Abstract: A pre-cast, reinforced concrete manhole riser is provided with a precisely aligned porthole for a sewer pipe, by cutting the hole on the site, the resulting smooth-faced, unobstructed porthole being sealed by a flexible collar having one end clamped on the pipe and having a flange at the other end adhered to the riser around the cut hole. Apparatus for cutting the hole, on the site, clamps on the upper rim of the riser, there being a cutter and carriage which move relative to a clamped frame.

Abstract: Precision ball bushings running on pecision shafts provide the basic movement and positioning for both the X and Y axes. For smooth precise operation there must be practically nil deflection of the shafts. To accomplish this, cam followers running on guide bars are provided to carry the load; the guide bars being supported along their entire length. The work bed, which can accommodate 4 .times. 8 foot plates, has replaceable nylon pieces screwed on to steel tubing of the frame assembly. Thus, when the drill penetrates the work, it usually encounters the air space, but if it strikes a nylon piece, there is no adverse affect on the operation, and the nylon may eventually be replaced.

Abstract: A frame structure supports a work surface above which there is provided an elongated head number supporting a series of drills. A torque tube having an axis parallel to and spaced from a line passing through the series of drills is mounted to the frame structure for rotation about its axis. The drill head member is coupled to the torque tube such that rotation of the torque tube initially swings the head member in an arc and thereafter urges the head member through a lost motion coupling arrangement against a pair of spaced parallel guide rails, secured to the frame structure normal to the work surface so that the remaining travel of the drill head is rectilinear. The stiffness of the torque tube assures that one end of the elongated drill head will not move ahead or drop behind the other end so that all holes are drilled simultaneously.