Tracking Down the Problem Part 5 Thread Tensions
Overall Theory:
In reality there are three
tensions to deal with in embroidery. The bobbin tension, top tension and the fabric
tension. Check your hooping before you begin adjusting thread tensions.
Checking the threading of the bobbin case and upper
thread.
The thread should pull out smoothly.
Check the bobbin both in and out of the machine. Overwound
bobbins may not be noticeable until the bobbin is inserted in the machine.
Look for damage to the bobbin, bobbincase or thread cone.
Make sure the upper thread is in the pretensioner and
tension.
Begin all adjustments at the bobbincase.
Utilizing a bobbin tension gauge you should have 18 - 20
grams.
Do the drop test. Put a fresh bobbin in the bobbincase,
thread the bobbincase correctly except for the "pigtail". Hold the bobbincase up
by the thread (leave a hand underneath so it doesn't hit the floor!), let it dangle and
jerk the thread to test the tension. If the bobbincase drops a few inches and stops you
are in the ballpark. If it doesn't drop at all it's too tight. If it hits the floor it's
too loose and you forgot to put your other hand under it.
Start top thread adjustments at the pretensioner.
Utilizing a tension gauge, approximately 10 grams.
Without a tension gauge loosen the main tension knob out
so it is not putting any pressure on the tension spring. Remove the thread from the eye of
the needle, thread it through the hole in the presser foot. Place your finger on the main
tension disc to prevent it from turning. Pull off thread. If the thread stops pulling
around the main tension disc the pretensioner is working. If not, tighten the pretensioner
until the thread flow stops (continue holding the main tension disc so it doesn't turn
while you adjust). If the main tension disc doesn't turn when you are NOT holding it you
have too much tension on the pretensioner. If the thread repeatedly slips off the main
tension disc you have too little pretension.
Main tension adjustment.
Utilizing a tension gauge, measure the tension
just after the main tension, approximately 20 grams.
Without a tension gauge back the tension knob all the way
off. Turn the knob in 6 - 8 full turns. Sew a 2 inch block I, preferably without serifs.
You should see two thirds of the upper thread pulled to the back of the I with one third
bobbin thread running down the center of the I. If you are showing more upper thread on
the back tighten the main tension. If you are showing more bobbin thread on the back
loosen the main tension. Sew again.
Double check your adjustments by sewing a block H or X on
all needles. Once the bobbincase tension is set do not readjust it for individual needles,
adjust only the top tension.
Check the front for looping or pulling.
For narrow satin stitches (columns of 3mm or less) you may
want to run a little tighter bobbin tension, showing less than 1/3 on the back.
Note: These settings have
been tried and tested on Tajima Embroidery Machines.
For more information on tension
gauges, click here.
