HQ Heavy Duty Wireline Drill Rod for Underground Metal Ore Exploration | CGE Drilling

HQ Overshot Assembly is a vertical hole wireline core overshot of Q series, manufactured in strict accordance with international DCDMA standards. It is matched with HQ wireline drill rods and double-tube inner tube assemblies, acting as the core supporting tool for medium & large borehole diamond wireline core drilling. It features large fishing load and strong bearing capacity with big core diameter, suitable for deep and ultra-deep exploration holes, and serves as the main drill accessory for deep mineral and geothermal investigation.

Application Classification
Q series overshots (BQ/NQ/HQ/PQ) are designed for vertical boreholes and downward inclined holes with 35°~90° inclination. QU series overshots shall be adopted for horizontal or low-inclination tunnel holes of 0°~35°. The two series are designed for different working conditions and cannot be used interchangeably.
As a mainstream medium-large size of Q series, HQ overshot delivers a core diameter of 63.5 mm, featuring large single-run core recovery and excellent drilling stability. It fits medium-deep to ultra-deep exploration boreholes with a regular maximum working depth of 2000–2800 m, widely applied in deep metal mineral exploration, geothermal investigation and large infrastructure survey projects.

The full set of HQ overshot consists of 12 core components from top to bottom, complying with international DCDMA standards and featuring high interchangeability with standardized accessories:
1. Eye Bolt: Connects wireline winch and bears heavy lifting load. Forged thickened structure with strong tensile resistance and deformation resistance.
2. Swivel Assembly: Equipped with heavy-duty thrust bearings and long-lasting grease fittings. It rotates freely during lowering and lifting to prevent wireline twisting and wire breakage.
3. Jar Tube & Jar Rod Assembly: Extended jarring stroke provides powerful jarring force to quickly release deep-hole tube sticking, severe core blockage and inner tube adsorption jamming.
4. Lock Spring Sleeve & Lock Bushing: Thickened multi-stage locking structure limits the stroke of lifting dogs, ensuring the dogs stay locked under heavy deep-hole lifting load and preventing inner tube dropping accidents.
5. Main Compression Spring & Dog Spring: Thickened high-strength springs with stable rebound performance, accurately controlling opening, closing and automatic reset of lifting dogs without failure under heavy load.
6. Ball Position Indicator Mechanism: Obvious water pressure fluctuation occurs once the inner tube is fully latched, allowing surface operators to clearly confirm fishing status and avoid time-consuming empty fishing in deep holes.
7. Overshot Body & Lifting Dogs: Widened and thickened double lifting dogs with larger contact area, high load capacity, anti-slip and anti-unhooking performance when lifting heavy inner tubes in deep holes.
8. Positioning Pins & Spring Pins: Thickened pins fix the dog assembly for easy disassembly and rapid replacement of wearing parts on site.
9. Centralizing Guide Section: Widened large-diameter guide ensures perfect centering inside drill rods and high coaxiality, precisely aligning with inner tube spear head and improving one-time fishing success rate in deep holes.
10. Buffer & Shock Absorption Assembly: Thickened buffer springs and shock pads greatly reduce impact force during lowering, fully protecting threads, snap rings and latch structures of inner tube assemblies and lowering drill tool wear in deep drilling.

1. Wireline fishing without pulling full drill string, greatly improved deep-hole drilling efficiency
Operated by wireline delivery. After coring, there is no need to pull out the whole drill rod string; just lower the overshot to retrieve inner tube and core samples. It drastically cuts the time spent on frequent tripping in deep holes, raises overall drilling efficiency by over 40%, and significantly reduces construction shift cost.
2. Special stable gripping structure for deep-hole heavy load, anti-unhooking and anti-tube dropping
Adopts symmetric widened thickened double lifting dogs, opening flexibly by self-weight with large engagement area. The multi-spring self-locking system keeps dogs fully locked under heavy lifting load to avoid tube dropping. The long-stroke powerful jarring mechanism rapidly loosens common deep-hole problems including tube jamming, core clogging and adsorption locking, greatly cutting down downhole fishing failure rate.
3. Heavy-load wear-resistant alloy material for high-intensity ultra-deep hole operation
The main barrel and lifting dogs are made of premium 30CrMnSiA alloy structural steel with integral medium-frequency quenching and tempering heat treatment, yield strength ≥950MPa. Lifting dogs and friction pairs are reinforced by carbonitriding treatment, with outstanding resistance to high-concentration mud erosion and hard rock collision abrasion, suitable for long-term operation in both clear water and mud drilling media.
4. Compliant with DCDMA international standard, cross-brand universal interchangeability
Fully consistent with global DCDMA wireline coring standards, perfectly matching HQ wireline drill rods, double-tube inner tubes, latch assemblies and joints from all domestic and overseas manufacturers with high accessory interchangeability. Precise fitting tolerances ensure smooth running without jamming and high coaxiality, compatible with all large-torque full-hydraulic deep core drills.
5. Water pressure position warning for safe and controllable deep-hole construction
Standard equipped with ball pressure feedback indicator. Distinct water circuit pressure change will appear after the overshot firmly locks the inner tube, so operators can judge fishing results clearly on rig console, avoiding repeated overshot delivery and reducing invalid operation and downhole risks.
6. Modular standard design for easy disassembly and maintenance in field
All connecting parts adopt standard imperial threads without special locking devices. Wearing parts like springs, lifting dogs and bearings can be disassembled and replaced on site without special tooling. Standardized interchangeable accessories lower inventory cost and support fast maintenance in remote mining areas and wild construction sites.
7. Exclusive advantages of HQ medium-large size, high cost performance for deep exploration
Located between NQ and PQ specifications, HQ overshot features large core diameter, high single-tube core recovery and stable borehole wall, with maximum working depth up to 2800 meters. It is widely used in deep metal & nonmetal mineral exploration, geothermal drilling, large-scale water conservancy, highway & railway survey, deep geotechnical sampling and other ultra-deep coring projects, serving as the preferred mainstream specification for deep drilling works.