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Thread Tensions – All Machines
2. Bobbin Case Tension
!" What is it for?
To keep under thread tension constant, works with top thread to form a proper stitch.
!" When do you check it?
At install and at every bobbin change. When tensions are believed to be the problem,
ALWAYS check and adjust bobbin first if necessary. The bobbin tension will change
over time due to lint build up underneath its tension spring.
When do you clean it?
Clean the bobbin case when you can no longer get enough tension on the bobbin. For
example, when the adjustment screw is turned all the way down or the bobbin tension
becomes erratic.
How do you clean it?
Loosen the adjustment screw until the spring
lifts off the bobbin case about 1mm. You
may want to do this over a table just in case
you loosen the screw too much and it falls
out. It will make it easier to find. Then using
the corner of a piece of backing, rub
underneath the spring to remove any lint
buildup. Then adjust by retightening the
screw and recheck your tension.
!" How do you adjust it?
One of the most accurate ways to check the
bobbin tension is with a bobbin tension
gauge. The guage will take into account the
pressure of the anti-spin spring while setting
the tension. Adjust the bobbin tension after
adjusting the anti-spin spring and cleaning
under the bobbin tension spring on the
bobbin case. You will not need a full bobbin
to check the tension when using the gauge.
When inserting the bobbin into the bobbin case it should spin
clockwise when viewed from the backside. Insert the bobbin into the
gauge and adjust the tension between 15-30 grams with 22 grams
being ideal. Read the tension of the gauge while pulling the bobbin
thread slowly out away from the gauge. Do not pull to fast or to slow
as these are not realistic speeds of the bobbin. It is important to pull
the thread smooth and steady to get a good reading. If you see the
needle on the gauge jumping up and down, there could be a problem
with the sides of the bobbin itself. The cardboard could be bent over
or the bobbin could have been wound incorrectly. If you see the
needle on the gauge jumping up and down, the machine will have erratic tensions looking
tensions of the backside of the garment as well. Discard or fix that bobbin if possible.
You will want the bobbin thread to come off bobbin as smoothly as possible.
Checking without a bobbin tension gauge. First clean under the tension spring on the
bobbin case, and then insert a new bobbin. Hold the end of the bobbin thread up and find
the point at which the tension spring will hold the weight of the new bobbin and the case.
Adjust the tension spring to let the bobbin and case start sliding down the thread by it's
own weight. This method is not meant to replace the use of a gauge, but to get you close
to proper tensions if you do not have one. You may need to further tighten the adjustment
screw if the bobbin thread is showing on the topside of the fabric while sewing.
For Technical Assistance Please Call Toll Free 1-877-4BROTHER
2
Part # BTG3
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