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" l{anrow
Roll
0veredging by
8[5-407"
Change
of
the
'standard
throat
plate'
with
the
'extra
throat
plate' turns
Model BL3-407
ready
for
3-thread narrow
roll
overedging.
How
to
change
the
throat
plate
1.
Bring
the
needle
to
the
uppermost.
Remove
the
presser
foot.
Open
both knife
cover
and
side cover.
5.
6.
7.
Loosen
both
of
the
lower
knife
holder fixing
screws
and
move
the
lbwer
knife
holder slight-
ly
righturard together
with
the
lower
knife.
(See Figure
44,
Page
18,
lnstruction
Booklet)
Remove
the
'standard
throat
plate' and
set
the'extra
throat
plate'in
place.
Move back
the
lower
knife
holder
to
place and
tighten both
of
the
lower
knife
holder fixing
screws.
Make sure
to
level
the
tip
of the
lower
knife
blade
exactly
flat
with the
surface
of
the
new
throat
plate.
Set
back the
presser
foot.
Set
the
stitch
length
about
1
-
'l
.5 mm.
(See Page
17,
lnstruction
Booklet)
Close
both knife
cover
and side cover.
Thread tension
adj
ustment
Narrow
roll
overedging
is
available
in two
vari-
eties
depending
on the
balance
of
the
thread
tension
levels.
Standard:
This
has
the
same seam
structure
as
the
ordi-
nary
overedgings
except
for
the
extraordinary
narrowness
of
the bight
(overedge)
width
and
the
rolled-in
edge
of
the
sewn
material.
Make
adjustment
with
reference
to
Figures
30
-
33
in
Instruction Booklet
(Page
13
-
14).
Variation:
This
is
obtained
when the tension
balance
of
'standard'
narrow
roll
overedging
is
deliberate-
ly
imbalanced
by
tightening
up the
lower
looper thread while
loosening
down
the
upper
looper thread,
each
to
an
enough
extent to
render
a
typical outlook of
the stitches
sketch-
ed
as
below:
standard
Tighten upper looper thread tension.
When needle
thread
laps
round
over
the
face
Tighten
needle
thread
tension
or
loosen
both
upper and lower
looper
thread
tensions.
2.
3.
4.
When
lower
looper thread
laps
round
ov6r
the
back
Face
Tighten lower looper thread
tension
or
loosen needle
thread
tension.
ffi
variation
Make
'variation' narrow
roll
overedging with
reference
to
the
seam
diagrams
right:
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