you are ready to sew your cotton! :)

Check the bobbin tension too. It could be too tight. Make sure you are using the right size needle for the material as well. Sheer, thin fabric needs a smaller needle, thicker material requires bigger needles. Bobbin tension is the typical problem as most think to adjust the top tension but don't check the bobbin tension.

Is your quilt peices cotton? Cotton shouldn't cause as much trouble sewing along the edge but don't use too long of a stitch length else it will seem to gather up. Puckering side to side however is a tension problem usually. With sheerer fabrics that cause a problem sometimes you can put thin paper underneath, sew through both and then pull the paper off after sewing. (thin like the iron on type interfacing type fabric but like paper).

Check the bobbin tension and that the thread is tight around the bobbin. Make sure that the bobbin is in the right way around - the bobbin thread should double back on itself coming out of the bobbin holder.

Change needle
Clean under needle plate where feed dogs are for lint
Clean bobbin area for lint or loose threads
Rethread machine top thread make sure to get every thread guide
& bobbin
Check tension 3 or 4 is usually good