Flat Lock Sewing Machine: Parts, Specifications and Working Mechanism

Last Updated on 21/04/2021

Experiment name:
Study on flat lock sewing machine and production of sample.

There are many types of sewing machines. Some are used for special purposes such as bar tack machine, button hole machine etc. This type of machine works in a cycle and so they are called simple automatic machine. Here we study on such a type of machine that is flat lock sewing machine. It is also called flat bed sewing machine. Flatlock machine has a vast working space permits a wide range of sewing applications and is utilized for all types of flat sewing work. The flatlock stitch is sewn by flat lock sewing machine. It is used in swimwear, sportswear, on baby’s clothes.

Flat Lock Sewing Machine
Fig: Flat Lock Sewing Machine


  1. To know about the machine parts of flatlock sewing machine.
  2. To know specification and working mechanism of flat lock sewing machine.


  • Brand                     : JUKI
  • Model                    : MFD 47605U
  • Type                       : Flat or Cylinder bed
  • Group                     : Chain stitch
  • Needle no              : 3
  • Needle name: UY-128
  • Needle size: 9, 11, 14, 16, 18, 20 & 21
  • SPM                       : 2500-6000
  • TPI                         : 25-35

Thread, tension, needle, pressure feed, stitch density, looper etc.

Sewing all types of knitted cloth.

Different parts of flatlock sewing machine:
The majority of the flatlock machine parts remain common as discussed in overlock sewing machine.

  1. Thread stand
  2. Thread guides
  3. Disc type tensioner
  4. Pressure feed lever
  5. Thread take-up lever
  6. Needle
  7. Looper

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. For example for sewing 1 inch cloth up to 32 inches 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.

Working mechanism of flatlock machine
The flatlock sewing machine gets drive from the electric motor which is mounted in sewing table. The main parts of the sewing machine are flywheel, main shaft, needle bar, loopers, feed dog and presser foot.

Flat lock sewing machine – Top and bottom main shaft
Fig: Flat lock sewing machine – Top and bottom main shaft

The motion from the main shaft is directly connected with the needle bar mechanism. A link from the main shaft is taken to spreader mechanism with a cam. The cam rotation is fixed as half revolution per every full rotation of the main shaft. So that, the spreader movement is controlled.

The knee presser foot lifter mechanism is also connected to presser foot bar in the top side. By a ‘V’ belt, the drive is transferred to the bottom of the machine and the bottom shaft is directly connected to the feeding mechanism. The bottom shaft also controls the movement of the bottom looper. A cam attached with the bottom acts as a tensioner device which controls the sewing thread supply to the bottom looper.

Flatlock sewing machine cannot be used for normal purpose. But for making a complete garment their importance can not be denied. Special care and sufficient knowledge is necessary for proper working. Otherwise faulty sewing may be done. I would like to give special thanks to our teacher. I am also grateful to our instructors. I think this will be very helpful in my future life.


  1. Apparel Machinery and Equipments By R. Rathinamoorthy and R. Surjit
  2. Apparel Manufacturing Technology By T. Karthik, P. Ganesan and D. Gopalakrishnan

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