Thread Path, Parts & Main Adjustment Points of Overlock Machine

Last Updated on 17/04/2021

Experiment name:
Study of thread path, main adjustment points of different industrial overlock machine and production of sample.

There are many types of sewing machine. Some are used for special purposes such as overlock machine, bar tack machine, button hole making machine etc. Overlock machine is also called serger. A serger is an overlocker. An overlocker is a serger. This type of machines works in a cycle and so these are called simple automatic machine. Here we study on such a type of machine that is overlock machine. Overlock machines are specialized machines that make the overlock stitch. The overlock stitch is used for edge finishing and seaming. Overlock machines come in both home and industrial versions.

overlock stitch
Fig: Overlock stitch


  1. To know about the machine parts of overlock machine.
  2. To know about the thread path of overlock machines.


  • Name                     : Industrial overlock machine.
  • Types                     : 3, 4 & 5 threads
  • Brand                     : JUKI
  • Model                    : MO-3614 (4 thread)
  • SPM                       : 6500-8500
  • TPI                         : 15-16 (3), 17-18 (4) & 21-22 (5)
  • Needle no              : 1 needle, 2 loopers (3); 2 needles, 2 loopers (4) & 2 needles, 3 loopers (5)
  • Needle name        : DCX1
  • Needle size            : 9, 11, 14, 16, 18, 20 & 21

Main parts of overlock machine:

parts of overlock machine
Fig: Parts of overlock machines
  1. Thread stand
  2. Thread package
  3. Thread guide
  4. Disc type tensioner
  5. Thread guides
  6. Needles
  7. Loopers
  8. Thread cutter

Mainly over edge machines are overlock machines. In this type of sewing machines there are one or two needles and edge-trimming knife is at the front of needle. To make over lock stitch 2-5 threads are used. Usually SPM of over lock machine is 6500. But SPM of 8500 machines are also found. In this machine there also stretching (stretching max 1: 0.6) and gathering (gathering max 1: 4) systems during feeding cloth. Stitch is done up to maximum 4 mm length and stitch length may also be changed by push button. This type of machines can be used for sewing for both woven and knitted cloths.

thread path of overlock machine
Fig: Thread path of overlock machine

Adjustments Points of Overlock Machine

  1. Basic Machine Practice
  2. Technical Specification
  3. Installation of needle
  4. Needle bar height adjustment
  5. Needle to lower looper timing
  6. Upper Looper Timing
  7. Chain looper timing (Safety Stitch)
  8. Upper Knife Adjustment
  9. Lower Knife adjustment
  10. Feed Dog height adjustment
  11. Cam Timing
  12. Thread Adjustment

Overlock machines can not 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.

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