Description
The YYG90 Shank Adapter (also referred to as a striking bar) is the critical mechanical interface between a YYG-90 pneumatic rock drill drifter and the downstream drill string. Its primary role is to receive axial impact energy from the piston and transmit it — together with rotational torque — efficiently into the drill rod and bit without energy loss or structural compromise.
RockHound YYG90 adapters are produced through a tightly controlled manufacturing process that eliminates internal micro-stresses, ensuring consistent mechanical integrity from the first blow to the last. Designed for the most demanding underground mining, tunneling, and quarrying environments, they are a direct drop-in replacement for OEM YYG-90 striking bars.
For a detailed breakdown of shank adapter construction, see: What is a Shank Adapter — Structure and Function.
Material: 23CrNiMo Alloy Steel
Every RockHound YYG90 Shank Adapter is manufactured from 23CrNiMo alloy steel — the industry benchmark for high-impact rock drilling applications. This low-alloy, case-hardening steel delivers an optimal combination of:
- Surface hardness — resists abrasive wear and impact pitting on the striking face
- Core toughness — absorbs high-frequency piston blows without brittle fracture
- Fatigue resistance — sustains millions of impact cycles in continuous tunneling and mining operations
Compared to conventional grades, 23CrNiMo offers measurably superior performance under cyclic stress. See our full material comparison: 23CrNiMo vs. Sanbar64.
Features
- Premium 23CrNiMo Alloy Steel — High-strength base material selected for its proven balance of surface hardness and core ductility. Why 23CrNiMo outperforms Sanbar64 →
- 20-Hour Carburizing Heat Treatment — Each adapter undergoes a specialized long-cycle carburizing process that builds a deep, wear-resistant case while preserving a resilient, impact-absorbing core. Understand our heat treatment process →
- Precision R32 Threading — CNC-machined R32 male threads ensure accurate coupling geometry, minimal energy dissipation at the joint, and resistance to thread stripping under reverse torque.
- Dual Shank Length Options — Available in 330 mm and 380 mm to suit varying drifter chuck depths and drill string configurations.
- OEM-Grade Dimensional Accuracy — Manufactured to ±0.01 mm tolerances on critical surfaces (shank diameter Ø38 mm, collar Ø56 mm, pilot Ø32 mm) for seamless compatibility with standard YYG-90 drifters.
- Custom OEM/ODM Marking Supported — See branding section below.
Technical Specification
| Product Code | Model | Length L (mm) | Diameter D (mm) | Thread | Weight (kg) |
|---|---|---|---|---|---|
| 402-3833-5154 | YYG-90 | 330 | 38 | R32 | 2.7 |
| 402-3833-5164 | YYG-90 | 330 | 38 | R32 | 2.7 |
| 402-3838-5154 | YYG-90 | 380 | 38 | R32 | 2.8 |
| 402-3838-5164 | YYG-90 | 380 | 38 | R32 | 2.8 |
Key Dimensional Reference (YYG-90):
- Collar diameter: Ø56 mm
- Shank diameter: Ø38 mm
- Pilot (spline) diameter: Ø32 mm
- Chuck engagement length: 25.4 mm
Note: The suffix -5154 and -5164 denote flushing hole configurations (center flush vs. side flush). Confirm your drifter’s flushing system before ordering.
Applications
The YYG90 Shank Adapter series is engineered for high-duty pneumatic rotary guide rail rock drilling across:
- Underground Mining — Long-hole production drilling, cross-cutting, and development drifting in hard-rock mines
- Tunnel Construction — Face drilling, ring drilling, and systematic rock bolt installation
- Quarrying — Bench drilling for aggregate, dimension stone, and mineral extraction
- Civil & Infrastructure — Foundation drilling, shotcrete anchor installation, and hard-rock excavation in construction projects
How to Select the Right YYG90 Shank Adapter
Selecting the wrong shank adapter is one of the leading causes of premature drifter failure. Use the following criteria to match the correct YYG90 variant to your equipment:
1. Drifter Compatibility
Confirm your rock drill model is a YYG-90 or a directly compatible pneumatic drifter. Shank geometry (Ø38 mm diameter, 25.4 mm chuck engagement, Ø32 mm pilot) must match the drifter chuck specification exactly.
2. Thread Type — R32
All YYG90 adapters use R32 (rope thread) male ends. Verify your drill rods and coupling sleeves are also R32. Never mix thread forms (e.g., R32 with T38 or T45) — mismatched threads cause immediate thread stripping and risk piston damage.
3. Shank Length — 330 mm vs. 380 mm
- Choose 330 mm (L) for standard chuck depths and where weight savings are preferred.
- Choose 380 mm (L) when drilling geometry, guide support length, or drill feed configuration requires a longer striking bar.
4. Flushing Configuration — -5154 vs. -5164
- -5154: Center flushing — for drifters with axial water/air flushing through the drill string.
- -5164: Side flushing — for drifters with lateral flush port entry.
Confirm the flushing mode of your specific drifter model before ordering.
For a comprehensive selection guide, refer to: Shank Adapter: Function, How It Works, Selection & Maintenance
How to Maintain the YYG90 Shank Adapter
Proper maintenance directly extends service life and protects your drifter from secondary damage. Follow these field-proven protocols:
1. Thread Lubrication (Before Every Shift)
Apply a high-quality, EP-grade thread grease to the R32 male threads before coupling. Dry or contaminated threads accelerate galling and micro-welding, leading to premature thread failure.
2. Striking Face Inspection (Daily)
Inspect the rear striking face for signs of pitting, indentation, or cracking. A concave wear depth exceeding 2 mm indicates the adapter has reached end-of-life and must be replaced immediately to prevent piston damage.
3. Shank Surface Check (Weekly)
Examine the chuck engagement zone (Ø38 mm shank body) for transverse cracking or spalling. Surface cracks perpendicular to the drill axis are a fatigue indicator — remove the adapter from service without delay.
4. Alignment Verification
Ensure the shank adapter, drill rod, and bit are coaxially aligned within the feed guide before drilling. Off-axis loading creates bending stress, which dramatically shortens fatigue life.
5. Flushing Integrity
Check flushing holes for blockage at each rod change. Restricted flushing causes overheating at the striking face, accelerating wear and thermal cracking.
6. Torque at Coupling
Tighten to the drifter manufacturer’s specified coupling torque. Under-torqued connections cause fretting and micro-slip; over-torqued connections risk thread stripping.
Full maintenance protocols are available in our guide: Shank Adapter: Function, Work, Choose & Maintenance
Custom Branding & OEM Marking
RockHound supports full OEM and ODM branding on YYG90 Shank Adapters for distributors and equipment manufacturers:
- Marking Method: Laser etching or mechanical stamping
- Maximum Logo Size: 100 × 100 mm
- Placement: Applied exclusively to the non-impact, non-contact surface of the adapter body to preserve structural integrity and heat-treatment case depth
- Minimum Order Quantity: Contact us for branded order thresholds
Custom packaging, part number labeling, and private-label certification documentation are also available upon request.
Related Production
- R32 Coupling Sleeves
FAQ
The YYG90 Shank Adapter acts as the primary energy transfer component between the drill's reciprocating piston and the drill string. It converts linear piston impact into longitudinal stress waves transmitted down the drill rod, while simultaneously transferring rotation torque to advance the bit. Its design and material integrity directly determine overall drilling efficiency and drifter longevity. Learn more about shank adapter structure and function →
23CrNiMo is a low-alloy, case-hardening steel that responds exceptionally well to carburizing heat treatment. After the 20-hour carburizing cycle, the surface achieves a hardness of approximately 58–62 HRC for wear resistance, while the core remains at 38–42 HRC for toughness — a combination that no standard carbon steel or lower-alloy grade can replicate under the cyclic impact loads of rock drilling. Full material analysis: 23CrNiMo vs. Sanbar64 →
R32, T38, and T45 are standardized rope-thread profiles used on drill rods and shank adapters. They differ in thread major diameter, pitch, and taper — and are not interchangeable. The YYG90 uses R32, which is suited for lighter pneumatic drifters and smaller hole diameters (33–51 mm). T38 and T45 are used with heavier hydraulic drills for larger-diameter applications. Always match the adapter thread to the drill rod thread — mismatches will destroy both components within seconds.
These suffixes designate the flushing hole configuration of the adapter. The -5154 variant features a center flush channel, where water or air travels axially through the drill string. The -5164 variant uses a side flush port, with fluid entering laterally from the drifter housing. Selecting the wrong flushing type will result in inadequate cuttings removal and rapid bit wear.
Key replacement indicators include:
- Striking face pitting or concave wear depth exceeding 2 mm;
- Visible transverse cracks on the shank body or collar;
- Thread wear showing thinning flanks or signs of galling;
- Abnormal vibration or energy loss at the drifter — often the first sign of internal fatigue cracking.
Replacing the adapter at the first sign of these conditions prevents cascading damage to the drifter's piston and chuck bushing.