JUKI MO-6800S Series Engineer's Manual page 37

Adjustment procedures
1) Replace the upper knife
1. Loosen the screw ❶ and move the lower knife holder ❷ to the
left. Then, tighten the screw ❶ a little.
2. Remove the screw ❸ and replace the upper knife ❺ with a new
one. Then, tighten the screw ❸ a little.
3. Turn the pulley to move the upper knife ❺ to the lower dead
point. Adjust the height of the upper knife ❺ so that the upper
knife ❺ can cross the lower knife ❻ about 0.5 to 1.0 mm. After
the adjustment, tighten the screw ❸ .
4. Loosen the screw ❶ and return the lower knife holder ❷ to its
original position. Test if the upper knife ❺ and the lower knife ❻
can cut the thread exactly, and then tighten the screw ❶ .
2) Replace the lower knife
1. Loosen the screw ❶ and move the lower knife holder ❷ to the
left. Then, tighten the screw ❶ a little.
2. Loosen the screw ❹ . Take off the lower knife ❻ and replace a
new one.
3. Adjust the blade section of the lower knife ❻ to be aligned with
the top surface of the throat plate ❼ . After the adjustment, tight-
en the screw ❹ .
4. Loosen the screw ❶ and return the lower knife holder ❷ to its
original position. Test if the upper knife ❺ and the lower knife ❻
can cut the thread exactly, and then tighten the screw ❶ .
3) Adjusting the overedging width
1. Turn the pulley to move the upper knife ❺ to the lower dead
point.
2. Loosen the screw ❶ and move the lower knife holder ❷ to the
left. Then, tighten the screw ❶ a little.
3. Loosen the screw ❽ , and move the upper knife holder ❾ left or
right till reaching the desired width. Then, tighten the screw ❸ .
4. Loosen screw ❶ . Move the lower knife holder ❷ until the lower
knife ❻ comes in contact with the upper knife ❺ .
Test if the upper knife ❺ and the lower knife ❻ can cut the
thread, and then tighten the screw ❶ .
4) Resharpening of the knife
1. When the knives have become dull, fully resharpen lower knife ❻
until the contact mark of it disappears.
2. When the upper knife ❺ has become dull, replace it with a new
one. (This is because the upper knife is a serrated carbide knife.)
Results of Improper adjustment
The lower knife ❻ , if positioned
o
too high, will catch materials or
cause no contact of the press-
er foot with the throat plate top
surface.
If the lower knife ❻ is positioned
o
too low, the cutting width will
be changed or materials will be
caught by the lower knife.
The upper knife ❺ , if positioned
o
too high, will fail to cut materials.
Unsharp cutting or abnormal
o
wear on the knives will result un-
less the lower knife ❻ is laterally
positioned and fixed at a posi-
tion where it has settled by itself
under the upper knife ❺ spring.
If the 15° angle of the lower knife
o
is exceeded, the durability of the
knife will be deteriorated, often
resulting in blade chipping.
If the angle is smaller than 15°,
o
the knife will be dull.
If the 62° angle is not observed,
o
the knife may catch materials.
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