Singer CLASS 20 User manual

20533
ADJUSTERS
MANUAL
SINGER
SEWING MACHINES
CLASS 20
SINGLE THREAD CHAIN STITCH
THE SINGER MANUFACTURING COMPANY
Copyright, U. S. A., 1936, 1952 and 1954, by The Singer Manufacturing Company
All Rights Reserved for all Countries
*A Trade Mark of THE SINGER MANUFACTURING COMPANY

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£22788
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Fig. 2. Principal Parts of Machine 20-10
Thread Hole in Tension J. Clamp Screw
Bracket K. Stitch Regulator
Tension Discs L. Looper
Tension Regulating M. Cloth Plate
Thumb Nut N. Presser Foot
Thread Nipper ©. Cloth Guide Thumb Screw
Spool Pin 45P. Cloth Guide
Thread Pull Off Q. Needle Set Screw
Hand Wheel R. Presser Bar Lifter
Driving Handle S. Presser Bar
T. Needle Bar
Clamp

3
DESCRIPTION
Machines of Class 20 are practical, convenient, single thread
chain stitch sewing machines made especially for children. They may
also be used by adults for repairing clothes and light household
articles.
Machines 20-1 and 20-10 are operated manually. Machine 20-2
is operated by motor, although it too can be operated manually by
removing motor and attaching a handle to hand wheel.
All Machines of Class 20 have a cloth guide for use when sewing
close to edge of material.
The rotary looper makes one revolution per stitch.
The needle is threaded from left to right.
.. An arm side cover encloses movable parts of arm of Machine
20-10. ^ o4 i
A clamp, for fastening machine to a table or desk, is furnished
_ with all Machines of Class 20.
All electrical parts of motor of Machine 20-2 are enclosed in a
bakelite shell, eliminating the danger of electrical shock.
The motor requires no attention except occasional oiling. It must
be used only on 110 volt, 60 cycle, alternating current (A. C.).
TO PREPARE MACHINE FOR SEWING
1. Inspect for possible damage incurred during transit. Bent shaft,
broken wheel, etc.
Check machine for free turning qualities.
Rinse with Varsol, then wipe off all traces of tacky, anti-rust oil
used to protect polished and plated surfaces.
Oil machine completely. See page 14. Wipe away any surplus cil.
5. Check condition of needle before making sewing tests. See item
` 4, top of page 15.
6. Check timing of feed and position of looper in relation to needle.
See page 9.
7. Check looper shaft for correct amount of end play. See page 9.
Check hand wheel for correct amount of end play. See page 13.
Glazed cotton thread is recommended for improved sewing results.
10. Sew-in machine and check stitching. See page 8.

DESCRIPTION OF 24X 1 NEEDLES
Needles for Machines of Class 20 are of Class and Variety 24 x 1
in Sizes 9, 11, 14 and 16.
The size of needle to be used depends upon the size of the thread
which must pass freely through eye of needle.
— iae
Do not use rough or uneven thread or thread which passes with
difficulty through needle eye, as such thread will interfere with the
successful use of the machine.
Although needles are made with different diameter of blades,
certain dimensions remain constant for all needles of the same Class
and Variety.
FLAT
SIDE
BLADE
. LL
OF
SHANK
i
-L——
j
|
£20961
E
E
NEEI
Fig.
3.
Needle
Distances
For example, the distance X between the short-grooved side of
needle blade and the position of the flat-side of the needle shank,
seated in needle bar, is constant, maintaining an identical relation-
ship between short-groove side of all 24 x 1 needles and looper point.
Therefore, any increase in diameter of blade results in a shifting of
only the centerline of needle blade away from looper point.
Another constant is distance Y from end of shank to top of eye,
maintaining an identical relationship between needle eye and looper
point, during formation of thread loop.
However, the size of needle eye increases with the size of needle
to accommodate heavier thread. Therefore, any increase in the length
of a 24 x 1 needle is made from the top of the needle eye toward the
point of the needle.

HOW TO CHECK A
= NEEDLE FOR STRAIGHTNESS
Plaċe flat side of needle on cloth
plate or any other flat solid surface
PER and hold up to light, as shown in
Fig. 3A. A straight needle will show
an even amount of light under it
and point will be in line with shank.
Fig. 3A. Checking Needle
TO SET NEEDLE IN NEEDLE BAR
Turn hand wheel over MOVE TO
away from operator until ONT
needle bar reaches its high-
est point. Loosen needle set
screw A, Fig. 4. With flat
side of needle to the right, INSERT
Baza ; NEEDLE UP
as shown in Fig. 4, insert AS FAR AS
needle up into needle bar POSSIBLE
as far as it will go and
tighten set screw A,
pe
Fig. 4. Setting the Needle

FORMATION OF SINGLE THREAD CHAIN STITCH
NEEDLE
OF
LOOPER LOOPER LOOPER LOOPER
Fig. 5. Looper Entering Fig. 6. Loop Being Carried
Loop of Needle Thread Through Previous Loop
Fig. 5 shows the first stage in stitch formation. The needle, after
descending to its lowest point, has been slightly raised and a loop
of thread is thus formed which is immediately entered by point of
looper and carried by it into the preceding loop.
Fig. 6 shows the second stage. The loop of thread is being car-
ried by point of looper down through preceding loop. The heel of
looper is about to release preceding loop.

FORMATION OF SINGLE THREAD CHAIN STITCH (Continued)
s LEED
ESE ea
LOOPER
Fig. 7. Loop Enlarged and Fig. 8. Loop Further Enlarged
Previous Loop Drawn Up and Previous Loop Completed
Fig. 7 shows the third stage. The loop is further enlarged by the
downward movement of point of looper. The preceding loop has been
released and is being drawn closer to fabric by movement of looper,
assisted by the raising of needle bar.
Fig. 8 shows the completed stitch. The loop of the stitch in process
is drawn down to its fullest extent by looper. The preceding stitch
has been drawn closely againstthe underside of fabric and is com-
pleted, the needle bar having reached its highest point.

TO REGULATE TENSION ON THREAD l d
Tension on thread, =
once regulated, seldom re-
quires changing.
The thread nipper
spring B, Fig. 9 is automat-
. Jcally controlled by needle
- bar lever at C, Fig. 9. The
nipper is opened just be-
fore needle bar reaches its
highest point and remains
open until needle bar has
drawn off sufficient thread
for next stitch.
The thread nipper
should open to approxi-
mately 1/32" when needle
bar is at its highest point. Fig. 9. To Regulate Tension
If puckering or thread breakage occurs at light tension settings,
raise needle bar to highest point and check nipper opening. If neces-
sary, reshape contact finger of nipper so that correct opening is
obtained.
If stitches are so tight that they pucker material, decrease tension
by turning thumb nut E, Fig. 9 over to the left (counter-clockwise). If
stitches are too loose, increase tension by turning thumb nut E over to
the right (clockwise).
Note:—lf thread bearing surfaces are rusted, they should be
replaced.
TO REGULATE LENGTH OF STITCH
The length of stitch is
regulated by lever F, Fig. 10.
For a longer stitch, move lever
F down away from operator.
For a shorter stitch, move lever
F up toward operator.
Fig. 10. To Regulate Length of Stitch

TO TIME FEED AND LOCATE FEED
ECCENTRIC AND LOOPER
NOTE: If screw L is loosened, all adjustments (timing feed and
locating feed eccentric and looper) must be made as instructed below.
Fig. 11. Timing the Feed
To time feed, turn hand wheel over away from operator until
looper point is centered with needle, as shown at M, Fig. 11. Loosen
set screw L, Fig. 11 and turn feed eccentric K so that screw L is in
position shown in Fig. 11.
To locate feed eccentric K, hold pinion gear Q, Fig. 17 against
machine and adjust feed eccentric K for a slight amount of clearance
(not to exceed .003 inch,) as shown in Fig. 11A. Do not tighten screw L
at this time.
To locate looper R, move looper as
close to needle as possible as shown at
D, Fig. 11A, and then, after all adjust-
ments have been made as instructed
above, tighten set screw L, Fig. 11. Re-
check adjustments.
Fig. 11A. Locating Feed
Eccentric and Looper
TUse .003 Feeler Gauge Serial 187928 Complete.

>
TO REMOVE AND REPLACE CLOTH PLATE
To remove cloth plate U, Fig. 12, first remove thumb screw T
and cloth guide Y. Raise presser bar and needle bar to highest points.
Remove screws Z. Lift cloth
plate slightly at U (to clear
feed dog) and slide it out
between presser foot and
feed dog.
mar
To replace, raise presser
bar and needle bar to high-
est points. Pass cloth plate
between presser foot and
feed dog, fit cloth plate
slots over feed dog teeth
and replace cloth plate
screws Z. Replace cloth
guide Y and thumb screw
T.
Fig. 12. Removing and
Replacing Cloth Plate
TO REMOVE AND REPLACE LOOPER
CAUTION: When removing looper, needle must be high enough
for looper to pass without striking needle.
To remove looper R, turn hand wheel over away from operator
until set screw L is in approximate position shown in Fig. 13. Loosen
screw L and remove looper R from end of looper shaft S.
Fig. 13. Removing Looper
To replace looper, turn hand wheel until needle bar is at its
highest point. Fit looper R (point down) into slot in looper shaft S.
Time feed and locate feed eccentric K and looper R, as instructed on
page 9.