the component parts. The primary feature of each component is explained in the following text: Lifting Presser Bar Tension Regulating Screw. Regulates the pressure on the alternating presser foot. Feed Indicating Disc. Indicates the number of stitches per inch which are being made by the machine. Balance Wheel. Provides a connection between the driving unit and the sewing machine head. Arm-and-Hook Driving Shaft Connection Belt. Connects the upper arm shaft with the hook driving shaft. Feed Dog. Feeds the material from the under side. Rotary Hook Assembly. Contains the mechanism that forms the lockstitch by using the needle and bobbin threads. Bobbin. Contains the lower thread used in forming the lockstitch. Bobbin Case Retainer Hook Gib. Holds the bobbin case in the bobbin race. Needle-deflecting Hook Washer. Deflects the needle so the rotary hook will not strike the needle. Throat Plate. Surrounds the feed dog and keeps the material from slipping after the feed dog has been adjusted to the proper height. rotary plate. Bed Slides. Covers the feed eccentric and hook assembly on each side of the throat Feed Indicator Plunger. Used in connection with the feed indicator to regulate the number of stitches per inch desired. Safety-clutch Lock Stud. Re-engages the needle with the hook driving assembly after clearing a thread jam. Bobbin Case Opener. Prevents thread from jamming underneath the throat plate on the bobbin case base. 9-20 239.449 Figure 9-25A.—Class 111 sewing machine, side view. Rotary Hook Saddle Complete. The rotary hook is operated by the spiral driving pinion gear, which, in turn, is operated by the hook driving gear located on the hook driving shaft. Rotary Hook and Connection Belt Timing Plate and Arrows. Used to time the arm shaft with the hook driving shaft. The following parts are shown in the side view of the Class 111 sewing machine (figures 9-25A and 9-25 B). Thread Take-up Lever. Pulls the needle thread against the tension disc after the lockstitch is formed at the rotary hook and pulls suffi- cient thread from the spool to make the next stitch. Vibrating Presser Bar Tension Regulating Screw. Regulates the pressure on the presser foot. Only sufficient pressure to securely is needed. hold the material Face Plate. Covers mechanism of the two pressel and protects the feet and needle bar.