T38 89mm Retrac Button Bit for Rock Drilling

The T38 89mm retrac flat face dome button bit is a top hammer rock drilling tool engineered for bench drilling, production drilling and tunnelling in broken or fractured hard rock. Equipped with a retrac (retractable) skirt body featuring reverse cutting splines and a heavy-duty 13-button array, this 3.5-inch bit prevents rod jamming during retraction while delivering a long wear life under high impact.

Product Overview

The retrac body profile uses back-cutting edges on the bit skirt to crush loose rock and debris automatically during tool retrieval, eliminating stuck drill strings in fissured rock. Combined with 8 thick 13mm gauge buttons that prevent outer diameter shrinkage and 5 center 12mm buttons that accelerate central rock crushing, this bit maintains a full 89mm hole in demanding ground conditions.

Main Applications

• Bench Drilling: Open-pit quarry bench drilling in fractured, abrasive or fissured medium-to-hard rock.
• Production Drilling: Long-hole production drilling on modern hydraulic rigs.
• Underground Tunnelling: Drilling in broken or fractured rock where hole collapse is common.
• Fractured Rock Formations: The 89mm hole size provides efficient blasting hole fragmentation.

Key Features & Advantages

• Retrac Body Profile: Back-cutting edges on the bit skirt crush loose rock and debris during tool retrieval, preventing stuck drill strings in fissured rock.
• Button Dual-Diameter Layout: Eight 13mm gauge buttons prevent outer diameter shrinkage, while five 12mm center buttons accelerate central rock crushing.
• Dome / Spherical Carbide Profiles: Provide high impact resistance and reduce chipping or shearing under high percussive pressure.
• Flat Face Geometry: Ensures high drilling stability, smooth energy transfer and straight hole alignment in tough strata.
• Anti-Jamming Design: Significantly reduces the risk of stuck drill rods in fractured or sticky rock formations.

Product Specifications

FAQ

Q1: What is the main advantage of choosing a retrac skirt over a normal skirt on a T38 89mm bit?
A: The primary advantage is anti-jamming capability during drill string retraction. The retrac body features reverse-cutting splines on the back of the skirt that crush falling debris, loose rock or collapsing hole walls when pulling the bit back, significantly reducing the risk of stuck drill rods in fractured or sticky rock formations.

Q2: What rock drilling applications are most suitable for a T38 89mm retrac flat face button bit?
A: It is engineered for open-pit quarry bench drilling, long-hole production drilling and underground tunnelling in fractured, abrasive or fissured medium-to-hard rock. The combination of T38 threads and an 89mm hole size delivers efficient blasting hole fragmentation on modern hydraulic rigs.

Q3: Why does the bit use a dual-size button arrangement (13mm x 8 + 12mm x 5)?
A: This 13-button setup provides balanced stress distribution across the 89mm bit face: eight 13mm gauge buttons absorb severe peripheral abrasion and preserve the full hole diameter, while five 12mm center buttons crush the central rock core quickly and leave flushing space to clear cuttings.

Q4: How does a flat face profile benefit a retrac bit in hard rock drilling?
A: A flat face profile offers high structural rigidity and even impact force distribution across all 13 spherical buttons. Paired with a retrac body, it helps maintain good hole straightness and protects the bit face from uneven wear when drilling through changing rock layers.

Q5: How do dome (spherical) buttons improve tool life compared with ballistic buttons?
A: Dome buttons feature a rounded profile that distributes impact force uniformly, providing high resistance to carbide chipping, cracking and shearing under high-power top hammer impact. While ballistic buttons drill faster in soft non-abrasive rock, dome buttons offer a longer working life in hard, abrasive or fractured rock.