Principle of Lock Stitch Formation Techniques
Rahat Khan
Dept. of Apparel Manufacturing
Atish Dipankar University of Science and Technology
Email: rahat.info@gmail.com
Lock stitch formation
Lock stitch formation is very important for stitching mechanism. Stitch class-300 is called lock stitch. It can be formed by the interlacing of two or more threads. One group of thread is passed through the fabric and interlaced with another group of thread and formed lock stitch. One set of thread is called is needle thread and another set of thread is called bobbin thread.
The first stage in making a stitch is the formation of a loop from the needle thread. If the needle thread loops are not formed properly, then it leads to several stitching problems like skipped stitches, breakage of sewing thread, loose stitches, etc. Proper loop formation of the needle thread depends on the propensity of the needle thread to bulge away from the needle due to inertia and friction against the fabric as it is pulled in an upward direction subsequent to reaching the lowest point of its stroke. The second stage is receiving the top needle thread to go around the bobbin. This is accomplished using a bobbin hook coming across at the precise time and catching the top needle thread and drawing it around the bobbin. The principle of lock stitch formation can be illustrated as below-
The steps of a stitch: Put the picture for each step before the corresponding explanation.
The five steps of a lock stitch formation:
Step 1: Needle penetrates the fabric to bring top thread into bobbin area.
Step 2: The needle begins to lift and as the needle rises, top thread forms a loop for shuttle hook to catch.
Step 3: Shuttle hook carries the thread loop around and under the bobbin case.
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Step 4: Loop slides off hook and bobbin case, goes around bobbin thread.
Step 5: The threads are pulled up and are set into the fabric as a lock stitch.
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