Bobbin The Bobbin in a sewing machine contains the thread that makes the bottom of a stitch. Bobbins are wound with a type and color of thread appropriate for the your project. The Bobbin is placed in a cylindrical housing called a Bobbin Case or Bobbin Shuttle (Photos 11, 12 & 13). The Bobbin Case includes a thin metal band with a small screw to adjust the tension of the thread coming out of the Case. Bobbins can be oriented with the thread exiting the Case in the direction of the adjuster band or flipped over to exit the band opposite to provide a greater range of tension.
Photo 11 A partially used bobbin removed from the bobbin case. The case is essentially a shell that holds the bobbin, allowing it to spin freely.
Photo 12 A fully wound bobbin inserted in a bobbin case and the thread is routed counter clockwise (left) first into the slanted slot and then under the metal tab as shown. The metal tab provides extra tension on the thread as it is released from the bobbin case. This tension can be adjusted by a small slotted screw just out of view in this photo. Once set, it almost never requires adjusting. When inserting back into the machine, leave a tail of 3-4 inches.
Photo 13 View of the machine head tilted back onto the table showing the bobbin case. The thin lever in the middle of the bobbin case is a locking clasp. It is folded back whenever removing or inserting the bobbin & case.
Reversing Lever A Reversing Lever or Control (Photo 14) is used to temporarily reverse the direction of the stitch. You cannot perform a reverse stitch by turning the Hand wheel backwards. The reverse is used to make lock stitches and only operates in reverse while pressed down. When not pressed down the machine will automatically run in its normal forward-sewing operation.
Photo 14 The horizontal lever on the right side of the machine is the reversing bar. Not all sewing machines include this feature, but is somewhat common on commercial machines such as this JUKI.
Presser and Needle Foot The Presser Foot (Photo 15) is sometimes confused as being the entire assembly on the left side of the machine over the shuttle cover where the needle passes into the Feed Dog (see Feed Dog below). The two feet are two different components; the Needle Foot (that the needle passes through) and the rest of the Presser Foot. They operate independently of each other. Each foot can have different shapes and configurations depending on the task at hand. A piping foot is quite different than a zipper foot and that is different than a regular foot.
Photo 15 Shown is a close up view of the Presser Bar Foot (left and right of the Needle Foot), the Needle Foot in the middle (easily recognized with the needle running through it), and the Needle itself. Note the Needle Foot is free to move independently (up and down and front and back) of the Presser Foot. Coming through a slot in the bottom plate is the Feed Dog, the serrated teeth that pull the material through the machine as the stitches are formed. With each stitch, the Feed Dog lowers, moves forward, raises and pulls the material forward so that the next stitch can be made. This is the main motion which gives this machine its name, a Compound Walking Foot. The thread is routed down the left side of the needle and note the groove in the side of the needle. Its this groove that the thread with travel in while the needle pierces the fabric to make a stitch.