SBU DIVISION Metric Version SMALL BORING UNIT (SBU-A) The Small Boring Unit (SBU-A) is a proven solution for medium to hard rock utility installations up to 150 m in length. The SBU-A can be used with any conventional auger boring machine (ABM) from 0.6 to 1.8 m in diameter and utilizes a full-face auger for spoils removal. Before excavation, the SBU-A is welded to the lead casing. A full-face auger is added to the casing and the assembly is lowered onto the ABM track. In hard rock, the circular cutterhead is fitted with disc cutters, while in mixed ground a combination of ripper teeth, drag, bits, and disc cutters are used. SBU-A APPLICATIONS • Full-face auger boring • Replacement for carbide bit and roller cone cutterheads • Bore lengths up to 150 m [depending on geology] CUTTING THROUGH ROCK Small Boring Units utilize disc cutters from 165 mm to 356 mm in diameter to excavate rock. Disc cutters penetrate the rock face and create a “crush zone” through which fractures propagate. Material between adjacent crush zones is then chipped from the face. Muck scrapers scoop the muck into openings on the cutterhead (called muck buckets), which transfer the material to a fullface auger for removal. IMPROVED BORING EFFICIENCY Unlike typical carbide bit or roller cone cutting heads, the SBU-A can power through rock over 175 MPa UCS. Most tungsten carbide cutting tools tend to break off in rock above 50 MPa UCS, requiring expensive replacements and machine downtime. A COST EFFECTIVE SOLUTION The SBU-A has been successfully used on hundreds of projects around the world to efficiently excavate hard rock. By maximizing machine availability and minimizing labor costs, a typical SBU-A/ABM setup is economically better than carbide bit or roller cone cutting heads.

SMALL BORING UNIT (SBU-A) SIDE VIEW Disc Cutter FRONT VIEW MACHINE DIAMETERS ROCK STRENGTHS GROUND CONDITIONS Cutter Size - 165, 241, or 292 mm Torque Req - 51,800 to 69,000 N-m Medium to hard rock, or mixed ground Thrust Req - 830 to 1,560 kN Machine Length - 1,265 mm Weight - 5.56 to 6.62 metric tons Weight - 0.861 metric tons Weight - 1.54 to 1.61 metric tons Weight - 3.04 to 3.72 metric tons Weight - 7.71 to 8.07 metric tons Weight - 1.12 metric tons Weight - 1.72 to 2.25 metric tons Weight - 3.38 to 4.29 metric tons Weight - 7.94 to 8.26 metric tons CORPORATE HEADQUARTERS The Robbins Company...