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  1. #1
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    Thread tension help

    Hey everyone, I have a Kenmore sewing machine (385.12714090) that was passed to me from my grandmother. I used it to make some gear a few years ago, life got busy, and I just pulled it from the basement. It ran OK, but the thread tension was off and the stitch selector wasn't producing the correct stitches. I can't afford a service for it right now, so I opened it up. I was able to fix the stitch selector, which now works perfectly. Put a tiny bit of light oil everywhere the manual said to, blew out the fuzz and threads, and put it back together.

    I did find a small, bent spring lying inside the case. I couldn't find where it was missing from. I don't think the engineers typically put in extra destroyed springs for fun, so.. I'm guessing something was damaged when I broke a needle trying to sew webbing straps a couple of years ago. I have not found what the spring went to, and I can't see any operational problems other than the issues I describe here.

    Now everything runs smoothly, but I am having tension issues.

    The problem: When the bobbin tension is set at a good starting point based on what I've read here and elsewhere (tick-tock motion of the bobbin case held by thread makes it move a little with every swing) and the top tension is set to mid range (4 on a 0-9 scale), I get massive loops/bird nesting on the bottom. When top tension is maxed, I still get loops on the bottom but they don't tangle.

    As the bobbin tension is decreased, the problem decreases slightly. However, when bobbin tension is decreased completely (IE the screw is about to fall out) and top tension is maxed out, I still get symptoms of too-tight bobbin tension and too loose top tension - knot shows on the bottom of fabric, and the bottom thread is loose and just lays on the fabric on the bottom.

    What I've done to troubleshoot:

    -Rethreaded the machine 1000 times
    -Changed thread both top and bottom (was using gutterman polyester, ran out, now using a cotton thread for testing purposes only)
    -Carefully made sure the bobbin was loaded properly
    -Checked top tension discs to make sure they're reinstalled correctly - when I put the top thread in and set it to 0, it takes much less force to pull the thread out than when I set the top tension to 9, so I know that the top tension discs are engaging the thread and the adjuster is producing a range of tension.
    -Checked for burrs, dislodged or improperly installed parts around the bobbin case and surrounding area.
    -Changed to brand new needles
    -When I get a new spool of Gutterman thread, I will wind a brand new bobbin and try again (probably tomorrow)
    -Using kenmore bobbins that came with the machine as well as third-party generic bobbins
    -Problem occurs when using the motor and when turning manually
    -all lines of stitches start with 3-4, then back to lock them in, then forwards.
    -using straight stitch, setting of 2-3 for stitch length.

    Manual/parts/model number here: http://www.searspartsdirect.com/part...d=&documentId=



    So, for those of you experienced in troubleshooting sewing machines, what else would you check here? Are there any other problems that would present with symptoms of bobbin tension that is too high?
    Last edited by booone0; 01-19-2015 at 07:44.

  2. #2
    Senior Member Bubba's Avatar
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    Did you clean the feed dogs?
    Don't let life get in the way of living.

  3. #3
    Member Hammockmadness's Avatar
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    Do you get the same results with other types of thread? Could be the weight of thread that you are using.

  4. #4
    Senior Member Ramblinrev's Avatar
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    Reset the bobbin tension and leave it alone. Adjusting the bobbin tension in the vast majority of cases will not solve tension problems. There are several issues involving the top tension that you need to look at. What does that spring you found look like. A pic would help. The tension discs should be spring loaded. When the presser foot is up there should be no tension at all on the top thread. So set the top tension to max... raise the presser foot and test then tension by pulling the thread as you have done. If the thread pulls freely the tension plates are likely assembled correctly. It is not unusual for the tension springs to wear out or break. IME the tension springs are flatish coils that are higher in the middle than the edges. If your spare spring looks like that you can narrow it down pretty quickly. Replacements should be available at a reasonable cost.
    I may be slow... But I sure am gimpy.

    "Bless you child, when you set out to thread a needle don't hold the thread still and fetch the needle up to it; hold the needle still and poke the thread at it; that's the way a woman most always does, but a man always does t'other way."
    Mrs. Loftus to Huck Finn

    We Don't Sew... We Make Gear! video series

    Important thread injector guidelines especially for Newbies

    Bobbin Tension - A Personal Viewpoint

  5. #5
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    Bubba - blew the feed dogs out with compressed air. When I get home, I'll remove the plate and make sure there's nothing stuck there. I didn't give that area as much attention so it's possible there is something stuck, but unlikely. The feed dogs do move and seem to pull fabric through at a correct rate.

    Madness - same result with gutterman, a random polyester thread (thinner than the tera), and a generic multipurpose cotton thread of unknown weight/quality. Switching to new gutterman thread as soon as I get it from Dutch, probably tomorrow.

    Ramblinrev - First, I know now not to mess with bobbin tension... I did not know that a couple years ago and messed with it, so to start, it was probably incorrect and I knew it was a variable that had to be dealt with. When I load it up again with new thread, I'll set the bobbin tension according to your instructions and keep it.

    Top tension - I closely examined the top tension assembly. Raising the presser foot does remove top thread tension. Lowering it again restores tension on the top thread. When set to 9, the top thread tension is noticeably greater than when it is set at 0. The tension spring appears to be in good shape, applies force to the discs, and does not appear deformed. There is no place on the top tension unit that I can see where the "extra spring" would attach.

    As far as the extra spring: it was found in the upper case. It looks like it was originally shaped like this:

    http://en.wikipedia.org/wiki/Spring_...prings_009.jpg

    I would estimate the dimensions of the coil at about 3mm diameter by about 5-8mm length, about the same gauge wire as the spring you'd find in a pen. I'm at work so I can't get a picture of it right now, but will when I get home.


    One more detail to complicate things: I believe the needle/shuttle timing or needle bar height may be slightly off. I can see jamming it up enough to break a needle, as I did in the past, being enough to mess this up. The needle shaft just barely rubs on the shuttle. Could that cause the symptoms I am having?

    I appreciate everyone taking the time to help my troubleshoot the machine!

  6. #6
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    Quote Originally Posted by booone0 View Post
    -Checked top tension discs to make sure they're reinstalled correctly - when I put the top thread in and set it to 0, it takes much less force to pull the thread out than when I set the top tension to 9, so I know that the top tension discs are engaging the thread and the adjuster is producing a range of tension.
    It sounds like you've had the upper tensioner taken apart. Just because it produces a "range of tension" doesn't mean it is producing the correct range of tension.

    Check to make sure there is not any balls of lint or bits of thread between the tension disks and then see the 'Top Tension' section for how to adjust the range higher....http://www.managemylife.com/mmh/lis_...M/L0612394.pdf

  7. #7
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    Quote Originally Posted by gmcttr View Post
    It sounds like you've had the upper tensioner taken apart. Just because it produces a "range of tension" doesn't mean it is producing the correct range of tension.

    Check to make sure there is not any balls of lint or bits of thread between the tension disks and then see the 'Top Tension' section for how to adjust the range higher....http://www.managemylife.com/mmh/lis_...M/L0612394.pdf
    I removed the whole unit because I (mistakenly) thought that was necessary to get the front cover off. So no adjustment was made to the tension spring, as it all comes off in one piece. The only thing to check was that the lever that releases tension when the presser foot is up was properly engaging the tension unit... It is. Either way, I will take a look at the link you posted.

    Part of my cleaning involved the top tension discs, they are totally clear.

    Thanks!

  8. #8
    Senior Member Ramblinrev's Avatar
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    Definitely not a tension spring. I don't know what it might be. Of course there is always the possibility that some one lost the spring from a pen and it fell down inside the machine. Stranger things have happened.

    Before you do anything else you will have to make sure the timing is adjusted properly. I'm not a repair mechanic so I can't be of much help in that regard. But I will say timing messed up enough to break a needle is really going to muck things up. No point trying to tweak anything more until that gets fixed.
    I may be slow... But I sure am gimpy.

    "Bless you child, when you set out to thread a needle don't hold the thread still and fetch the needle up to it; hold the needle still and poke the thread at it; that's the way a woman most always does, but a man always does t'other way."
    Mrs. Loftus to Huck Finn

    We Don't Sew... We Make Gear! video series

    Important thread injector guidelines especially for Newbies

    Bobbin Tension - A Personal Viewpoint

  9. #9
    Senior Member Scotty Von Porkchop's Avatar
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    Quote Originally Posted by gmcttr View Post
    It sounds like you've had the upper tensioner taken apart. Just because it produces a "range of tension" doesn't mean it is producing the correct range of tension.

    Check to make sure there is not any balls of lint or bits of thread between the tension disks and then see the 'Top Tension' section for how to adjust the range higher....http://www.managemylife.com/mmh/lis_...M/L0612394.pdf
    I agree with gmcttr that this is probably the most likely issue, I did the same thing on a refurbishment. Also check if there's any roughness or corrosion to the thread tension plates, I also had this and it can cause problems, most usually inconsistent tension.

  10. #10
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    Cool everyone, thanks for the direction! I'll check on all of this when I have a minute and let you know what happened.

    Rev - just to be clear, the needle broke trying to sew webbing straps too fast, causing a birds nest and broken needle. I only found the timing off because I saw the needle brushing up against the shuttle when cleaning it yesterday.

    Scotty - checked tension discs, no corrosion and cleaned with alcohol in case there was any gunk, then checked to make sure there was no lint.

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