... semi-rotary large capacity shuttle hook, suitable for sewing heavy weight materials. Used for harness, tack, saddlery, canvas ... frequency of changing the bobbin thread a built in bobbin winder, which can be reached with ease ... during sewing.The machine incorporates a built in bobbin winder, which can be reached with ease ... -Arm, Cylinder-Bed, Unison-Feed, Extra Heavy Duty, Lockstitch Sewing Machine