Stitch Formation

       
     
.........................      
     

      The first step in producing a stitch on a sewing machine is the formation of the needle thread loop. This step is the same regardless of the type of stitching being produced, or the nature of the machine being used. Failure to generate a good loop will cause many different problems such as skipping, breaking thread, loose stitches, threading bunching up, etc...

Proper formation of this loop depends on the tendency of the thread to bulge away from the needle as it is drawn upward after reaching the lowest point of it's stroke - due to inertia and friction against the material through which it passes. 

 

 
     
 

 
     
 

 
         
 

 

     
 

 
     
 

 
     
     
     
     
     
     
     
     
     
     
     
      Any interference with the formation of the needle thread loop will result in faulty stitch formation. One of the most common conditions is that the material stitched is not held firmly by the presser foot at the point where the needle passes through, allowing the material to flag, or move up with the needle as it rises. Either no loop is formed at all, or the loop is formed too late. This will result in skipped or broken stitches. You should always refer to the needle, fabric and thread chart to make sure the right size needle is being used. A quick visual inspection of the foot and throat plate is also recommended.
     
     
     
     
     
     
     

     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
      The thread tends to form an equal loop on each side of the needle, a guard is used to push the loop through to the side from which the thread is taken by the shuttle, hook or looper.  Correct setting of this guard is necessary for good loop formation.
     
     
     
     
     

Step Two is getting the top thread to go round the bobbin. This is done by the hook coming across at the right time and catching the top thread and pulling it around the bobbin case and bobbin. This process is shown in figure 1 & 2. Figure 1 is without the hook, bobbin case and fabric. Figure 2 is with the hook, bobbin case and fabric.

     
     
     
     
     
     

     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
         

   
     

     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
      Knowing how a stitch is formed is very important! Especially when problems occur. The diagrams above can help you to visually watch a stitch being formed on your machine and teach you to watch for certain problems when sewing. Remember the top thread has to go completely around the bobbin case, in a smooth motion every time. to make a good stitch. If it gets stuck or even hesitate a little, this can result in the usual problems of skipping, breaking thread, loose stitches, thread bunching up etc...
     
     
     
     
     
      ....