Description
T38 76mm Retrac Button Bits are purpose-built for top hammer bench drilling, long-hole production drilling, and open-pit quarrying in medium-to-hard rock formations. The retrac (retraction) design — featuring peripheral back-reaming cutters on the skirt — prevents the bit from getting stuck in fractured or caving ground, dramatically reducing rod-pull resistance and improving overall footage per shift.
Available in Flat Face and Drop Center profiles, each variant is manufactured with a 45CrNiMoVa alloy steel body and YK05 tungsten carbide inserts to deliver the optimal balance of fatigue resistance and abrasion wear life.
Discover: Rock Drill Bits Manufacturing Process
Key Features
Retrac Skirt for Anti-Jamming Performance
The back-reaming profile on the gauge shoulder reams the hole wall during retraction, keeping the drill string free in broken, fractured, or swelling ground conditions — a critical advantage in bench drilling applications where hole collapse is common.
45CrNiMoVa Alloy Steel Body
The high-alloy steel provides superior fatigue strength and toughness under repeated high-frequency percussive impact, extending body service life before washing or cracking occurs.
YK05 Tungsten Carbide Grade
YK05 is a medium-grade carbide with a cobalt content optimized for a blend of wear resistance and impact toughness — the industry-proven choice for hard and abrasive formations including granite, basalt, and quartzite.
T38 Thread Interface
The T38 male thread ensures full-face contact and efficient shock energy transfer from the drill rod to the bit face, minimizing thread wear and reducing the risk of uncoupling.
Multi-Port Flushing Design
Strategically positioned flushing holes maintain high air or water velocity across the bit face to evacuate cuttings rapidly, prevent regrinding, and control bit temperature.
Technical Specifications
All specifications below are for the 76 mm (3 inch) diameter, T38 thread, Retrac body design.
Face Type 1: Button / Flat Face / Retrac
Flat Face provides maximum contact area and sheer button support, making it the preferred choice for very hard, competent, and highly abrasive rock where button breakage is the primary failure mode.
Face Type 2: Button / Drop Center / Retrac
Drop Center (concave face) concentrates initial percussive energy at the centre of the hole bottom, improving penetration rate in medium-hard, fractured, or laminated rock and providing better hole-straightness control.
Face Design Selection Guide
| Rock Condition | Recommended Face | Reason |
|---|---|---|
| Very hard, massive, abrasive (e.g. granite, quartzite) | Flat Face | Greater button support area; significantly reduces risk of button fracture and chipping under extreme high-impact loading |
| Medium-hard, fissured, or interbedded | Drop Center | Faster initial penetration and self-centering action; effectively reduces hole deviation and deviation in layered or fractured zones |
| Fractured or caving ground (all types) | Either + Retrac Skirt | Retrac skirt prevents bit jamming and loss regardless of face profile; essential for unstable or collapsing formations |
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Applications
Open-Pit Bench Drilling – The 76 mm diameter and T38 thread deliver the hole size and energy transfer needed for standard blast-hole patterns in open-pit mining. The retrac design is particularly valuable in benches with weathered or jointed overburden.
Underground Long-Hole Stoping – In sub-level stoping and long-hole blasting, maintaining hole straightness over depths exceeding 20 m is critical. The T38-76mm Retrac bit works in tandem with T38 extension rods to achieve low deviation rates across the full drill length.
Quarrying & Dimension Stone – Consistent 76 mm hole diameter, maintained through the life of the bit by the gauge buttons and retrac profile, ensures uniform burden and spacing distances — directly reducing explosive consumption per tonne.
Construction & Infrastructure – Suitable for pre-splitting, controlled blasting, and foundation drilling in hard rock terrain where borehole integrity is a project requirement.
Compatible Drill String Components
To achieve optimum performance, pair your T38-76mm Retrac Button Bit with:
T38 Extension Drill Rods
R32/T38 conversion available for deeper hole applications
T38 Male/Female Couplings
for extending drill string in long-hole configurations
T38 Top Hammer Shank Adapters
compatible with Atlas Copco, Sandvik, and equivalent top-hammer rock drills
Maintenance Guidelines
1. Regrinding Trigger Point
Regrind carbide buttons when the wear flat reaches approximately 1/3 of the button diameter. Delaying regrinding beyond this point accelerates button shattering and steel body washing, significantly shortening bit life.
2. Thread Lubrication
Apply dedicated thread grease (MoS₂-based compound recommended) to the T38 thread before every shift. This prevents galling, reduces uncoupling torque, and avoids thread seizure — a leading cause of premature bit retirement.
3. Flushing Pressure Check
Verify that air or water flush pressure and volume are within the drill rig manufacturer’s specification. Insufficient flushing is the primary driver of accelerated bit face wear through cuttings regrinding.Lorem ipsum dolor sit amet, consectetur adipiscing elit. Ut elit tellus, luctus nec ullamcorper mattis, pulvinar dapibus leo.
4. Storage
Store bits in a dry, covered environment to prevent rust on the 45CrNiMoVa steel body. Stack horizontally on padded racks to avoid button chipping from contact impact.
View: Top Hammer Button Bit: How It Works, Uses & Maintenance
Order Information
All T38-76mm Retrac Button Bits: Thread T38 · Diameter 76 mm (3 in) · Gauge 8×11 mm · Centre 6×10 mm · Body 45CrNiMoVa · Carbide YK05
Looking for other thread sizes or diameters? We also supply T38 button bits in 64mm and 70mm, as well as R32, T45, and T51 series. Contact us for custom configurations and OEM bulk pricing.
Frequently Asked Questions
The T38 shank thread is the industry benchmark for 76–89 mm hole diameters in top-hammer drilling. Its larger thread profile (vs. R38 or T32) provides:
- Higher bending moment resistance, reducing lateral fatigue cracking at the shank
- Lower stress concentration at thread roots under axial percussive loading
- Broader compatibility with tier-1 and OEM top-hammer drill rigs
button bits have a plain cylindrical or tapered skirt. Retrac bits have a back-reaming shoulder with small cutting edges on the gauge area. When the drill string is retracted, these edges ream the hole wall, reducing pull-out force and preventing the bit from getting jammed — critical in broken or collapsing ground.
YK05 is optimized for medium-to-hard rock with a UCS (Uniaxial Compressive Strength) range of approximately 100–250 MPa (e.g., limestone, diorite, granite). For softer and more abrasive siliceous rock, a higher cobalt grade may be considered.
Yes. T38 76mm Retrac Button Bits can be reground multiple times using button bit grinding machines (e.g., Grind Matic or equivalent). A proper regrinding program can extend total bit life by 30–50%.
The flat face variants weigh 3.3 kg (35° gauge angle) and 2.4 kg (40° gauge angle). The drop center variants weigh 2.7 kg and 2.5 kg respectively. Weight differences are attributable to differences in face geometry and body material distribution.