Abstract: The hole-opener is designed so that it can be disassembled in the field to replace worn cones or to enlarge the effective diameter of the tool. It comprises: a tubular drive sub, which connects at its front end with a rotating drill string which is being pulled along a pilot hole; a sleeve which slides over the rear portion of the drive sub; and a retainer sub which is connected with the rear end of the drive sub. The drive sub has external protruding bars which engage slots formed in the forward end of the sleeve, for limiting forward movement of the sleeve and locking the drive sub and sleeve together so that they rotate as a unit. The retainer sub has a radial shoulder which abuts the rear end of the sleeve to lock it in place. The retainer sub also transmits axial pull from the drive sub to the sleeve. The sleeve carries rotary cutting elements which are pulled and rotated to cut formation and enlarge the pilot hole.