Lewis 17 - Adjusting Thread Tensions

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12

ADJUSTING

THREAD

TENSIONS

34.

The

tension

on

the

needle

thread

is

adjusted

by

turning

thumb

nut

20-60,

Figure

C,

to

the

right

or

to

the

left.

This

tension

should

be

set

sufficiently

tight

to

make

a

firm

stitch.

Do

not,

however,

make

this

adjustment

too

tight,

because

by

so

doing

the

thread

will

draw

the

goods

and

leave

an

impres-

sion

or

dimple·

on

the

face

of

the

goods.

Also

thread

breakage

may

result

if

the

needle

thread

tension

is

set

either

too

loose

or

too

tight.

Figure

C

35.

The

tension

on

the

bobbin

thread

is

adjusted

by

means

of

screw

1046,

Figure

D.

By

turning

this

screw

to

the

right,

the

tension

is

set

tighter

as

it

presses

the

bobbin

case

spring

more

firmly

against

the

thread.

This

tension

should

be

set

rather

loose

so

as

to

permit

the

thread

to

draw

off

the

bobbin

freely

with

'very

little

resistance.

Experience

on

various

kinds

and

grades

of

work

will

show

]:>est

what

tension

produces

the

desired

results.

ADJUSTING

WIDTH

OF

BIGHT

FigureD

36.

The

width

of

bight

taken

by

the

needle

depends

on

severar

things,

the

"angle"

of

the

machine

being

the

most

important.

Thus

a

45°

machine

will

produce

a

wider

bight

than

a

15°machine,

other

conditions

being

equal.

The

width

of

the

bight

is

~lso

dependent

on

the

depth

to

which

the

needle

penetrates

the

'goods

as

well

as

the

shape

of

the

top

of

the

plunger.

For

any

'given

set

of

these

condi-

tiops,

the

width

of

bight

may

be

adjusted

by

moving

the

edge

guide,

Figure

E,

to

the

right

or

to

the

left

by

loosening

the

set

screw

which

holds

this

part

in

position~

By

moving

the

guide

to

the

left,

a

wider

bight

will

result,

to

the

right

will

produce

a

narrower

bight.

Figure

E

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