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Read paired barrel diameters, distinguish upper stabilizers from lower guides, and identify the existing bore before discussing a staged enlargement tool.

Learn how a core-barrel scraper addresses residual rock and guides loose fragments outward, and why scraper height and fines removal are separate questions.

Understand nominal 8½-inch roller-bit size, the MH-3 catalogue cone size and the separate mounting and cutting dimensions that determine replacement fit.

Original field and section photographs show where to examine a trench cutter tooth holder before replacement, and how to separate fit checks from material testing.

A useful material file links the steel grade to the cone or leg, then to treatment and finished-part records. The component identity comes before the test numbers.

Hand rotation checks movement; it does not measure bearing fit. Inspect the journal, mating bores, seal seat and assembled movement against the selected drawing.

Original photographs, a 22.5 m inspection annotation and an insert section show how supporting steel, cutter placement and entry behaviour were reviewed together.

MH-3 field experience: approximately 35–50 m in 100–150 MPa granite. Read the Zengcheng drilling and wear record, then calculate cutter cost per metre for your own job.

A ten-position site inspection shows how to plan selected roller-bit replacements, review the surrounding barrel and identify the mounting and parts to order.

Recognise crystals, grains, shells, layering and weathering before choosing a drilling tool. Real reference photos explain the clues and their limits.