Singer 620 User manual

SINGER
CLASSES 620, 625, 626 AND 628

Supplement to
Form 20732 .
Machines 620, 625, 626 and 628
' (1066)
SINGER
SERVICE MANUAL
MACHINES OF CLASSES
620, 625, 626 AND 628
Instructions appearing in the Service Manual for Machines of Class 600 generally apply to
Machines of Classes 620, 625 and 626. Instructions for Class 603 Machines generally apply to
those of Class 628. This supplement provides instructions which apply only to Class 620 625
626 and 628 Machi nes.
THE SINCER COMPANY
* A Trademark of THE SINGER COMPANY
Insert in Form 20732, Swing Needle Service Manual
Printed in U. S. A,

INDEX
Bobbin Driver
Adjustment....
Removal and Replacement..—.
Bobbin Push-Button
Removal and Replacement__—.---
Chainstitch Adjustments.........
Hinge Assembly...-.
Hoolc, Rotating
Positioning...-.
Removal.
Replacing...-.
Timing...
Inspection and Lubrication...—.....
Needle-Threader Storage and Use...
Selector Systems
Release Mechanism.. . ....—-
The Cam Stack...-.-
Bight-Amplitude and Pattern Selector.
Needle-Bar Driving Arm.
Tension, Needle Thread
Adjustment.
Removal and Disassembly.
Reassembly and Reolacement.
Throat-Plate Position Bracket
Remove i ana R ss icc oment.
Winding Mechanism.
•Viring Dicgram.
9
9
9
20
5
8
6
6
7
3
22
12
14
17
19
10
10
10
PROPERTY OF
THE SINGER COMPANY
This is a private and confidential communication to and for the use only
of the employees of The Singer Company and its affiliated companies.
Reproduction, sale, distribution, or publication thereof to the public is
forbidden.
2

INSPECTION AND LUBRICATION
Before any extensive inspection is undertaken to
find causes of faulty operation, the machine should
be thoroughly cleaned and lubricated.
Remove lint, fluff, dust or other foreign particles
from the hook, feed dog, and bobbin case.
Remove bobbin case and clean in varsol. Open
face plate and clean out lint or waste collected
around needle bar, presser bar, and pressure regulator.
CLASS 620, 625 and 628 MACHINES
Remove arm too cover by opening stitch chart, re¬
moving screw, and sliding top cover toward left and
off the machine.
Remove arm top cover by removing the two screws
and lifting cover from machine.
Lay machine on back, loosen screws from the four
corners of the machine-bed cover, and remove cover
from underside of machine.
Wipe out any oil or grease accumulated inside
arm-toD and bed covers.
Oil machine as indicated below, and on pages
3, 4 and 5 for specific class of machine.
Apply one drop of oil between the casting and
the bobbin push-button release lever.

CLASS 626 MACHINES: This class of machine, supplied
only for use with the standard cam stack, does not require
the access means provided by the hinged top cover. Ac¬
cordingly, the following instructions do not apply to Class
626 Machines.
Removal
Remove top cover from machine as'described on
page 3.
Remove the two self-tapping screws on underside of
cover holding bracket to cover.
Remove holding ring from top lid.
Remove stitch indicator chart from lid.
Remove self-tapping screws in lid, disengaging
hinge.
Replacement
Fasten new hinge in lid with self-tapping screws.
Replace stitch indicator in top lid and secure it with
the holding ring-
Replace self-tapping screws through bracket. Do
NOT tighten securely.
Loosen adjustment screws in bracket.
Adjust lid so that it is flush with top cover. (This
is done by raising and lowering the lid on the slots
provided in the bracket while the adjustment screws
are loose, and by adjusting it to the left or right
while the self-tapping screws are loose in the over-
sized holes.)
When lid is correctly fitted, tighten the self-tapoing
screws and the adjustment screws in the bracket.
Replace cover and secure it with two cover screws.

THE ROTATING HOOK
VERTICAL GEAR
Removal
CAUTION: Hook-shaft gears and hand-wheel gea»
may be removed to facilitate adjustments. DO NOT
DISTURB THE MESH OF ANY OTHER GEAR IN
THIS MACHINE. All other gears are mated and cor¬
rectly timed. Replacements should be made only at
the factory.
Remove needle, presser foot, throat plate, bed
slide, bobbin case, feed dog, cushion-spring bracket,
and position finger.
Remove bed cover.
Remove feed-1 iftinq rock-shaft and feed rock-
shaft with pull-off finger as instructed on page 25,
Service Manual for Classes 600 and 603 Machines.
Remove actuating lever and bobbin driver as in¬
structed on page 9.
With chalk or crayon, mark the two bevel gears
as illustrated. (Mark one tooth of one gear, and the
corresponding space for that tooth in the other gear.)
This assures proper mesh when replacing.
Loosen set screw in vertical bevel gear, and re¬
move gear from hook shaft.
Lift rotating hook assembly from machine.
Replacement
InstalI rotating-hook assembly into machine. Using
the guide marks previous ly made, mesh vertical bevel
gear with horizontal bevel gear. Turn vertical hook-
shaft until flat side of shaft is under set screw in
bevel gear, and tighten set screw securelv.
Replace bobbin driver and actuating lever, as
instructed on page 9.
Insert pull-off finger into machine and reoiace
feed rock-shaft and feed-lifting rock-shatt as in¬
structed on page 25, Service Manual for v-lasses 600
and 603 Machines
Check and adjust hook as instructed on pages
7 and 3.
Replace all other parts previously instructed for
removal, except in reverse order.
6

To Time the Hook
Sot noodle bar at correct height, and time the
needle-bar vibrating mechanism as instructed on
pages 7 and 8, Service Manual for Classes 600 and
603 Machines.
Insert a Size 18 needle up into the needle clamp.
Remove throat plate, bed slide, bobbin case, and
bottom cover. It is not necessary to remove the feed
dog to time the hook.
Adjust machine for straight stitching in center
needle position.
Turn hand wheel over toward operator until lower
timing mark is aligned with lower edge of needle-
bar bushing on UPWARD STROKE of needle bar. At
this position, point of hook should be at center of
needle as illustrated.
To adjust, loosen the two set screws in horizontal
bevel gear. While maintaining position of needle bar,
turn vertical bevel gear at hook-end of shaft until
point of hook is in correct position. Then tighten
the two bevel-gear set screws securely, making cer¬
tain that gears are correctly meshed without binding.
CAUTION: Hub of horizontal bevel gear should
not contact face of bushing.
Replace throat plate, slide plate, bobbin case,
and bottom cover.
VERTICAL BEVEL SETSCREWS HCRIZONTAL 3 EV EL
\ SEAR
GEAR HUB SHOULD
HOT CONTACT FACE
OF BUSHING
7

To Position Hook to or from Needle
Set needle bar at correct height, and time the
hook as previously instructed.
Turn hand wheel until point of hook is directly
behind needle. When correctly set, the distance be¬
tween the needle and hook-point should be approx¬
imately 0.004 inch, as illustrated.
HOOK
POINT
SETTING: With bobbin push-button in winding
position, remove locator nut by turning in a CLOCK¬
WISE direction. Remove bobbin push-button assembly
(see instructions on poge 9), and remove locator.
Careful ly mark the two bevel gears, as illustrated,
to assure proper meshing of gears when replacing.
Then loosen set screw in vertical hook-shaft bevel-
gear and remove gear from shaft.
Loosen set screw holding the eccentric bushing.
Turn the eccentric bushing while maintaining posi¬
tion of hook, until correct distance between needle
and point of hook is attained.
Replace bevel-gear using the previously-made
guide marks to assure correct meshing of gears.
Replace all other parts in reverseorder instructed
for removal. Set winding mechanism as instructed
on page 9.
CAUTION: Check for binding or end play in hook
dri ving-s haft. F or adjustment and removal, see page
24 of Service Manual for 600 and 603 Machines, and
page 6 of this supplement for removal of hook.
s

WINDING MECHANISM
Bobbin Push-Button Assembly
Removal and Replacement
Open slide plate. Place push-button irr winding
position. Lay machine on back and remove bed cover
from machine. Remove locator nut from bobbin driver
by turning in a CLOCKWISE direction. Then remove
the two screws fastening the push-button assembly
to the underside of the bed. Slide assembly out as
a complete unit, being careful not to bend the push¬
button release lever.
To replace, follow the same directions as for
removal, except in reverse order.
Bobbin Driver
Removal and Replacement
Teen slide aiaTe. Remove ‘hroat plate, bobbin
cose, one ;ea cover. Per stitch enern seiecrcr ct p
•r.'cnes oer nen, one -pm non a -vneei jnri: eec
cog. is m its extreme 'ear oosinon. Remove iocaror
nut, pusn-button assembly, and locator. Then slide
bobbin driver up, rotate until apron is opposite feed
dog, and lift out of machine.
To replace, install bobbin driver in machine, ro¬
tating it until it seats firmly into place. Then replace
locator, push-button assembly, locator nut, throat
piate, and bobbin case.
Adjustment
To adjust the height of the bobbin driver, place
push-button in winding position and loosen adjustable
extension screw at end of lifting bracket. Press up¬
ward on bracket until bobbin rises slightly above top
of bobbin case. Then release upward pressure slight¬
ly, allowing bobbin to seat correctly into bobbin
case. Without disturbing this setting, tighten ex¬
tension screw securely
9