Bobbin thread is straight adjusting upper tension does nothing

Your upper and lower thread tensions are out of balance. The upper thread tension is too high or your lower thread tension is too low. Make sure your bobbin thread is correctly routed under the tension spring. There is a small screw on the bobbin case that always you to adjust tension.

Tension is a common problem for new and even intermediate sewists. Testing is about the best way to figure out what works for your machine.

Be sure you are using a brand new needle and that it is installed correctly (flat side facing the proper direction).

ALWAYS RAISE the presser foot when threading the upper thread. This releases the tension disk so the thread will seat completely. Check the thread path and verify that it is correct. Missing one thread guide will create havoc!

Check that the bobbin thread is wound smoothly and that there are no thread ends sticking out of the bobbin anywhere. The bobbin must turn in a specific direction when in the bobbin case and the bobbin tension needs to be threaded correctly. (For this, you need to consult your owner's manual.)

Set the upper tension to the mid-way point. This is the default setting although it will most likely require some tweaking because all machines are just a bit different. Tweaking is a very common necessity as different threads and fabrics will affect the tension.

Set the straight stitch length to somewhere around 10 stitches per inch.

Use two pieces of medium weight fabric, like 100% cotton. Bring the bobbin thread to the top of the fabric before beginning to stitch.

https://www.youtube.com/watch?v=KDERq4I7l-Q


http://ohyoucraftygal.blogspot.com/2013/10/sewing-lesson-10-how-to-fix-tension-on.html

Understanding Thread Tension Threads

Test your stitch. The ideal tension is when both the top thread and bobbin thread meet in the middle of the fabric.

If the top thread is looping or showing under the fabric and the bobbin thread appears to be running in a straight line, the top tension is too loose.

If the bobbin thread is showing on the top of the fabric or the upper thread is running in a straight line, the upper tension is too tight.

Keep adjusting until it looks like the pictures in the web links above. Remember, when you change thread or fabric weights/types, etc., you will probably need to re-test the tension and adjust.

One more suggestion: use good quality thread. AVOID old or bargain bin threads. They may save you money but will cost a lot in frustration.

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First, make sure the upper tension is too tight. Tight upper tension will pull the bobbin thread up to the top of the fabric.

Bobbin Tension How and Why Tension is Adjusted

Understanding Bobbin Tension

How can properly adjust my tension

Understanding Thread Tension Threads

Oh You Crafty Gal Sewing Lesson 10 How to Fix Tension on Your Sewing...

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Usually, if there are loose threads under the fabric, it is the top thread that is too loose. Check your sewing sample closely--you can even test with two different color threads to help distinguish which thread is which. Loose top thread will generally be pulled DOWN and show under the fabric. Loose bobbin thread will be pulled UP and show on the top of the fabric. The ideal tension is when both threads MEET in the middle of the fabric.

First, remove the thread from the machine. Install a brand new needle. Always Raise the Presser Foot and thread the upper thread, making certain the thread path is correct.

Check that the bobbin thread is threaded correctly and turning the proper direction in the bobbin case.

Set the upper tension to the midway point and sew a retest. A tweaking of upper tension may be necessary to get it where it should be. Generally, upper tension should make the majority of adjustments needed for tension correction. Bobbin tension is one of the last tension adjustments to make as it is very sensitive and can go awry very quickly.

If, in fact, the bobbin tension is off, the tension skrew on the bobbin case is where the adjustment is made. Before making any bobbin tension adjustments, mark where the skrew slot is located on the bobbin case with a permanent marker. This will allow you to reverse your changes if necessary. Be CAREFUL as TINY changes make HUGE differences in tension. Make only 1/8th turn adjustment, then retest before making another adjustment.

Remember that tension testing and readjustment are a necessity when sewing. The same tension that will work with light weight thread and fine fabric will most likely not work when using heavy thread on drapery fabric. Get comfortable with making tension adjustments to get the ideal tension for each project.

Understanding Thread Tension Threads

Oh You Crafty Gal Sewing Lesson 10 How to Fix Tension on Your Sewing...

https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=14&ved=0ahUKEwilg-3t2vHMAhVJDlIKHXnsBWYQFgheMA0&url=http%3A%2F%2Fwww.ca.uky.edu%2FHES%2Ffcs%2FFACTSHTS%2FCT-MMB-213.pdf&usg=AFQjCNE4QlGk1Fvt8K2UGCRCfzMpGS-A2Q&cad=rja

How to Adjust the Tension on Sewing Machine

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top tension too loose
tighten it up

First, be sure you are using a brand-new needle and that the needle, thread, and fabric are compatible.
All About Needles

When you thread the upper thread, be sure the presser foot is ALWAYS RAISED so the thread will seat properly in the tension disk. Also, confirm that the machine thread pathway is correct.

Remember that when fabric types/weights are changed, the needle/thread should be changed accordingly. (Needles should be changed often to attain the best sewing experience and minimize unnecessary frustration.) The tension may also need to adjusted. Tension is not static. It should be adjusted to fit the project being sewn. Unless one continuously sews with the same fabric, thread, and needle type would the tension adjustment remain at the same setting, but machines do change over time so a tension setting that worked last year may not look the same this year.

The factory standard tension setting is the midway point between the high & low numbers. However, please understand that machines vary and that sometimes this standard setting may change with time and use. The midway point should only be the beginning point and is most likely suitable for medium-weight fabric. Also, usually the bobbin tension does not require frequent adjustments unless a particularly heavy- or light-weight thread is used in the bobbin--sometimes the bobbin tension will get out of whack requiring adjustment (consult the owner's manual or search the internet for instructions for adjusting bobbin tension). In the majority of cases, the tension adjustment is made to the top thread.

Test your straight stitch on your fabric (may be helpful to use a different color thread in the bobbin so it is easier to see any tension issues). If the bobbin thread is popping up to the top of the fabric, loosen the upper thread tension. If the upper thread is looping or showing on the bottom of the fabric, tighten the upper tension. Keep adjusting until the upper and bobbin threads meet in the middle of the fabric.

FWIW, the same process would be used for zig-zag stitching. Just make sure that the tension is not too tight or it will cause the fabric to pucker (or tunnel).

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Generally, tension adjustments are made using the upper thread tension. Most likely the upper tension is set too tight and is pulling the bobbin thread up. Loosen the upper tension and try again. Tension is accurate when the upper thread and bobbin thread meet in the middle of the fabric. Whenever fabric, thread & needle are changed, there may be a need to adjust the upper tension.

HINT: When threading the upper thread, make sure the presser foot is RAISED during threading to make sure the upper tension disks are open and the thread seats properly.

Bobbin tension is only adjusted when the tensions are way out of whack. Only slight turns of the bobbin case tension screw are made in graduated movements and testing occurs after each adjustment.

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Is your bobbin threaded correctly? You should be able to pull out the thread slowly while feeling it very slightly holding back. It should not pull out easily or quickly.
Could be something wrong with your tensions, try adjusting the upper tension first by starting at the middle setting and working gradually higher and then lower till you get a neat even stitch.

Is it really the bobbin thread that is bunching under the fabric, or is it really the top thread that is creating loops and "bird nests" under the fabric???

Rethread your upper thread. BEFORE you thread the upper thread, be sure to RAISE the presser foot. This releases the upper thread tension disks so the thread is firmly seated in the tension disk.

If it continues to be a problem, then the upper tension needs to be tightened. Adjust slightly, then test. Repeat until the upper and lower threads meet in the middle of the fabric.

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According to the manual, you should not need to adjust the bobbin tension (and I located other sites which stated the bobbin tension cannot be adjusted on this machine). Apparently, all the tension adjustment is accomplished through the upper thread::
"EN Thread Tension Upper thread tension Basic thread tension setting: "4". (1) To increase the tension, turn the dial to the next number up. To reduce the tension, turn the dial to the next number down. A. Normal thread tension for straight stitch sewing. B. Thread tension too loose for straight stitch sewing. Turn dial to higher number. C. Thread tension too tight for straight stitch sewing. Turn dial to lower number. D. Normal thread tension for zig zag and decorative sewing. Correct thread tension is when a small amount of the upper thread appears on the bottom side of fabric. Lower thread tension The bobbin tension has been set correctly at the factory, so you do not need to adjust it. Please note: - Proper tension setting is important for strong seams. - There is no single tension setting appropriate for all stitch functions, thread or fabric. - A balanced tension (identical stitches both top and bottom) is usually only desirable for straight stitch construction sewing. - 90% of all sewing will be between "3" and "5". - For zig zag and decorative sewing stitch functions, thread tension should generally be less than for straight stitch sewing. - For all decorative sewing you will always obtain a nicer stitch and less fabric puckering when the upper thread appears on the bottom side of your fabric. 1 A B C 22 D"

Doing further research, I found this statement on a machine review site:
"After reading reviews online from where I've bought my drop-in bobbin machines, I think many of the negative reviews are due to the bobbin thread coming up without laying across the bobbin. It can cause the stitches to look very sloppy and no amount of tension adjusting can fix the stitches."

There are several machine review sites wherein 4423 owners stated their disappointment in the 4423's performance. Some said the machine failed almost immediately and others said the machines developed problems when sewing heavy fabric.