Abstract: A device for use in a button sewing machine which uses a wire of elastic material for maintaining looseness to that portion of the needle thread between a button and material to which the button is to be sewn while preventing the needle thread from being pulled out of the eye of the needle and at the same time preventing the wire from being warped.

Abstract: A speed controller for controlling revolution speed of the upper shaft of a cycle sewing machine comprises a first disk shaped stop lever adjustment cam that has a small diameter portion, middle diameter portions and a large diameter portion. The cam is rotatably driven by an upper shaft. The small diameter portion establishes a neutral position at which a first driving clutch for low speed rotation and a second driving clutch for high speed rotation are disengaged from each other. The middle portions establish a position at which the first clutch is connected to a first driving wheel for low speed rotation. The large diameter portion establishes a position at which the second clutch is connected to a second driving wheel for high speed rotation. A first end portion of the large diameter portion is defined by a second cam. The second cam is secured to the first cam by an adjustable device which can vary the circumferential position of the second cam.