Machine Terminology:
The parts of the lockstitch machine, which are identified here, are illustrated in Figures 1.
• Arm: The horizontal part of the head that houses the drive shafts.
• Bed: The working surface of the machine un- der which is located the mechanism that han- dles the lower thread. On a flat-bed machine, the bed rests in the cutout of the table.
• Belt (motor belt or machine belt): The circular strap that transmits motion from the pulley to the handwheel, allowing the machine to operate.
• Bobbin mechanism: The parts—bobbin, bobbin case, and bobbin tension spring—that control the lower thread and its tension.
• Bobbin winder: The part that fills a bobbin while the machine is stitching.
• Check spring (tension spring or take-up spring): A small wire spring behind or at the top of the tension discs. It provides a small amount of tension on the needle thread and acts as a shock absorber. On some machines, the check spring is mounted separately.
• Faceplate: The cover on the left side of the head that covers the needle bar and the presser bar.
• Feed dogs (feeder or feed): The toothed mecha- nism beneath the presser foot that moves the fabric forward and backward.
• Fittings: The parts—presser foot, feed dogs, and throat plate—that control the cloth dur- ing stitching.
• Handwheel (balance or flywheel): The part that controls the motion of the machine manually and/or electrically.
• Head: The part of the machine above the table, containing the stitching mechanism.
• Heel: The back of the presser foot.
• Hook (rotary hook or machine hook): A rotating device that hooks the needle thread to carry it around the bobbin and form the “lock” on the lockstitch.
• Knee lift (knee lifter or knee press): A lever mounted at the right under the sewing table to lift and lower the presser foot with the right knee.
• Motor: The electrical unit that drives the machine.
• Needle: The part that penetrates the fabric. It carries the thread to the hook or shuttle and up again to make the stitch.
• Needle bar: A vertical bar that holds one or more needles and moves the needles up and down.
• Needle screw (needle bar clamp): The screw that holds the needle in the needle bar.
• Oil gauge: The part that indicates the amount of oil in self-oiling machines.
• Pan (machine pan): The metal pan under the head that catches oil, lint, and metal shards. On self-lubricating machines, it holds the oil.
• Presser bar: The bar to which the presser foot is attached.
• Presser bar lifter: A lever at the back of the presser bar used to raise and lower the presser foot by hand. It is used to raise the presser foot when winding a bobbin and when not stitch- ing. (Its use is discouraged in industrial sewing because it wastes time and energy.)
• Presser foot: A device that holds the fabric in place for stitching.
• Pressure regulator (pressure dial): Control that regulates the amount of pressure on the presser foot.
• Pretensioner: A simple tension disc used to regu- late the thread so that it will feed into the ten- sion assembly evenly.
• Pulley: The wheel attached to the motor. It transmits motion from the motor to the hand- wheel by means of a leather belt.
• Rotary hook assembly: The part that holds the bobbin case.
• Shuttle: An oscillating device that carries the needle thread around the bobbin and forms the “lock’’ on the lockstitch. The shuttle and the hook perform the same function—making a stitch—but the hook rotates and the shuttle oscillates.
• Slack thread regulator: A metal hook or bar near the tension discs.
• Slide plate (slide or bed slide): A removable cover at the left of the machine bed that allows ac- cess to the lower mechanism.
• Sole (shoe or slipper): The bottom part of the presser foot that contacts the cloth.
• Stand: A metal structure on which the table is mounted.
• Stitch hole (needle hole): The hole in the throat plate. The needle carries the thread into the hole so that it can interlock with the bobbin thread.
• Stitch regulator: A device that regulates stitch length.
• Switch (power switch): A key or button that turns the machine on and off.
• Table: The cabinet on which the head rests. It generally has a drawer on the left side.
• Take-up lever: The part that first loosens the top thread during the stitch formation, then re- moves any slack to set or lock the stitch.
• Take-up lever guard: A piece of metal in front of the thread take-up lever.
• Tension discs (tension springs): Two concave discs that control the delivery of the upper thread from the spool to the needle.
• Thread guides (thread eyelets): The parts that guide the thread from the thread cone to the needle. They smooth the thread and protect it from abrasion.
• Thread retainer (pretensioner): A three-hole guide that applies a small amount of tension on the thread so that it flows into the tension discs uniformly.
• Thread stand: A metal device that holds thread cones.
• Throat plate: The smooth surface directly under the presser foot that includes the stitch hole and surrounds the feed dog. It protects the lower mechanism from a buildup of excess lint.
• Toes (prongs): The front end of the presser foot, or the part that faces the oncoming cloth. It is frequently upturned. Feet such as the zipper foot, cording foot, and shirring foot have only one toe.
• Treadle (foot treadle): A metal platform on which the feet rest.
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