THREAD GET BUNCHED UP UNDERNEATH THE FABRIC, THE STICHES SEEM TO BE INCOMPLETE THE TOP LOOKS GOOD THAN I TURN IT OVER AND THE THEAD IS BUNCHED AND LONG LOOPS OF THREAD ARE LEFT. THANKS LOU

hi Lois.
this is all i could find out.
Check Your Tension Settings. Looping underneath the fabric usually occurs when there is not enough tension in the needle thread to pull the bobbin thread. Sometimes thread bunching can be caused by something as simple as the tension dial being inadvertently turn.
or try this link.
WHY IS THREAD BUNCHING UNDERNEATH MY FABRIC
or this one,
Sewing Machine Thread Bunching Up Here Why .
if you go to this link a little window might open up in the middle of the page just close the little window down.
or this.

The bobbin thread is bunching up Google Search

Bird nests (also called thread nests). Most common cause is because the presser foot is not Raised when the top thread is being threaded.

What causes Bird Nests Superior Threads

Birds nest under the fabric big loops of thread top side looks good...

Sewing Machine Thread Bunching Up Here Why

..

Thread nests (also called bird nests).

Remove the top thread.
ALWAYS RAISE the presser foot and rethread from the beginning.


Birds nest under the fabric big loops of thread top side looks good...

What causes Bird Nests Superior Threads

Susan--
Easy peasy, once you know the problem and how to fix it. It's called "bird nesting" or "thread nesting" or what I refer to as thread "barfs."

Install a brand new needle.
Remove all the thread from the machine.
**ALWAYS RAISE** the presser foot and rethread the top thread.
Verify the top thread path is correct.
Install and thread the bobbin case, make sure it is correct.
Set the top tension to the midway point.

Now retest your machine. Birds nests gone? You may need to tweak the top tension because the factory standard changes due to age and use.

FWIW, problems appearing under the fabric are an issue of the top thread. Thread problems appearing on top of the fabric is a bobbin issue.

What causes Bird Nests Superior Threads

Birds nest under the fabric big loops of thread top side looks good...

WHY IS THREAD BUNCHING UNDERNEATH MY FABRIC

Read this hope it helps

http://www.threadsmagazine.com/item/4302/understanding-thread-tension/page/all

First thing: install a brand new needle.
Second: remove upper thread. RAISE the presser foot and rethread from the beginning. Set upper tension to the midway point between high & low numbers.

These links may be helpful:

Sewing Machine Thread Bunching Up Here Why

5 Common Causes of Birdnests

Why Do Get Bunched Up Thread Under My Fabric

WHY IS THREAD BUNCHING UNDERNEATH MY FABRIC

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Skipped stitches is usually indication that needle is blunt or burred.
Or if you are using a sharp needle on knit fabrics it may also skip a little.

Not sure what you mean by "change weight of material" - do you mean you are sewing applique and going from one fabric weight onto another? or different sewing projects?

It is a good idea to change your needle for each new project (4-6 hours sewing time max) and choose the right type of needle and size for your project.

However, the jamming part sounds more like thread tension issues, especially if the jamming is happening underneath from the bobbin. If stitching is loose underneath, then top tension is the problem and visa versa.

Recheck your threading path, top and bottom tensions and that you have good quality thread. Change the needle, rewind a fresh bobbin, thread up and try again.

There is really good info on www.sewing.about.com or I refer to my Singer Sewing Machine textbook at lot too. Good luck.

It definitetly sounds like a tension adjustment, make sure the top tension is about 4 or 5 and you should only be able to pull the bobbin thread through with slight resistence, if it is too tight slacken the scew on the bobbin case about a quarter of a turn at a time and test, keep adjusting until you get it right.

on older machines that would be a tension problem. may still have to set the tension on new ones to dont know for sure

Are you using heavy thread for the top stitching? If so you will need to tighten the top tension. You would think if it is thicker thread that you would need to loosen the top tension but you have to tighten it to help pull it up through the fabric. If you use heavy thread in the bobbin you would have to loosen the bobbin tension. Check and make sure the thread is seated in the top tension and make sure there is no lint in the tension disc. It is definitely a tension issue. Hope this helps.