| System | Function | How It Works on a Wertheim | |--------|----------|----------------------------| | | Engages/disengages needle movement | Pulling the handwheel out (or turning a knob) disengages the needle for bobbin winding. | | Needle Bar | Moves needle up/down | Driven by crankshaft from handwheel. | | Thread Take-Up Lever | Controls thread tension & pulls stitch tight | Moves in sync with needle – down as needle goes down, up as needle rises. | | Tension Discs | Controls upper thread tightness | Thread passes between two spring-loaded discs. Knob adjusts pressure. | | Bobbin & Case | Holds lower thread | Fits into shuttle hook under needle plate. Spring tension controls bobbin thread. | | Feed Dog Mechanism | Moves fabric | Eccentric cam under machine moves the feed dogs in a rectangle pattern. | | Stitch Length Regulator | Changes stitch length | Adjusts how far the feed dogs travel forward each cycle. | | Stitch Width (Zigzag models) | Moves needle side-to-side | A cam mechanism shifts the needle bar horizontally when you select a stitch pattern. |
Here is what happens mechanically when you turn the handwheel or press the foot pedal: máquina de coser wertheim como funciona