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Robbins Small Boring Unit breaks world record

Turn-Key Tunneling, Inc. completed a 352-foot (107m) bore length using a Robbins Small Boring Unit (SBU-A), setting a record for trenchless boring in the 54-inch (1.4m) diameter bore-size class. It also proved to be at least five times faster than hand mining in this case. The machine broke through just 0.17-inch (4.3mm) off of line and grade, and well within its contractual ± 3-inch (8cm) requirements.

The Robbins Small Boring Unit (SBU-A) is a type of trenchless boring attachment for use with standard Auger Boring Machines (ABMs). The SBU-A, with diameters from 24 to 72 inches (600mm to 1.8m), consists of a circular cutterhead mounted with disc cutters. The disc cutters are capable of excavating rock from 4,000 to over 25,000 psi (25 to over 175 MPa) UCS. In mixed ground, the cutterheads are fitted with a variety of tungsten carbide bits and single or multi-row disc cutters.

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29100 Hall Street
Solon, OH
US, 44139


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