Abstract: A compact and portable coil inserting machine for binding stacks of sheets having a plurality of perforations along a first side edge. The machine includes a frame having a support surface configured to support a stack of sheets thereon. A power roller is rotatably mounted to the frame, and extends along at least a portion of the support surface to drive a helical coil through the perforations in the stacked sheets. The coil-inserting machine further includes at least one guide that is movably mounted to the frame, and shifts between first and second positions. The guide includes a first concave guide surface that abuts an opposite side edge of the stacked sheets when the guide is in the first position, such that the perforations in the stacked sheets form a curved passageway corresponding to the curvature of a first coil size.