Abstract Low-alloy steel drill bits are commonly used in the mining industry for boring holes into rocks. They are characterized by high hardenability and a good combination of mechanical properties, with minimal additions of alloying elements. As product quality improves, the market becomes more competitive. Significant growth in the use of engineering development tools has also occurred, leading to improved performance in rock drilling, oil and mineral exploration, and the search for gemstones. Due to the constant cyclical mechanical stresses applied, the expected life of drill bits is often reduced by fatigue or mechanical wear, indicating that the market consistently requires the availability of new drill bits. This work aimed to demonstrate the suitability of hot forging as a substitute for machining to manufacture the specific profile of the drill bit preform used in rock drilling. A mining-industry partner selected AISI 8640 steel, as it is widely used for drilling applications. Tests were performed with AISI 8640 as a modeling material, and the results from the forging process were used to evaluate the punch movement and consequent metal flow, as well as the filling of the part’s cavity within the forging dies. The results obtained using Elementary Plasticity Theory (EPT) allowed verification of the physical experiment with AISI 8640 steel forged parts. Following this evaluation, numerical modeling was performed and compared with the hot forging process. Formation of the hollow cavity $$\sigma_b$$ within the part and the head of the preform in the same step was assessed. As a result of this optimized process, the reduction in the initial height of the billet and the preform formation were analyzed, with the finishing of the drill bit contingent upon the machining process. This hot forging demonstrated improved material utilization compared to the machining process, highlighting the benefits of deformation through simulations.

PurposeTo investigate the incidence and management of complications associated with all‐inside technique (AIT) anterior cruciate ligament reconstruction (ACLR), and to compare postoperative outcomes between patients with successfully managed complications and complication‐free controls.MethodsA retrospective analysis was conducted on patients undergoing AIT‐ACLR. AIT‐related complications were documented, with a minimum 24‐month follow‐up. Propensity score matching (PSM, 1:2 ratio) was used to compare the complication and non‐complication groups. Knee function was assessed using the Lysholm Knee Score, International Knee Documentation Committee Subjective Score, and Tegner Activity Scale. Stability was measured with the Ligs Digital Arthrometer.ResultsA total of 274 patients were included, with 45 patients (16.4%) experiencing AIT‐related complications. Complications comprised tibial lateral subluxation (21 cases, 7.7%; mean displacement: 2.3 mm, range 2.0–2.5 mm), which resolved spontaneously in 4 patients (19.1%) by 1 month postoperatively and in the remaining cases by 3 months. Femoral suspensory button malposition occurred in 12 patients (4.4%), with only one case (8.3%) requiring immediate revision due to a 7.6 mm displacement. The others (mean displacement: 2.5 mm, range 2.1–3.0 mm) were managed conservatively. Cortical breach at the tibial tunnel exit (7 cases, 2.6%) and flip drill bit breakage (5 cases, 1.8%) were addressed intraoperatively. Following PSM (complication group: n = 45 vs. non‐complication group: n = 87), baseline demographics demonstrated no significant differences except for operative time (p = 0.035). There were no statistically significant differences in knee function and stability between the matched groups at 3, 6, 12, and 24 months postoperatively (p > 0.05 for all).ConclusionPostoperative knee function and stability demonstrated improvement following AIT‐ACLR. Although appropriately managed complications did not substantially compromise clinical outcomes, the findings emphasize the importance of technical vigilance, intraoperative complication management, and preventive strategies to optimize surgical outcomes.Level of EvidenceLevel III, case‐control study.

This work presents a new lubrication strategy for single-stroke drilling of deep holes with a length-to-diameter ratio of eight in austenitic stainless steel SUS 304. The nanofluid used for cooling was prepared in two steps: initially, graphene nanosheets were dispersed into an emulsion, followed by dilution with tap water. All drilling trials were conducted at low pressure and flow rate, using internal lubrication through the drill bit. Compared with conventional emulsions, the nanofluid promoted more effective chip evacuation, lowered thrust force, and consequently prolonged tool life. The results further demonstrated that nanofluid lubrication in deep hole drilling enhanced hole quality, resulting in more uniform diameters and lower burr heights. Using a Taguchi L9 design, the optimal cutting parameters were determined as a spindle speed of 610 rpm and a feed rate of 0.06 mm/rev, which provided the best combination of dimensional accuracy and tool life. This strategy allows continuous deep-hole drilling without pecking, high-pressure coolant, or ultrasonic assistance, while remaining effective for difficult-to-cut materials.

Hardness is a crucial property and indicator of materials, representing their ability to resist the penetration of hard objects into their surface. Particularly in rock mechanics, rock hardness not only serves as a measure of the difficulty in fracturing rocks but is also closely related to rock drillability (i.e., the resistance of rocks to drilling), compressive strength, drill bit selection, drilling efficiency, and rock fragmentation methods. Therefore, in the field of mechanical drilling, the accurate determination of rock hardness becomes critically important. With the advancement of science and technology, humanity has progressively deepened its understanding and research on rock hardness, leading to the invention of various instruments for measuring it. Industrial development has gradually phased out primitive measurement methods such as scratching and scoring, making rock hardness measurements increasingly accurate and steering the process onto a scientific track. This investigation, from the perspective of rock hardness, delves deeply into this significant mechanical property, examines the domestic and international background of rock hardness measurement techniques, summarizes the instruments, tools, methods, principles, and characteristics of rock hardness measurement, and offers insights into the future development prospects of rock hardness measurement.

RELEVANCE. The actual load on the drill bit consists of dynamic and static loads. The high degree of heterogeneity of the rock, as well as the insufficient objectivity in assessing the stress-strain state of the drilling tool, leads to the inability to determine the actual load on the bit and, consequently, to a decrease in the efficiency of well drilling. In practice, a three-axis accelerometer is installed in the telemetry system to measure the frequency of vibrations of the drill bit. However, measuring devices capable of determining the objective impact pulse are currently lacking. THE PURPOSE of this work is to develop a measurement system for determining the pulse of axial vibrations during well drilling based on the dynamics of weakly compressible fluids METHODS. This work analyzes the shortcomings of existing measurement systems used in rotary drilling of wells. A calculation formula has been obtained that correlates the pressure of the fluid in a sealed hydraulic system with the dynamics of external axial forces acting on the system. A prototype of the measurement system has been developed based on theoretically derived mathematical patterns. A program has been created for the measurement system, which implements a low-frequency filter to enhance the quality of output data, as well as a method of mutual correlation to isolate individual impacts. RESULTS. A methodology for measuring the pulse of axial impacts has been proposed based on a hydraulic cylinder installed in close proximity to the bit, along with a set of sensors to measure the state of the fluid inside the cylinder. A model of the measurement system has been developed.

Mud loss is the most common drilling problem and requires substantial time and material expenses to deal with. To prevent lost circulation, inert filler materials are commonly added to drilling mud. These include fine-grade rubber granules and cellophane flakes, corded fiber, granulated rubber, and a mixture thereof; less commonly, nut husk and shell, and other plugging materials that can fill the largest pores and fractures induced while drilling through fractured rock. Typically, particle size and composition of such mixtures are selected considering the size of fractures to be sealed based on geological features of penetrated interval and available experience in drilling of offset wells, while the injected mixture volume is determined beforehand. Therefore, the mixture is distributed across large and small fractures almost completely, so after filler material placement, a «clean» wellbore may be obtained, free of any residue of inert filler material. This is essential because the presence of filler material down hole will cause wear of mud pump (cylinder-piston assembly components) and clogging of bottomhole assembly components. However, sometimes not all filler material is spent on plugging. This leads to filler material plug formation within the target zone, which must be «drilled out» thus requiring additional hole reaming. To improve the efficiency of hole reaming and reduce well construction costs, Tatburneft's emergency response team keeps searching for new solutions. For example, the fourth quarter of 2023 has seen successful pilot implementations of drill bits for hole reaming aimed, among other activities, to improve filler material placement efficiency. The paper presents the design features of the drill bit and outlines its key benefits.

Modelling the effects of drill bit point angle on the temperature and stress distribution on the mandible

The purpose of this study is to identify development directions for drilling tool designs designed for use in frozen rock environments. The primary objective of the study is to analyze existing scientific and industrial experience and examine the mechanism of frozen rock failure during well drilling, thereby identifying the potential advantages of using PDC tools in drilling in frozen rock. This article examines the relevance of developing drilling tool designs designed for penetrating frozen rock. The study is based on an analysis of existing scientific data and production drilling results. An analysis of the failure mechanism and stress-strain state occurring during drilling in frozen rock revealed the key challenges in selecting a tool for well construction in frozen rock intervals. The study's results demonstrated that PDC tools offer the most promising potential for effectively breaking frozen rock, as their working surface allows for responsiveness to changing rock failure conditions. Such rock-breaking tools feature cutters of the required shape, strength, and wear resistance. An analysis of the impact of drilling tool design on the mechanism of permafrost fracture and drilling temperature conditions was conducted. Mathematical transformations were used to derive an expression that clearly demonstrates the dependence of the temperature regime at the borehole bottom on the geometric parameters of the drill bit. It was determined that, all other things being equal, the orientation of PDC cutters can influence the rate of temperature increase at the borehole bottom during drilling. The described approaches to solving these problems point to the possibility of developing a methodology based on a comprehensive analysis of the rock fracture mechanism, enabling the prevention of complications arising during well construction and the regulation of drilling conditions by changing the orientation, shape, size, and arrangement of cutters on the working surface of the tool. The results of this study allow us to identify key areas for the development of drilling tool designs intended for drilling in subzero temperatures.

ABSTRACT This study aims to tackle the dual challenges of efficient production and energy saving in intelligent manufacturing. It explores the potential of Digital Twin (DT) technology in micro-hole drilling production lines for printed circuit boards (PCB), tackling issues of delayed information feedback and low intelligence. The research focuses on three aspects: DT system modelling, data acquisition and transmission, and green dynamic scheduling methods integrated with DT. A visual DT system, comprising physical, twin, and application layers, was developed, enabling mapping, interaction, and visualisation between physical and virtual lines. Considering factors such as operation sequencing, machine selection, adjustable speeds, and energy-saving strategies, a DT-based green dynamic scheduling method for hybrid flow shop production lines was proposed to optimise time and energy. Additionally, a tool life prediction model was incorporated to dynamically reschedule disruptions caused by drill bit breakages. Results show the virtual production line operates smoothly, meeting practical requirements and enhancing management. The DT-based scheduling method improves scheduling efficiency, balancing productivity and energy optimisation. This study provides valuable insights for DT implementation in manufacturing.

Soft coal seams represent a common geological feature in coal and gas outburst mines. They generate a substantial amount of coal debris during gas extraction drilling, which easily causes hole blockage and leads to drilling hazards such as pipe sticking, pipe jamming, and borehole collapse. This study draws inspiration from the burrowing and soil discharge mechanisms of earthworms and proposes a novel composite drilling process that combines “impact vibration + crawling extrusion” for soft coal seams to mitigate these risks and enhance drilling efficiency. Based on discrete element simulation, the effects of drill bit structure, coal seam pressure, and coal seam condition on drilling performance are investigated. The results show that the concave cone bionic bit exhibits the best cutting performance at a buried depth of 400–600 m, with a drilling speed approximately 18% higher than that of other bit structures. The coal seam pressure demonstrates a negative correlation with drilling speed, and the bit displacement at 600 m is 32% lower than that at 400 m. In addition, the drilling efficiency in loose coal seams is considerably higher than in cohesive coal seams, with a displacement difference of 0.025 m/cycle. This study confirms that the proposed high-frequency impact extrusion bionic drilling technology can effectively enhance drilling efficiency and safety in soft coal seams, providing a theoretical basis for the design and optimization of related drilling equipment.

Abstract Epoxy nanocomposites have been globally adopted for various engineering applications owing to their superior thermo-mechanical behavior. A stacked composite was developed using the hand layup method, with five layers of glass fiber between five layers of carbon fiber at the top and bottom. The composite was reinforced with multi-walled carbon nanotubes (MWCNTs) at weight percentages (wt%) of 0.4%, 0.7%, and 1%. One-parameter-at-a-time approach and response surface methodology have been used for the parametric analysis of drilling operation conducted on the fabricated composites at different spindle speeds (800, 1400, and 2000 rpm) and feed rate (80, 140, and 200 mm min −1 ) using HSS drill bit. The effect of input parameters on the thrust and torque force, surface roughness, circularity, and cylindricity has been evaluated. A hybrid approach of Grey Relational Analysis (GRA) and Principal Component Analysis (PCA) has been used to find the optimal input parameters. When MWCNT content increases from 0.4 to 1.0 wt%. at a higher spindle speed of 2000 rpm, the thrust force increases significantly from 24.71 N to 54.59 N (≈120%), whereas the increase of feed rate from 80 mm min −1 to 200 mm min −1 increases torque from 18.96 Nm to 69.53 Nm (approx. 3.7 times). The hole quality at optimal input parameters has been corroborated by morphological analysis using FESEM. Optimization results showed that drilling at 0.4 wt% MWCNT, spindle speed of 2000 rpm, and feed rate of 140 mm min −1 produce holes of optimal quality.

Justification of the drill bit diameter choice based on numerical modeling of fracture of carbonated kerns with healed cracks

Abstract Introduction Penile and scrotal ring entrapment (PSRE) is a rare but potentially serious condition requiring prompt Urologic intervention. It occurs when a constricting object is placed around both the penis and scrotum, leading to impaired circulation, edema, bladder perforation, tissue necrosis, sepsis, and even death. Several techniques have been previously described for the removal of constricting devices both in the setting of the emergency room and the operating room. Due to the variable access to instruments and urologists across care centers, novel approaches to successfully removing constricting devices, especially those made of durable metals, must be made aware to health care personnel. Objective This study aims to review three clinical presentations, management techniques, and outcomes of PSRE in a tertiary care setting with particular emphasis on a novel technique using a Stryker drill commonly utilized by neurosurgeons. Methods Two cases of penoscrotal ring entrapment and one case involving a metal threaded nozzle piece were retrospectively reviewed. The cases were assessed based on duration of entrapment, clinical symptoms, and management techniques utilized. The various removal methods, including manual lubrication, use of ring cutter, bolt cutter, and Stryker neurosurgical drill with a burr drill bit, were evaluated for their efficacy and outcomes. Additionally, existing literature was reviewed to identify highly successful strategies employed by urologists to treat patients with penile, scrotal, and penoscrotal entrapment with rings of various materials. Results All three methods used to alleviate penile or penoscrotal entrapments were safe and effective, including the novel approach using a neurosurgical instrument to remove rings of a tough composition. Poor follow-up was noted for all three cases. Based on literature review a common methodology to treat penoscrotal ring entrapment includes the use of bolt cutters. Additionally, one example of an algorithmic approach to the treatment of penoscrotal entrapment has been proposed. Conclusions Timely diagnosis and appropriate management of PSRE are crucial to prevent complications. The novel use of a neurosurgery drill with burr drill has now been demonstrated as a safe and effective means to remove metal rings around the penoscrotal junction. PSRE should be approached in a fashion that is least invasive to most invasive. Although creativity can be necessary when approaching rare cases, there is a need for a more algorithmic approach. Overall, there is a lack of follow-up in this patient population and educating the patient on common sequelae is paramount. Disclosure Any of the authors act as a consultant, employee or shareholder of an industry for: Coloplast, Medtronic

Abstract To prevent operational breakdowns, it is essential to inspect drill bits for defects following the manufacturing process. Traditional methods to inspect manufacturing defects are not suitable for the drill bits having helical oil holes. These methods are capable to examine surface characteristics but unable to detect internal defects formed during oil hole manufacturing. In this paper, an Operational Modal Analysis (OMA) technique is applied as a Non-Destructive Testing (NDT) to overcome this limitation in detection of manufacturing defects. In this method, the specimen is excited by broadband random vibration and its structural dynamics is analysed by OMA that segregate un-defected and defected drill bits. The proposed algorithm was verified on multiple sets of specimens, and correctly classified all specimens, achieving 100% detection accuracy. The proposed method offers a solution for a more comprehensive inspection by acquiring the dynamic characteristics of the specimen. Nonetheless, its sensitivity in identifying very small defects requires further exploration.

Traditional integral wood joints, despite their strength, durability, and elegance, remain rare in modern workflows due to the cost and difficulty of manual fabrication. CNC milling offers a scalable alternative, but directly milling traditional joints often fails to produce functional results because milling induces geometric deviations—such as rounded inner corners—that alter the target geometries of the parts. Since joints rely on tightly fitting surfaces, such deviations introduce gaps or overlaps that undermine fit or block assembly. We propose to overcome this problem by (1) designing a language that represent millable geometry, and (2) co-optimizing part geometries to restore coupling. We introduce Millable Extrusion Geometry (MXG), a language for representing geometry as the outcome of milling operations performed with flat-end drill bits. MXG represents each operation as a subtractive extrusion volume defined by a tool direction and drill radius. This parameterization enables the modeling of artifact-free geometry under an idealized zero-radius drill bit, matching traditional joint designs. Increasing the radius then reveals milling-induced deviations, which compromise the integrity of the joint. To restore coupling, we formalize tight coupling in terms of both surface proximity and proximity constraints on the mill-bit paths associated with mating surfaces. We then derive two tractable, differentiable losses that enable efficient optimization of joint geometry. We evaluate our method on 30 traditional joint designs, demonstrating that it produces CNC-compatible, tightly fitting joints that approximates the original geometry. By reinterpreting traditional joints for CNC workflows, we continue the evolution of this heritage craft and help ensure its relevance in future making practices.

Airborne acoustic emission-based intelligent wear detection for spatiotemporal data in CNC drill bits using CEEMDAN and ConvLSTM

Summary Accurate formation velocity prediction is essential in drilling engineering, supporting pore pressure estimation and guiding drilling fluid design in strongly heterogeneous strata. Conventional horizon-constrained interpolation, relying on static log velocity, performs poorly with sparse wells or absent real-time logs. To address these limitations, this study proposes a drilling-parameter-driven well-seismic integration method for dynamic velocity updating. A hybrid temporal convolutional network–long short-term memory–feedforward neural network (TCN-LSTM-FNN) model captures nonlinear relationships between drilling parameters and velocity, enabling real-time predictions. By integrating offset well data, real-time drilling parameters, and seismic horizon constraints, a continuously updated low-frequency velocity field is constructed. The interpretability of the model is improved by mapping key drilling parameters to velocity trends. Furthermore, seismic waveform and amplitude details are added to the inversion to enhance resolution and accuracy. The method was validated on the Marmousi2 model, whose strong heterogeneity is ideal for testing velocity prediction. Numerical experiments demonstrate accurate velocity predictions ahead of the drill bit in complex geological settings. Applied to field data from an offshore oil field in eastern China, the method dynamically updated the velocity during drilling, providing reliable predictions around the borehole and ahead of the bit in log-lacking intervals and improving adaptability to complex geological conditions.

Summary In high-temperature, high-pressure (HTHP) wells with a limited safety margin during tripping operations, modifications in the properties of drilling fluid within the well are substantial. Accurate prediction of surge and swab pressures is crucial for secure drilling operations. With this research, we introduce a method for improving surge pressure calculations through a predictive model for drilling fluid rheological parameters. The research investigates the actual condition of the opened-ended pipe (OEP) drillstring configuration beneath a 5-in. drillpipe, considering different yield stress, annular ratios, and tripping velocities. Findings indicate that when the annular ratio is below 0.55 or above 0.65, the drillstring configuration consistently results in either internal pipe blockage or annular blockage, regardless of the yield stress or annular ratio. This method can be extended to various drilling tool combinations through extensive data analysis, facilitating field assessment of drillstring conditions. Additionally, a systematic investigation was simultaneously done on the impact of sensitive parameters, including tripping speed, pump displacement, and annular size, on the surge pressure at the drill bit. The results suggest that accounting for temperature and pressure effects on drilling fluid characteristics may lead to an underestimation of computed surge pressure. In an OEP configuration, higher tripping speeds are feasible; in contrast, in a closed-ended pipe (CEP) configuration, activating the pump during tripping may reduce swab pressure. This study provides both theoretical and operational guidance for managing wellbore surge pressure across different drillstring configurations in HTHP wells, along with a novel approach for accurately predicting wellbore surge pressure.

Integrated failure analysis of tri-cone drill bits using experimental techniques

Natural fiber-reinforced polymer composites are gaining attention due to their low cost, renewable nature, corrosion resistance, and favorable mechanical properties. However, most studies on drilling of natural fiber composites report delamination at only one side of the hole, limiting their applicability in assembly and industrial use. The objective of this study is to fabricate a novel hybrid composite using 30 wt% of sisal fiber, 5 wt% of woven glass fiber, 60 wt% of polyester matrix, and 5 wt% of red mud filler, and to investigate the delamination at both entry and exit sides of drilled holes to optimize machining performance. The composite was fabricated via hand lay-up and compression molding. Drilling experiments were conducted on a numerically controlled vertical drilling machine using HSS drill bits, varying spindle speed (1000, 1250, 1500rpm), feed rate (50, 100, 150mm/min), and drill diameter (6, 9, 12mm) according to an L9 orthogonal array. Delamination was measured using stereo microscopy and ImageJ software, and optimized using Taguchi S/N ratio analysis and ANOVA. Delamination at entry ranged from 1.0403 to 1.1248, and at exit from 1.0400 to 1.1237, showing close agreement. Minimum delamination was achieved at 1250rpm spindle speed, 150mm/min feed rate, and 12mm drill diameter. ANOVA confirmed that drill diameter was the most significant factor, contributing 39.43% at entry and 34.84% at exit, followed by spindle speed and feed rate. Morphological analysis revealed that maximum delamination occurred at 1500rpm of spindle speed, 100mm/min of feed rate, and 6mm of drill diameter, due to fiber pull-out and matrix damage. These results demonstrate that industrial waste-based hybrid sisal/glass fiber composites can achieve good mechanical performance and controlled machinability, providing quantitative guidance for selecting optimal drilling parameters and supporting their use in structural and industrial applications.