My Dual Sew 3400 catches the bobbin thread, the feed dogs do not seem to be working, the bobbin thread has loops. I have adjusted the tension and cleaned the machine. Suggestions please!

I've found that when FMQing, I usually need to increase the bobbin tension to keep the bobbin thread down (for this reason, I have a separate bobbin case that has the tension adjusted that is used only for FMQ). You may even need to decrease the top tension if the top thread is "pulling" the bobbin thread up.

Sounds like the thread is either coming out too fast or too slow, which means the tension spring needs a slight adjustment. Or perhaps the thread has not been wound smoothly onto the bobbin and has loops. Or the bobbin case is not sitting properly in the holder. Poor thread could also be an answer. Hope one of these work for you

You might try cleaning the tension disks by dampening a length of pearl cotton with rubbing alcohol, open the tension disk all the way, raise the presser foot, and then pull the pearl cotton down between the disks a couple of times.

Clean away the lint and thread pieces from the feed dogs and bobbin area. Oil your machine according to the instruction manual--use only fresh good quality sewing machine oil--only 1 or 2 drops of oil each place.

Install a brand new needle. Make sure you are using a needle and thread that are compatible with the fabric you are sewing--that the thread is not too big for the needle's eye, etc.
All About Needles

Make sure you RAISE the presser foot BEFORE threading the upper thread. Rethread the thread from the beginning checking that thread is not wrapping around the spool pin or catching somewhere in the threading sequence.

Verify that you are threading the machine correctly. Misthreading will cause havoc and frustration!

Do not use old or bargain bin thread--Coats & Clark does create problems for some machines.

You might try pulling the bobbin thread to the top before beginning to sew. This helps prevent some of the thread nests you are experiencing.
How and Why to Bring up the Bobbin Thread

The factory tension setting is usually the halfway point between the high and low number. This is where you should start testing your tension. Once you sew a sample, if the top thread is looping/knotting (bird nesting) under the fabric, the upper tension is most likely too loose. If the bobbin thread is pulling to the top of the fabric, the upper tension is too tight. Get used to adjusting the upper tension every time you change fabric, needle, thread. The upper tension is not meant to be static, so don't be afraid to adjust to achieve the proper tension.

Ideal tension is when both the upper thread and bobbin thread meet in the middle of the fabric.

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1. Make sure to adjust the bobbin tension. Also, make sure the bobbin is correct for the machine. If it is too tall it will surely have problems. (see attachment for bobbin tension adjustment)
2 Always thread your machine with the pressure foot up. As you thread give gentle tugs to check for hang ups. This has to be corrected.
3. Adjust the top tension to four to begin with. Final tension adjustment can be made when you give a trial sew.
*Always oil race w/one drop of oil before the bobbin case is placed back. This is done only about every 10000 stitches.

Hi Sylvia,
Your problem is an un-matched tension of the threads. You mentioned doing an adjustment recently. That is the problem area.
If your bobbin thread develops loops on the top side of the fabric, you need to tighten the bobbin tension.
There is no easy method for this and you will have to do it slowly -
tighten, test, re-tighten, test.... until you get a near perfect stitch.
I haven't come across a portable device specifically designed to set thread tensions.

OK, Nylon thread and vinyl fabric are difficult. Try this:
1. Be sure your machine is *very* clean - no leftovers from previous projects.
2. Take the bobbin receiver out (need a screwdriver to hold the release), clean it and all around it and re-insert. When you re-insert in this machine, hold the release lever with the screwdriver, push the receiver away from you (under the feed dogs) then bring it back toward you so it catches before you release the catch.
3. Use a stitch length just a bit longer than you 'normally' would - 3+ for vinyl.
4. Wind your nylon thread onto a bobbin *very* carefully. It's easy to get it caught so that it won't feed evenly.
5. Be sure your upper thread is in properly, and that it doesn't catch on anything.
6. Adjust your upper tension tighter than 'normal' to accomodate the slippery thread your're using - do this a little at a time, it's easy to miss the 'sweet spot' if you adjust too much.
7. Be sure to bring up your bobbin thread and hold both threads as you start to sew - hold them for 3-4 stitches.
8. Sew slow - this machine can go *really* fast, but don't let it on this project. It will catch better if you take it slow and easy.

Hope all this helps. If not, you'd probably better take it in for service.

Check the tension of the feed foot. Some machines have an adjustable tension for the foot pressure. If this is not the case then re-check your thread tension setting. As well clean the bobbin area of loose threads and dirt. You can adjust the bobbin thread tension on the side of the bobbin holder(small screw). From the sounds of your dilemna the bobbin tension may be the culprit. The housing does come out with either 2 screws, or clips. Try that. Wayne

If the machine is now threaded, lift the presser foot.

Now, pull about 10" of thread through the needle.

The next time you thread the machine, lift the presser foot first.

When the presser foot is up, the tension control opens and allows the thread to "seat" into the control, then when the foot is down the control closes to the indicated setting.

When threading the machine with the foot is down, thread does not enter the tension control and when you start to sew, there is no tension on the thread.

No tension = loosey, goosey, loopy stitches underneath.

Because the lack of tension on the top thread, the bobbin thread cannot lock a proper stitch.

When the sewing machine is properly timed, all the parts work together in a seamless flow of coordination. The needle moves from it highest point down toward the needle plate. The feed dogs reach the farthest point toward the back of the sewing machine. The feed dogs drop under the needle plate. This is just before the needle point reaches the needle plate. The needle continues to move down dragging the upper thread under the needle plate. It proceeds toward its lowest point.
The needle begins its rise back up. A loop of thread forms along the back of the needle. A special cut out on the back of the needle to accommodate this loop is called the scarf. The sewing machine hook slides behind the needle. The point of the hook slides into the thread loop and pulls the thread around the bobbin. The bobbin thread and upper thread wrap together. The needle and hook proceed through their actions under the needle plate. The feed dogs move under the needle plate from back to front.

The needle proceeds to rise again up out of the bobbin area exiting the needle plate. At the same time the feed dogs rise up out from under the needle plate. They begin to move from front to back as the needle continues to rise.
The thread from the bobbin flows through a bobbin tensioner providing resistance to the thread as it is drawn up by the upper thread knot. The upper thread is also under tension. This comes from the upper tension, thread guides, tension spring, and sewing machine take up lever.
The thread from top and bobbin grow increasingly tighter until they form a locked stitch in the middle of the fabric. This process is repeated for every stitch.
How do you adjust sewing machine timing?

The needle, hook, and feed dogs must move in harmony. If they fail to do so, the machine will not perform as expected. When the hook is just slightly out of time with the needle, you will notice skipped stitches. This may begin on only one side of the zig zag stitch or intermittently. If the timing is just a bit more out of sync, stitch formation will become impossible.
If the feed dog timing is out of sync, the fabric will not move through the machine as expected. Threads may bunch up or the fabric may just not move.
As you can see, timing is everything.
click on this link directly
http://www.fixsewingmachines.com/How-to-Adjust-Sewing-Machine-Timing.html

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Proper set of bobbins and tension set up vs. fabrics will sew you satified.Also incude regular maintenance cleaning of the feeds dogs with a brus,also the shuttle assembly need sometime to clean.Some threads and fabrics chips accumulates in the feed dogs and shuttles assembly.In setting up thread bobbins the thread should be clockwise direction as you pull out on slot coming out to the bobbins (as you shown in my inserted image manual).The loop thread should be propely in the sequence position same like in the image refer to it.If you use cotton/ polyester fabric in the begining of trial set tension dial to No.3 and stich to No. 8 to 12 any convenient to you Use needle No. 14 .Posible make a record if you are sewing different types of fabric mostly silk fabric is hard to sew adjusting to lower stich can posible sew satisfactory.