Singer QuantumLock User manual

Three-Thread Overlock
(Narrow, Wide, and Wide
with Decorative Threads)

Three-Thread Overlock (Narrow)
The Three-Thread Overlock Stitch is the most commonly used stitch because of
its versatility. It provides a wonderful professional seam finish to woven fabrics. It is
beneficial in preventing loosely woven fabrics from unraveling. In addition, the
Three-Thread Overlock Stitch offers unlimited decorative capabilities. It is
recommended for finishing seams but not reinforcing the seam. Use the conventional
sewing machine’s straight stitch to reinforce the seam. The stitch uses one overedge
needles and both the upper looper and lower looper. There are 2 different ways to set
up for a Three-Thread Overlock stitch. For a more narrow stitch (4.0) select the Right
Overedge needle; for a wider stitch (6.0) the Left Overedge needle is used.
Upper Looper Thread
Lower Looper Thread
Right Overedge Needle Thread
Three-Thread Overlock (narrow) page 1

ATD:
Auto Tension Dial
“A”
Left Cover Stitch
Needle “C”
Unthreaded and
Remove Needle
Middle Cover Stitch
Needle “D”
Unthreaded and
Remove Needle
Right Cover Stitch
Needle “E”
Unthreaded and
Remove Needle
Overedge Left
Needle “A”
Unthreaded and
Remove Needle
Overedge Right
Needle “B” (Blue)
Threaded
Upper Looper
(Green)
Looper Engaged
and Threaded
Lower Looper
(Red)
Threaded
Chain Stitch Looper
(Brown)
Unthreaded
Upper Knife Engaged
Seam Guide Plate Not Installed, use
Knife Cover Plate
Seam Width Dial “N”
Stitch Length Dial “2”
Presser Foot
Pressure
“N”
Differential Feed Dial “N”
Stitch Finger “N”
Spreader Not Used
Set-up:
Needle:
Three-Thread Overlock (narrow) page 2

The Three-Thread Overlock
makes a great edge finish to a
garment’s facing.
Three-Thread Overlock (narrow) page 3

Three-Thread Overlock (narrow) page 4
Turn Auto Tension Dial to “A”.
Turn Stitch Length Dial to “2”.
Engage Upper Knife. The knife will not trim the fabric when it is disengaged.
1. Open Looper Cover.
2. Pull the movable knife holder (silver screw) to the right as far as it will go.
3. Turn the holder clockwise until the knife clicks into a lock position.
Upper Knife EngagedUpper Knife Disengaged

Turn Presser Foot
Pressure Dial to “N”.
Turn Differential Feed
Dial to “N”.
Turn Seam Width Dial
to “N”.
 Set Stitch Finger to “N”.
Three-Thread Overlock (narrow) page 5

Install the Knife Cover.
Engage Upper Looper. Engaging the Upper Looper causes the looper move when
sewing. Even though the Upper Looper is not threaded it needs to be engaged.
1. Push the clutch button to the left and down to engage.
2. Turn handwheel.
Upper Looper Disengaged
Upper Looper Engaged
Three-Thread Overlock (narrow) page 6

Two-Thread Overedge (narrow) page 7
Disengage Spreader. The Upper Looper has a hole for the thread on the top of the
looper. If the stitch requires that the looper be engaged but not threaded, then the
Spreader is used. The Spreader simply plugs-in (or closes) the looper’s hole. The
Spreader is disengaged when the Upper Looper is engaged/operative and threaded.
The Spreader is used with a stitch that requires only one looper thread. With
the help of the Spreader, the single looper thread wraps around the fabric’s
edge.
1. Lower the white handle on the Spreader to open the eye of the Upper
Looper.
Thread Upper Looper with regular overlock thread.
1. Raise the Presser Foot to release the
tension disks. Thread the Lower
Looper as illustrated 1-9.
2. Pass thread from back to the
front through the thread
guide.
Spreader Engaged Spreader Disengaged
Eye of Looper

3. Thread the top cover thread guide by pulling the thread towards the left until
it slips under the guide. Then pull the thread along the right side of the
button as illustrated.
4. While holding the thread, firmly pull the thread between the tension disks.
5. Turn the handwheel toward you until the lower looper extends 5-10mm
(approximately ½”) from the needle plate edge.
6. Thread the looper area of the machine following the green color coded
thread guides 4-9.
Three-Thread Overlock (narrow) page 8

7. Thread the hole in the Upper Looper from front to back . Pull about 4
inches of thread through the looper and place to the back of the
throat plate.
Thread Lower Looper with regular overlock thread.
1. Raise the Presser Foot to release the tension disks. Thread the Lower
Looper as indicated 1-10.
2. Pass thread from back to the front
through the thread guide .
3. Thread the top cover thread guide by pulling the thread towards the left until
it slips under the guide. Then pull the thread along the right side of the
button as illustrated.
Three-Thread Overlock (narrow) page 9

4. While holding the thread, firmly pull the thread between the tension disks.
5. Turn the handwheel toward you until the lower looper extends 5-10mm
(approximately ½”) from the needle plate edge.
6. Thread the looper area of the machine following the red color coded
thread guides 4-10.
7. Place the thread slighty from left and
to the right of threading guide .
8. Place the thread slightly from the
front and to the back of threading
guide .
9. Place the thread through , and .
Three-Thread Overlock (narrow) page 10

Three-Thread Overlock (narrow) page 11
10. Thread the looper eye (A) from front to back. Pull about 4 inches of thread.
Position thread into V cutout (B) on threader. Firmly hold thread tail with left
hand and pull Threader Lever (C) up into place (D).
NOTE: Make sure the Upper Looper thread is
behind the Lower Looper thread.
Threader Lever
“V” cutout

Thread Right Overedge needle with regular thread.
1. Raise the Presser Foot to release the tension disks. Thread the right
needle as indicated 1-9.
2. Pass thread from back to the front
through the thread guide .
3. Thread the top cover thread guide by pulling the thread towards the left until
it slips under the guide. Then pull the thread along the right side of the
button as illustrated.
4. While holding the thread firmly, pull the thread between the tension disks.
Three-Thread Overlock (narrow) page 12

5. Continue to thread points 4-8. Slip the thread into the rear slot of the
thread guide . Go over the take up lever . Continue by slipping the
thread into the right slot of the thread guides and .
8. Before threading the eye of the needle, make sure the thread is
behind the thread guide located on the bottom of the needle clamp.
9. Draw about 4 inches of the thread through the needle eye towards the back
of the machine.
10. Place the thread to the back, under the Presser Foot.
Three-Thread Overlock (narrow) page 13

Align one piece of medium weight fabric so
that the knife just slightly trims the fabric edge.
Sew.
Align a second piece of medium weight fabric
so that the knife just slightly trims the fabric
edge.
Place the two fabrics, right sides together.
Using a conventional sewing machine, sew a
straight stitch with a ⅝inch seam.
Press the seam open.
Three-Thread Overlock (narrow) page 14

Three-Thread Overlock (Wide)
The Three-Thread Overedge (wide) has the same set up as the Three-Thread Over-
edge (narrow) Stitch. The only exceptions are the Right Overedge Needle is now
unthreaded and removed and the Left Overedge Needle is threaded. By using the
left needle the stitch becomes wider. The other exception is the Auto Tension Dial
is turned to “B”.
Three-Thread Overlock (wide) page 1
Right Overedge Needle Thread
Left Overedge Needle Thread

ATD:
Auto Tension Dial
“B”
Left Cover Stitch
Needle “C”
Unthreaded and
Remove Needle
Middle Cover Stitch
Needle “D”
Unthreaded and
Remove Needle
Right Cover Stitch
Needle “E”
Unthreaded and
Remove Needle
Overedge Left
Needle “A” (Orange)
Threaded
Overedge Right
Needle “B”
Unthreaded and
Remove Needle
Upper Looper
(Green)
Looper Engaged
and Threaded
Lower Looper
(Red)
Threaded
Chain Stitch Looper
(Brown)
Unthreaded
Upper Knife Engaged
Seam Guide Plate Not Installed, use
Knife Plate Cover
Seam Width Dial “N”
Stitch Length Dial “2”
Presser Foot
Pressure
“N”
Differential Feed Dial “N”
Stitch Finger “N”
Spreader Disengaged
Set-up:
Needle:
Three-Thread Overlock (wide) page 2

Thread Left Overedge needle with regular thread.
1. Raise the Presser Foot to release the tension disks. Thread the
left needle as illustrated 1-9.
2. Pass thread from back to the front
through the thread guide.
3. Thread the top cover thread guide by pulling the thread towards the left until
it slips under the guide. Then pull the thread along the right side of the
button as illustrated.
4. While holding the thread firmly, pull the thread between the tension disks.
Three-Thread Overlock (wide) page 3

5. Continue to thread points 4-8. Slip the thread into the middle slot of the
thread guide . Go over the take up lever . Continue by slipping the
thread into the middle slot of the thread guides and .
6. Before threading the eye of the needle, make sure the thread is behind
the thread guide located on the bottom of the needle clamp.
7. Thread the eye of the left needle .
8. Draw about 4 inches of the thread through the needle eye towards the back
of the machine.
9. Place the thread to the back, under the Presser Foot.
Three-Thread Overlock (wide) page 4

Turn Auto Tension Dial to “B”.
Turn Stitch Length Dial to “2”.
Align one piece of medium weight fabric so
that the knife just slightly trims the fabric edge.
Sew.
Three-Thread Overlock (wide) page 5