Abstract: A mortising machine adapted for connection to a conventional electric motor includes a frame having rotatably mounted therein a helically-grooved shaft on which is threadedly mounted a router assembly carrying a rotatable router bit for reciprocation along the grooved shaft upon its rotation. The shaft of the router bit and the grooved shaft are both driven from a drive shaft journaled in the frame by a drive connection arrangement of pulleys and timing belts to simultaneously rotate and reciprocate the router bit for cutting a linear mortised slot. For driving the shaft of the router bit, the drive arrangement includes a pulley on each of the drive shaft and router bit shaft, a traveling idler pulley mounted on an arm pivoted on the router assembly, and a timing belt trained about the pulleys.