ROBBINS

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 t t
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.