R25 75mm Threaded Button Bit Dome Tungsten Carbide Reaming Hard Rock Drilling

R25 75mm Threaded Button Bit for Rock Drilling

The R25 75mm dome threaded button bit is a top hammer rock drilling tool engineered for large-hole drilling, cut-hole opening, reaming and heavy underground tunnelling in hard to highly abrasive rock. Featuring a normal skirt profile and a heavy-duty 12-button array, this 3-inch (75mm) rock bit delivers efficient impact energy distribution, high structural resistance to carbide pop-outs and a long wear life under intense percussive drilling.

Product Overview

Built entirely with thick 12mm tungsten carbide buttons (8 outer gauge + 4 center), the R25 75mm bit sustains severe impact and high abrasion during large-hole opening. The dome (spherical) button profile distributes percussion stress evenly, preventing button chipping and shearing in hard rock, while the precision-machined 42CrMo body with specialized heat treatment ensures long fatigue resistance across the R25 thread connection.

Main Applications

• Reaming: Enlarging pilot holes in hard rock tunnelling with standard R25 top hammer drill rods.
• Cut-Hole Opening: Large-diameter opening for underground tunnel blasting.
• Cable Bolting: Reliable drilling for cable bolt and roof support installation in mining.
• Bench Drilling: Production drilling in open-pit or underground mining operations.

Key Features & Advantages

• Heavy-Duty 12-Button Carbide Setup: Eight 12mm outer gauge buttons prevent rapid diameter loss and maintain the full 75mm gauge, while four 12mm center buttons break down central rock cores without clogging.
• Dome / Spherical Profile: Offers high fracture resistance under high-impact energy, preventing button chipping and shearing in hard rock.
• Heat-Treated Forged Alloy Steel: Precision-machined 42CrMo body with specialized heat treatment ensures long fatigue resistance across the R25 thread connection.
• Optimized Flushing Capacity: Multi-hole flushing channels quickly clear heavy rock cuttings and reduce re-grinding.
• Thick 12mm Carbide: Provides higher shearing and impact resistance than smaller 9mm or 10mm buttons under heavy loads.

Product Specifications

FAQ

Q1: What are the primary applications for an R25 75mm dome threaded button bit?
A: It is primarily used for reaming (enlarging pilot holes), cut-hole opening in underground tunnel blasting, cable bolting and bench drilling in medium-to-hard rock. Operating at a 3-inch (75mm) diameter, it serves as an efficient large-diameter reaming tool paired with standard R25 top hammer drill rods.

Q2: Why is the 12-button 12mm layout critical for a 75mm bit?
A: Drilling a 75mm hole on an R25 drill string subjects the bit face to high torque and percussion forces. Eight thick 12mm gauge buttons prevent rapid diameter loss so the bit maintains its 75mm gauge, four heavy center buttons break down central rock cores during reaming without clogging, and the 12mm carbide thickness offers higher shearing and impact resistance than smaller buttons under heavy loads.

Q3: How do dome (spherical) buttons compare with ballistic buttons on a 75mm R25 bit?
A: Dome buttons are recommended for hard, highly abrasive or fractured rock, as their rounded geometry distributes percussion stress evenly and offers high fracture resistance with stable wear growth. Ballistic buttons penetrate faster in soft, non-abrasive rock but carry a higher risk of chipping or shearing when driving a large 75mm bit into hard or fractured rock.

Q4: Can an R25 75mm bit be used for direct single-pass drilling, or is it mainly for reaming?
A: It can be used for direct drilling in soft to medium rock formations, but it is most commonly used as a reaming bit in hard rock tunnelling. Reaming a pre-drilled 35-45mm pilot hole reduces energy loss, minimizes hole deviation and protects the drill string from excess bending stress.

Q5: How can operators extend the service life of an R25 75mm heavy-duty rock bit?
A: Regrind buttons when flat wear spots reach one-third of the 12mm button diameter, maintain high-pressure flushing to purge large rock cuttings instantly, and keep steady feed pressure to avoid collar bouncing that can damage carbides, while avoiding excessive rotation speed that accelerates gauge wear.