Abstract: A device for focusing optical instruments, for example a telescope or microscope, includes a drive assembly having a fine and a coarse control knob. The knobs operatively connect with a drive shaft that extends transversely through a concave shaped support area of the drive. Seated in this support area is a tubular-shaped housing having an opening that fits over the drive shaft. Respective pairs of longitudinally spaced apart bearings then are attached to an inside wall of the housing to proximately align one each with ends of the housing shaft opening. A tubular-shaped drawtube then movably fits in the housing where a friction plate carried by a bottom portion of the drawtube engages the drive shaft. In an outer surface of the drawtube on each side of the friction plate is a longitudinal slot. Each slot has a bottom offset for a self-locating rail. Respective upper flat segments of the rails are in rolling contact with one each of the bearing pairs.