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Helpful hints about sewing
Basic knowledge about the overlock machine
Throat plate for the overlock machine

The overlock machine is a basic type of sewing machine that is a lockstitch machine.
The lockstitch machine can be used for sewing any part of a sewing product. The overlock machine, however, has a specific feature of sewing in the edge of one or two pieces of material fabric while cutting and hemming the edge.
With this feature, the overlock machine is usually used for preventing the fabric edge from raveling and for sewing heavy-weight products such as car mats and highly elastic knits.
Typical stitch systems of the overlock machine are 1-needle overlock, 2-needle overlock and 2-needle safety stitch (Fig. 1).

Fig. 1 Kinds of overlock machines
1-needle overlock
1-needle, 3-thread
Stitch style: 504
Application: Runstitches for general fabric and knits
MO-6x04 Series
2-needle overlock
2-needle, 4-thread
Stitch style: 514
Application: Overedging for knit fabric with a wider overedging width
MO-6x14 Series
2-needle safety stitch
2-needle, 5-thread
Stitch style: 515
Application: Safety stitch for men's shirts, fabric and knits
MO-6x16 Series
1-needle overlock 2-needle overlock 2-needle safety stitch


1. Kinds of throat plates for the overlock machine

In this issue, components of the throat plate for the overlock machines are described (Fig. 2).
The throat plate differs with the aforementioned three kinds of stitch systems.

Fig. 2 Throat plate for the overlock machine
1-needle overlock
MO-6x04 Series
2-needle overlock
MO-6x14 Series
2-needle safety stitch
MO-6x16 Series
1-needle overlock 2-needle overlock 2-needle safety stitch


2. Configuration and function of throat plates for the overlock machine

(1) Configuration and function of the throat plate for the 1-needle overlock machine
The throat plate for the overlock machine is as illustrated in Fig. 3.

1) Location of the auxiliary feed dog teeth
•The auxiliary feed dog teeth helps produce chain-off thread with consistency.

2) Overedging width
•The overedging width (Fig. 4) differs with the width of the overedging claw.
A - The claw width determines the overedging width.
B - Thread tension varies according to the entire length.
C - Needle entry

3) Location of a cloth cutting knife
•The fabric is cut here. The cutting width is determined by the location of the knife.

4) Feed dog groove
•The feed dog for the 1-needle overlock machine comes in three different types, i.e., feed dog with 1 row of teeth, feed dog with 2 rows of teeth and feed dog with 3 rows of teeth.
•Efficiency of feed and straight feeding capability of the feed dog increases with the number of teeth.
•The feed dog with 1-row teeth is characterized by its ability to support sharp-curve sewing.

5) Throat plate slot
•The slot prevents the feed mechanism from returning (in prevention of an uneven pitch).
The slot also works to improve the differential effect.

Fig. 3 Throat plate for the overlock machine Fig. 4 Overedging width
Fig. 3 Throat plate for the overlock machine Fig. 4 Overedging width


(2) Configuration and function of the throat plates for the 2-needle overlock machine
The throat plate for the overlock machine is as illustrated in Fig.5.

1) Needle entry section
The structure of the needle entry section is as illustrated in Fig. 6.

2) Feed dog groove
•The feed dog for the 2-needle overlock machine comes in three different types, i.e., feed dog with 2 rows of teeth, feed dog with 3 rows of teeth and feed dog with 4 rows of teeth.

Fig. 5 Throat plate for the 2-needle overlock machine Fig. 6 Structure of the needle entry section
Fig. 5 Throat plate for the 2-needle overlock machine Fig. 6 Structure of the needle entry section
D - Overedging width, E - Needle width,
F - Right needle, G - Left needle

(3) Configuration and function of the throat plates for the 2-needle safety-stitch machine
The throat plate for the safety stitch machine is as illustrated in Fig.7.

1) The right side of the main feed dog teeth feeds thread to form double chain stitches
(This part is important for producing chain-off thread stitches.)

2) Needle entry of double chain stitches
The slot in the rear side of the throat plate has two roles. The first role is to tense the needle thread with a lower thread tension application. The second one is to prevent stitch skipping when producing chain-off thread.

Fig. 7 Configuration of the throat plate for the safety stitch machine
Fig. 7 Configuration of the throat plate for the safety stitch machine


3.Other stitches produced by the overlock machine


1) Overlock machine

1-needle, 2-thread Stitch style: 503
Application: Decorative stitch for handkerchiefs, serging, etc.
1-needle, 3-thread Stitch style: 505
Application: Bottom hemming
2-needle, 4-thread Stitch style: 512
Application: Imitated safety stitch for general fabric
1-needle, 2-thread Stitch style: 503 1-needle, 3-thread Stitch style: 505 2-needle, 4-thread Stitch style: 512

2) Safety stitch

2-needle, 4-thread Stitch style: 515
Application: Safety stitch for fabric including men's shirts and knit fabric
3-needle, 6-thread
Application: A 3-needle, 6-thread machine is able to sew two different stitches, i.e., an overlock stitch and a double chain stitch. It is characterized by its wide overedging width and durable seams.
When the needle for the double chain stitch is removed, leaving two needles, the machine can be used as a 2-needle overlock machine. When one of the two needles for the 2-needle overlock stitch is removed, the machine can be used as a safety stitch machine with a wide overedging width.
2-needle, 4-thread Stitch style: 515 3-needle, 6-thread

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