A sewing machine having two needles supported in a needle holder, which needle holder is horizontally displacable, to present one needle to an active workstation in a prethreaded manner and simultaneously shift the other needle which has a different thread therein, into an adjacent inactive position. As the needles are being shifted, the needle moving to inactive status has its thread clamped against the needle holder by a wheel, to secure the thread from being pulled therefrom or straying. A vacuum tube arranged at each respective inactive position or station sucks the tail of the thread therein. A pair of thread guides, one for each thread, are arranged for vertical movement, to pullback on the dangling thread of the inactive needle, to prevent the thread from whipping during its inactive status. Each thread passes around a thread engaging wheel comprising a dual bobbin monitor arranged on a single axis. A thrust bearing is arranged between each thread engaging wheel and an adjustable knob is arranged to bias the sides of the wheels to allow each thread to have the same tension regardless of its current status, active or inactive. A wedge arrangement at the drive end of the sewing machine mates into a groove on a disk attached to the drive shaft which wedge arrangement, after stopping the drive shaft from rotating, then permits the shifting of the needles from active to inactive status. The wedge mating in the groove of the shaft insures proper alignment of the shifting mechanism permitting the shuttling of the needles from their inactive to the active position and vice versa.