Sewing a straight seam will be going well until the bottom thread suddenly becomes very loose and loopy. The top thread is completely fine. The only clue that this is happening is the spool "jumping" instead of unwinding silently and consistently. I suspect a bobbin problem...I rewound the bobbin, but it happened again resulting in more seams needing to be ripped out. Any ideas about what is happening with my bobbin?
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Re: Bottom (bobbin) thread suddenly loosens
A few steps to help you troubleshoot:
Bobbin in the right direction: when looking at the bobbin in the bobbin case, pull the thread tail. The bobbin should turn clockwise.
One of the biggest causes of what you describe is simply a burr/rough spot on the needleplate or hook.
Remove the needleplate from your machine and inspect the opening for any rough spots... run your finger over the area to feel for any sharp bits. If you discover some rough spots, they can be smoothed using a fine emery cloth. Use this gently - don't want to distort needle opening, just smooth the roughness.
If no rough spots on needleplate, open the bobbin cover and turn the handwheel towards you until the hook (little pointy part of bobbin area) is towards the bottom of the machine. Run your finger over the point to feel for any rough spots. Again - a fine emery cloth can smooth this. Be VERY careful to not flatten the hook - just a little smoothing to get rid of rough bits. Too much can ruin the hook. If you're uncomfortable with this, don't hesitate to take to your Pfaff tech and point out the rough bits.
Hold the bobbin case/bobbin between finger/thumb, making sure you're not pressing on the bobbin tension (little flat metal piece on side of case). Pull the thread smoothly out of the bobbin case to see if you feel any little glitches. If you do, there may be a bit of fuzz/broken thread trapped under the bobbin tension.
You can loosen the large setscrew on the side of the case to allow you to blow out whatever may be trapped.
While your top thread may appear fine, there may be a bit of fuzz or broken thread wrapped around the take-up lever. This would interfere with the smooth feeding of the upper thread, also causing an inconsistency in the bobbin.
Use a flashlight and look down into the top of the machine/takeup lever area. You may be able to see a bit of thread and remove it. If you can't see an offending bit, try "Flossing" your upper thread path by grasping the thread close to the spool and after it comes out of the needle. Run the thread back and forth through the thread path to see if you can dislodge anything
If none of the above help, we'd suggest you have your local Pfaff authorized tech take a look. It's always a good idea to take your machine to it's respective authorized service person as they'll be the ones to know the most about it and have access to any repair parts.
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You can use either 16 or 16J. If your threads are loopy on the bottom side of fabric, the problem is either your needle thread tension is too loose or you have a snag in your needle plate where you have broken a needle. Check needle plate and clear snag if any. Then tighten up your needle thread tension until both needle and bobbin threads are in middle of fabric.
Your description isn't very clear. When you say the "bottom stitch is using too much thread" Do you mean you see lots of loopy threads on top of the seam? Or do you mean you see loops on the bottom under the fabric? If your loops on the bottom, that means the top tension is too loose, you've not remembered to put the presser foot down, you have not threaded the top thread properly... Start by rethreading carefully with the presser foot UP. Then do a test stitch, remembering to put the presser foot down. If you still get loops underneath... tighten the tension.
If your loops are on the top of the fabric. loosen the top tension... then do a test seam... and if you still have loops loosen again and repeat. If you start to see loops on the bottom... tighten the tension a bit.
Make sure bobbin is loaded correctly and unwinding in the correct direction. It does make a difference. Do a test seam. If not improvement....
Loosen top tension. Do a test seam to see if that helps. If it does, loosen some more until you have a balanced stitch.
Finally... if neither of those really help. Look on the bobbin case for the tension "spring" (it is flat) with two tiny screws. One holds it on... the other tightens or loosens tension. Tighten the tension on 1/4 turn. Do a test seam. Etc., etc., etc.
The only time one ever changes the bobbin tension is when they are either using substantially larger or substantially thinner thread.
If by "bobbin thread is usually too loose." you mean that you are seeing loopy stuff on top of your seam... then first you need to make sure your bobbin is un-spooling in the correct direction.
Also make sure that the tension spring on your bobbin case is not missing it's screw. Don't mess with the tension there yet... loosen your top tension first... sew on scrap fabric of the same type as your project. Loosen the top tension until you stop seeing loops on top of your seam. If you have loosened it enough to see loops on the bottom... tighten it a bit.
If all else fails make sure you re-thread the top thread with the pressure foot up position so you make sure you are getting the top thread in the tension discs and try test sewing again.
Load your sewing machine with one color on top, threaded through the needle. Load the second color thread into the bobbin and thread.
Fold the scrap fabric in half, and sew a straight stitch at least 2 inches long. Look closely at the seam. If you see loops of the bottom color thread on top of the fabric, proceed to Step 3. If you see loops of the top color thread on the bottom of the fabric, proceed to step 4.
Loosen the top tension. Since the top tension is so tight, it is pulling the bottom thread up through the fabric. Loosen the top tension by turning the numbered knob on the front of the sewing machine counterclockwise by one number.
Tighten the top tension. Since the top tension is too loose, the bottom thread is pulling the top thread down through the fabric. Tighten the top tension by turning the numbered knob on the front of the sewing machine clockwise by one number.
Sew a straight stitch 3 inches in length. Check the stitching. It is perfect if the threads meet in the middle, and you can only see the top thread on top and the bottom thread on bottom. If it still needs adjusting, go back to step 2 to repeat the needed steps.
Using two different colored threads makes it easier for you to see which thread is being pulled.
Always use proper precautions when working with electrical machines.
The bottom stitch is affected by the TOP thread tension :) First go back and make sure your bobbin tension is correct since you adjusted it. It should drop slightly when held suspended by danging it by the thread. If it reels out to the floor it is too loose. If it doesn't drop at all it is too tight.
Now that you have that adjusted look at your top tension. If it is loopy on the bottom side of the stitch the TOP tension is too loose. Increase the top tension.
Now take some scrap material and set machine to a wide zig zag, medium length stitch and sew a bit. Compare the top and the bottom sides of the stitch. They should look identical. Remember the TOP side effects the bottom and the BOTTOM tension effects the top side. Adjust accordingly until they look identical with no loose threads or loops and no puckering (puckering means it's too tight).
Hi! Sounds like you're doing everything right to me, so let's see.
By not getting a straight stitch on the bottom, do you mean that the bobbin thread is loopy? If so, then most likely you have to reset the tension. Get a scrap of jeans material and practice on that....it would be great if you could use different color threads on top and in the bobbin, but that might not be practical if you don't have the jeans thread in different colors already.
You'll be adjusting the top tension, because even tho the top stitch looks perfect, it may not be tight enough to pull the bobbin thread up into the fabric where it belongs.
Sew a couple of inches on your scrap, then stop and check the bobbin thread. If it's loopy, you can also see the top thread on the underside. (Which is why using two colors is helpful.) With the pressure foot down, tightened the top tension just a bit. Sew a few more inches and check again. Keep on sewing, checking, and adjusting until you can't see any (or almost any) top threads on the bottom or bobbin threads on top.
Here are a couple of other ideas to check:
1. Make sure your bobbin is inserted correctly. If I happen to put one in backwards by mistake, the bobbin will make a lot of clanking noises.
2. Using your flywheel, lower the needle all the way through the stitch-making process to see if it's hitting anything along the way.
3. Oil your machine.
4. Make sure all the screws etc on your throat plate (also called needle plate) are tight. (I've had mine get loose and that will definitely throw a knock into the works!)
Check out these ideas and let me know if anything works, or if the problem is still there, ok?
The case that holds the bobbin in the bottom has a small screw that needs to be tightened. Do so by a quarter turn at a time and test the sewing on a scrap of the same material you are working on until you get an even tightness between top and bottom threads.