Flat lock machines are specialized, high-speed machines that use two or more needle threads to form stitches by passing through fabric and interlocking on the top and bottom sides. They have multiple needles, loopers, and spreaders and can sew at speeds up to 6000 SPM. Flat lock machines are mainly used for sewing knitted garments but can also be used for woven fabrics. They require numerous thread types and adjustments to operate properly.

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3. Flat Lock Machine
Flat lock machines are specialized, high-speed machines.
These machines are extremely fast and efficient. In this
machine the stitch is formed by two or more needle threads
passing through the material, inter looping on the
underside and interlocking on the upper side. These
machines are mainly used for knits.
Elements in Stitching
1. Needle
2. Looper
3. Spreader
 Multi Needle machine have more than three needles.

4. Loopers:
Loopers are available in different shapes respective of
their machines. Looper may or may not carry the lower
thread in the formation of stitch. As in case of flat lock
looper holds the lower thread but in case of single needle
chain stitch it holds the needle thread.
Spreader:
Spreader work in conjunction with a looper to assist
in the loop formation. They in fact move the thread but did
not carry the thread

5. Specifications
 Function : Sewing all type of knitted cloth
 No. of needle : up to 4
 Needle Size : 9, 11, 14, 16, 18, 20 & 21
 No. of threads : 4 to 9
 SPM : 6000
 Type : Flat or cylinder bed
 Stitch Density : 8 to 16 per inch
 Thread consumption of this machine is very high. So very
expensive machine.
 Used for knitted garments. But it can be used for Woven
garments.

6.  Adjustment : Thread, Tension, Needle, Pressure,
Feed, Stitch density, Looper etc…….
 Different parts : Thread stand, Thread guides, Disc
type tensioner, Pressure feed lever, Thread take-up
lever, Needle, Looper…..

7. Description
 This machine may be of flat bed or cylinder bed type.
 In our lab 21, 22 nos. machines are flat bed and 32 no.
machine is cylinder bed type.
 Flat bed is used for sewing body cloth and cylinder bed is
used for sleeve cloth.
 In this machine 4 needles may also be used and sewing may
be done using from 4 to 9 threads.
 Sewing with flat lock machine the most quantity thread is
needed.
 The SPM of this type of machine is usually 6000 and 8-16
stitches may be done per inch.
 It is a very expensive machine and is used for mainly sewing
knitted goods but also used for making woven cloth.

8. SPREADER

9. LOOPER

10. TAKE UP MOTION

11. 4-Feeding Systems
Feeding mechanisms are of 8 types
1. Drop feed
2. Differential feed
3. Needle feed
4. Adjustable Top feed
5. Compound feed
6. Puller feed
7. Walking foot feed
8. Manual feed

12. Needle Feed Adjustable Top Feed
Unison Feed

13. Puller Feed Walking Foot

14. Differential-feed micro-adjustment
mechanism
 It is possible to finely adjust the differential feed
amount to a best-suited value for the material to be
used. In addition, the differential feed ratio remains
the same even when the stitch length is changed.

15. Micro-lifter mechanism
 Elastic material or delicate material can be sewn with the
presser foot kept slightly raised. This effectively helps
reduce the degree of slippage, warpage and damage of the
material.

16. Stitch length adjusting mechanism
 Stitch pitch (stitch length) can be adjusted with ease
simply by turning the stitch dial.

17.  Chain stitch machine : Stitch class 401
USES: Waist band & Inseam of jeans.
 Flat lock/ Inner lock M/C : Stitch class: 406
(3thread), 407 (4 thread), 602 (4 thread), 605
(5thread).
USES: Bottom & sleeve hem of T-shirt & Polo shirt.

18. Technical adjustments of Flat lock machine
 1. Basic Machine Practice
 2. Technical Specification
 3. Installation of needle
 4. Needle bar Height adjustment
 5. Main looper timing
 6. Spreader Looper Adjustment
 7. Stitch Length Adjustment
 8. Feed Dog Height adjustment
 9. Cam Timing (Thread)
 10. Needle and looper guard adjustment

19. Flat locking Facts:
 Flat locking is a decorative stitch.
 Use the standard presser foot.
 Disengage the upper blade so the folded fabric will not be cut.
 Use the left needle for the widest flat lock stitch.
 Decorative thread usually goes in the upper looper.
 Stitching is done on the fold of the fabric.
 Wrong sides of the fabric are folded together in order for the loops to
show on the right side.
 Right sides of the fabric are folded together in order for ladder stitches
to show on the right
 side.
 Flat locking on a folded edge creates a decorative stitch through the
middle of the fabric piece.

20. THREADING PROCEDURE FOR
F/L

32.  Stitches are formed by two or more groups of threads.
 One group is called needle thread and another is
called looper thread
 Threads are bound together by interlacing and
interlooping.
 Multi thread chain stitch is also called double locked
stitch.
 Possibility of seam pucker formation is less.
 Extensibility is same as lock stitch.
 Used for long length sewing, heavy fabric sewing
attaching lace, braid, elastic etc...

33. Stitch class – 600 ( Multi – thread
chain stitch )
 Stitches under 600 class are formed by three groups
of threads.
 One group is called needle and other is called top
cover thread and the other group is called bottom
cover thread.
 Stitches under this group are very complex and may
need up 9 threads.
 Used for making knitted undergarments to attach
tape, lace, elastic.
 Also used for decorative purposes

34. 406
401
-Chain stitch
Stitch formed by 1
needle thread and
being
Inter looped with 1
looper thread that is set
on the
underside of the seam.
Bottom Coverstitch
Stitch formed by 2 needle
threads passing
through the material and
interlooping with 1 looper
thread with the stitch set
on the underside of the
seam. Looper thread
interlooped between
needle
threads, providing seam
coverage on the bottom
side.

35. 605
Coverstitch
Formed with 3-
needle threads, a top
cover
thread and a bottom
looper thread.
607
Coverstitch
Formed with 4-needle
threads, a top cover
thread and a bottom
looper thread.