Small Diameter Drilling Research Articles

Effect of Different Feed Rates on Chip Evacuation in Drilling of Lead-Free Brass with a Small-Diameter Drill

Effect of Different Feed Rates on Chip Evacuation in Drilling of Lead-Free Brass with a Small-Diameter Drill

Peculiarities of using small-diameter bored piles for effective solving of geotechnical problems

Abstract. The peculiarities of the use of small-diameter drill piles in modern construction considered, with an emphasis on their advantages and areas of application in specific conditions. Two main types of piles distinguished: cast-in-place, which characterized by continuous reinforcement and filling with concrete or cement mortar, and composite, where the load transfers to reinforcing elements. Main advantages of small-diameter bored piles noted, including the possibility of performing work in confined spaces, reducing the level of noise and vibrations, a variety of drilling technologies, the possibility of application in geological conditions of varying complexity, etc. Particular attention paid to the areas of application of small-diameter bored piles, including the installation of new foundations, underpinning of existing structures, soil improvement and land-slide protection. The main groups of factors that can influence the choice of small-diameter bored piles as the main design decision for various fields of application considered, including: - physical factors (restricted access, remoteness of the area, distance of piles to existing structures); - subsoil factors (difficult geological conditions, soil liquefaction tendency); - environmental factors (sensitivity to vibration/noise, hazardous or contaminated soils); - necessity of adaptation to existing structures; - load/settlement requirements; - economic factors. Limitations for the use of small-diameter drill piles from the point of view of their efficiency described. An example of the effective practical use of small-diameter bored piles in the confined conditions of dense urban development in close proximity of metro tunnels with increased requirements regarding the level of vibrations and noise considered. The task of minimizing subsidence of the designed residential and office complex and the impact on surrounding buildings and structures solved. The compliance of the adopted design decisions confirmed by means of field tests, as well as using the results of settlements monitoring. Attention focused on the need for further improvement of design approaches and technological solutions to optimize the efficiency of small-diameter bored piles for solving geotechnical problems.

Laboratory investigation on inhibition of polyvinyl alcohol used for wireline coring drilling

To address the problems of wall collapse, cuttings slurrying, and scaling on the inner wall of the drill pipe, which often occur in small-diameter diamond wireline core drilling, the inhibition properties of polyvinyl alcohol (PVA) was investigated, and the formulation of solids-free drilling fluid with PVA as the inhibitor were completed. PVA has the advantages of fast adsorption and easy regulation of rheological properties Firstly the inhibition effect of PVA was compared with that of common inorganic salts (sodium chloride, NaCl, potassium chloride, KCl) by bentonite dispersion test, linear swelling test, shale rolling recovery test and mud ball immersion test in this study. Then, the inhibition mechanism of PVA was analyzed with potentiometric particle size tests, Fourier transform infrared (FT-IR) and X-ray Diffraction (XRD) measurements. Based on the outstanding inhibition performance of PVA, tackifiers and filtration reducers were preferred through the compatibility test. And finally, the effects of various contaminants on the comprehensive performance of the formulated solids-free drilling fluids were evaluated. The results showed that PVA exhibited better inhibition of clay hydration and dispersion in shale recovery and linear swelling compared to NaCl and KCl, which was particularly evident in the mud ball immersion test. FT-IR and XRD tests revealed that the inorganic salts were used to replace the cations with larger radius and high degree of hydration in the clay layer by ion exchange ti achieve the effect of clay de-watering by reducing the spacing of the clay interlayer and the electrostatic repulsion between the particles. However, PVA is strongly adsorbed on the clay surface in the form of hydrogen bonds due to its unique multi-hydroxyl chain structure, forming a hydrophobic barrier to prevent water molecules from entering the clay layer, thus inhibiting the hydration and swelling of the clay. Using PVA as an inhibitor, compounded with xanthan gum, sulfonated lignite resin and sulfonated gilsonite (FT-1), the solids-free drilling fluid is promising for use in diamond wireline core drilling in complex formations.

Hydrogeological characterization of low permeability medium for conceptualization of a mine site in Eastern Turkey

The mining site in Eastern Anatolia of Turkey were encounter a significant risk of slope instability within the operational area. One of the processes that govern slope stability is the pore water pressure distribution. The conceptualization and characterization of porous media serve as fundamental prerequisites for the implementation of numerical methods aimed at predicting pore water distribution. This study aims to characterize the hydrogeological properties of water bearing rocks in the active mining site in Eastern Anatolia of Turkey. A total of 21 wells and drill holes were drilled in the study area to conduct in-situ tests, monitoring, and sampling. The large diameter wells drilled in surrounding the carbonate rocks were to determine the groundwater flow and boundary conditions and also wells tapped metasediments and diorite unit for hydraulic testing. The lugeon tests and installation of vibrating wire piezometers were carried out at small diameter drill holes to obtain localized hydraulic conductivity of metasediments and diorite at different depths and monitoring pore water pressure distribution along some critical cross-sections. The results obtained from these tests are used for developing hydrogeological conceptual model for groundwater flow. The results of in-situ tests show that the metasediment and diorite units act as a single hydrostratigraphic unit. The metasediments and diorite have high total porosity and low specific yield indicating that the pore water is retained by electrostatic forces in the medium and it resists flow due to low hydraulic conductivity. The vertical variation in hydraulic conductivity values indicates that the medium is highly heterogeneous.

In Situ Measurement of the Machining State in Small-Diameter Drilling by Acoustic Emission Sensing

In drilling small holes with diameters of 1 mm or less, minute clogging and twining of chips or the adhesion of the workpiece material can become factors in causing breakages of the drill bit; moreover, it can be difficult to identify the machining state. Acoustic emission (AE) sensing is a nondestructive inspection technique that measures the elastic-stress waves that are generated when a material is deformed and fractured. AE sensing permits highly sensitive measurements to be made without changing the rigidity of the experimental system, unlike force sensing of cutting resistance, etc. In the present study, attempts were made to identify the machining state and tool wear, and to predict abnormalities in small-diameter drilling by using the change in the frequency of AE signal waveforms arising from deformation and fracture. It was shown that it is possible to predict the breakage of the drill bit by detecting high-frequency AE signals at about 1 MHz, caused by the adhesion of the workpiece material. In addition, a correlation map of the AE frequency spectrum for identifying the machining state in a drilling operation is suggested.

Comparison of the bearing capacities of a small-diameter bored pile obtained from the results of field tests and numerical modeling

Abstract. The paper compares the results of modeling static soil tests with a small-diameter drill pile with the data obtained from field tests. The calculations were performed by numerical modeling using the PC software "Plaxis", which is based on the finite element method. This problem was solved in a flat (2D) formulation for an axisymmetric model, which makes it possible to analyze the stress-strain state (SSS) and the interaction of elements of the pile-soil environment system.
 Separate computational models were created for two types of piles made using different technologies: a bored- CFA pile and a drilled pile with partial soil displacement. In order to take into account the preload history in order to maximize the models' approximation to real conditions, the calculations were performed in 4 stages in accordance with the construction sequence: Stage 1 - initial stage (determination of the initial stresses in the soil massif in the natural state), Stage 2 - excavation to the design mark of the pit bottom, Stage 3 - testing of the soils with a pile by static load. Stage 4 - pile unloading. Based on the results of the calculations, the SSS and the interaction of the elements of the "pile-soil environment" system have been analyzed and compared the settlement graphs obtained from the results of the calculations with the data of field tests.
 It is shown that the use of a plane axisymmetric FEM is a sufficiently effective approach for assessing the stress-strain state and understanding the interaction of elements of the pile-soil system, as well as predicting the bearing capacity of piles for further design of the pile foundation before obtaining the results of field tests. In addition, the labor intensity and time consumption of this approach are relatively low compared to other alternative methods.
 With appropriate experience in using this approach in different soil conditions with appropriate comparison with field test data, it can be applied in the feasibility study and final decisions on the choice of a particular type of foundation.

Clinical application study of multiple small-diameter drilling combined with extracorporeal shock wave therapy (ESWT) under C-arm positioning in the treatment of early femoral head necrosis

To explore the therapeutic effect of multiple small diameter drilling combined with extracorporeal shock wave therapy (ESWT) under C-arm X-raylocalization in patients with early osteonecrosis of the femoral head (ONFH). A total of 106 cases of early ONFH patients admitted from May 2015 to May 2017 were retrospectively selected as the study subjects. According to different treatment methods, the patients were divided into observation group and control group, 53 cases in each group. The observation group was treated with multiple small-diameter drilling combined with ESWT under C-arm positioning in the observation group, including 41 males and 12 females with an age of (45.85±6.01) years old (22 to 70 years old);and the control group was treated with ESWT, including 34 males and 19 females with an age of (45.12±5.83) years old(20 to 68 years old) in the control group. The modified Harris hip scores(mHHS), visual analog scale(VAS), hip flexion range, hip abduction and adduction range, ONFH area ratio and clinical efficacy were compared between twe groups before and after treatment. Kaplan-Meier method was used to draw a survival curve to compare the femoral head survival rate between two groups during the 3-year follow-up period after treatment. There were no complications such as poor wound healing and infection. All of 106 patients were followed up for 28 to 36 months with an average of (31.06±4.28) months. MHHS score, hip flexion range and hip abduction and adduction range in the observation group were increased from (63.85±5.42) scores, (23.79±2.21) °, (32.40±4.19) ° before treatment to (85.51±5.69) scores, (34.65±2.73)°, (43.32±5.71)° at 2 years after treatment, respectively(P<0.05). The above indicators in the control group increased from (64.73±5.64)°, (23.82±2.18)°, (32.45±4.13)° before treatment to (81.65±5.48) scores, (32.79±2.87)°, (39.75±5.68)°at two years after treatment, respectively(P<0.05). VAS score and ONFH area ratio in the observation group decreased from (5.76±1.41) scores and (35.07±4.96)% before treatment to (3.39±1.02) scores and (22.04±3.23)% at 2 years after treatment, respectively(P<0.05). The above indicatiors in control group decreased from (5.73±1.45) scores and (35.24±5.18)% before treatment to (4.43±1.21) scores and (28.32±3.76)% at 2 years after treatment, respectively(P<0.05), and the improvement in the observation group was significantly higher than that in the control group(P<0.05). At 3 years after treatment, the femoral head survival rate in the observation group was higher than that in the control group (P<0.05). Multiple small diameter drilling combined with ESWT under C-arm positioning can significantly improve the clinical symptoms of patients with early ONFH, relieve pain and improve clinical efficacy.

Surgical Technique: Core Decompression of Femoral Head Osteonecrosis with Bone Marrow Aspirate Concentrate.

Osteonecrosis of the femoral head is a progressive and potentially debilitating disorder that is responsive to core decompression, especially in early-stage disease. This is typically accomplished through use of an 8 to 10mm trephine or multiple, small-diameter percutaneous drilling. Use of the large diameter trephine is associated with risk of fracture and may not allow healing across large gaps. Here, we present a technique for core decompression using percutaneous drilling that allows bone marrow aspiration concentrate to be introduced. We used the aspirate needle to decompress the femoral head osteonecrotic lesion, followed by the administration of bone marrow aspirate concentrate. This is a straightforward procedure that can be used with low risk for patient morbidity.

Модифицирование поверхности быстрорежущего инструмента совместным насыщением вольфрамом и азотом

Research significance is contingent on the requirement strengthening for high-speed cutting tools performance and wide-spread introduction of automatic lines and NC-machines. An increase of the tool service life is also necessary for the reduc-tion of putting expensive alloying elements to use, primarily, tungsten. The solution of these problems requires the use of technologies for hardening cutting surfaces. Combined processes of thermochemical treatment processes, uniting diffusive surface alloying with nitrogen saturation have shown their effectiveness in the surface hardening of various steels. Now the aim is to study the process of combined surface tungsten and nitrogen saturation of high-speed steel for increasing small-sized tool durability. Experimental studies were carried out on samples and small-diameter drills made of P6M5 steel. For laboratory experiments connected with combined process of thermochemical treatment an installation for nitriding in multi-component media was used. Metallization with tungsten was carried out by the slip method with parallel nitriding of the tool in a glow discharge. To determine the regime that provides the necessary temperatures for oxygen and nitrogen saturation, the temperatures of the control steel samples were measured on the surface and in the core at different durations of the cur-rent pulse in the heating phase. Metallographic analysis proved that thermochemical treatment resulted in a modified sur-face layer with a thickness of 10…15 microns, formed in P6M5 steel. The structure of the layer is an internal nitriding zone, which consists of a solid tungsten and nitrogen solution in iron and dispersed inclusions of tungsten nitrides. Dispersion and solid solution hardening provide a two-fold increase in the microhardness of the modified W-N layer compared to the alloy base. A transitional diffusion zone of nitrogenous martensite has been revealed under the hardened layer, creating a smooth microhardness gradient from the layer to the core, protecting it from embrittlement, peeling and staining. Using a metallophysical simulated test in predeveloped methodology, the calculation of the hardening index of the modified layer (yield point increase) was made. It showed that with increase in the concentration of tungsten in the layer, the proportion of the component of the dispersion hardening by W2N particles also increases. Full-scale tests in production conditions showed that the tool with a hardened layer had increased resistance. The durability of drills, determined by the number of drilled holes made before its dropping-out, increases by 2,2 times when drilling on 30XGSA steel and by more than 7,0 times when drilling a titanium alloy VT-23.

Effect of Drilling Parameters and Tool Geometry on the Thrust Force and Surface Roughness of Aerospace Grade Laminate Composites.

Carbon fiber-reinforced plastics (CFRPs) have been specially developed to enhance the performance of commercial and military aircraft because of their strength, high stiffness-to-density ratios, and superior physical properties. On the other hand, fasteners and joints of CFRP materials may be weak due to occurring surface roughness and delamination problems during drilling operations. This study's aim is to investigate the drilling characterization of CFRPs with different drilling parameters and cutting tools. Drilling tests were performed with the Taguchi orthogonal array design (L18: 2^1 3^3). Tests were conducted with three levels of cutting speed (15, 30, 45 m/min), three levels of feed rate (0.05, 0.1, 0.2 mm/rev), two levels of drill diameter (3 and 5 mm), and three different types of drills (two twist drills with a point angle of 138° and 120° and one brad drill). Thrust forces were recorded during drilling tests, and afterwards surface roughness and hole delamination were measured. Obtained results were analyzed with Taguchi and two-way ANOVA. The general tendency was that low cutting speed, high feed rate, and small diameter drill caused an increase in thrust force. Surface roughness decreases with increasing tool diameter, decreasing feed, and cutting speed. Delamination factors of the samples dropped depending on decreasing thrust force levels. Remarkably, it is possible to control the delamination factor values via better surface quality. The brad drill and larger point angle have a negative effect on the drilling quality of CFRPs. According to all results, the cutting speed of 45 m/min and feed rate of 0.05 mm/rev using a type II drill having a 120° point angle and 5 mm diameter (12th trial) and the cutting speed of 30 m/min and feed rate of 0.05 mm/rev using a type II drill having a 120° point angle and 3 mm diameter (2nd trial) were determined as optimum drilling conditions.

Machine Tool Equipped with a Counter Balance Feed Drive in the Z Direction with Right and Left Ball Screws and the Influence of Anisotropic Mechanical Behavior on Small-Diameter Drilling Processes

In recent years, electronic devices have become lighter, thinner, shorter, smaller, and more multifunctional, motivating micro drilling technology to become more sophisticated. To meet the demands of electronic applications, this paper proposes a drilling machine tool with a counterbalance vibration control mechanism. In this report, focusing on the timing of table feed rate changes during drilling, drilling experiments were conducted using four drilling paths while changing the table movement direction and feed rate along the machining path. The accuracy of the positions of the drilled holes and condition of the drill edge after drilling were then evaluated.

Mining-Induced Seismicity during Development Works in Coalbeds in the Context of Forecasts of Geomechanical Conditions

Mining-induced seismicity in the area of development works and proper mining operations is one of the major determinants of the rockburst hazard level in underground mines. Rockburst hazard assessment in Polish collieries is performed by a variety of mining and geophysical methods, including seismic and seismoacoustic techniques, borehole surveys, small diameter drilling, rock strata profiling and analyses of geomechanical properties of rocks, geological structure and geological mining conditions. In the case of zones particularly exposed to potential hazards, it is recommended that analytical or numerical forecasts of the state of stress in the vicinity of workings should be used already at the stage of planning of mining operations. This study summarises the comparative analysis of seismic test data and analytical forecasts of the state of stress in five selected headings in one of the burst-prone collieries within the Upper Silesia Coal Basin in Poland (USCB). As regards the seismic data, duly defined quantitative indicators and energy criteria of the registered seismic activity are recalled in the assessment of rockburst hazard level during the roadheading operations. Analytical simulations utilise a developed geomechanical model and stress–strain relationships stemming from the principles of elastic media mechanics. From the standpoint of mining engineering practice, interpretation of results obtained by the two methods reveals how effective analytical models will be in prognosticating or verification of rockburst hazard conditions.

Influence of a Novel Drill Design on Heat Generation During Conventional and Guided Implant Osteotomy.

The aim of this in vitro study was to evaluate the temperature development of a novel, electropolished drill design during conventional and guided implant osteotomy in comparison to conventional drills under standardized conditions. Single and sequential 12-mm-deep drilling protocols (guided and unguided) with a conventional (control groups) and novel drill (test groups) were performed in artificial bone blocks under external irrigation. Each drilling protocol was repeated 30 times with drill diameters of 2.2, 2.8, 3.5, and 4.2 mm. Temperature changes were recorded by an infrared camera, and the accumulated thermal energy was calculated. For group comparison, a one-way analysis of variance (ANOVA) and Tukey post hoc test were used with a level of significance set to = .05. The highest temperatures were measured up to 77.9°C for small-diameter drills in the control and test groups. The 3.5-mm and 4.2-mm novel drills showed significantly lower heat generation during guided and unguided osteotomy preparation for single and sequential drilling. The accumulated thermal energy during guided osteotomy preparation was significantly lower with the electropolished drills. The drill design has an important impact on heat development during osteotomy, which was most pronounced for guided osteotomy with conventional drills and for small-diameter osteotomies.

Drill holes deflection determination for small diameter bits in wood-based materials

The growing interest in wood accessories has focused scientific research attention on wood cutting with small diameter tools. A problem that may arise when drilling wood is the phenomenon of wandering – when the hole is not made in the designed place. The difficulty in studying small diameter drill holes (0.5 mm to 0.9 mm) is due to the difficulty of automatic measurement. The development of an appropriate methodology may allow for the observation of this phenomenon without the need for high-class hardware and expensive software. This article presents the results of tests carried out on nearly 500 samples made of various wood-based materials (high-density fiberboard (HDF), medium-density fiberboard (MDF), chipboard, and plywood) in terms of the usefulness of the OpenCV computer vision library for the determination of wandering.

Small-diameter drilling by ultrasonic vibration workpiece

Small-diameter drilling by ultrasonic vibration workpiece

Influence of concrete bleeding due to mix proportion on the drilling speed of hardened surface layer

<abstract> The significance of micro-destructive testing, which can estimate the durability of reinforced concrete structures with minimal damage and high accuracy, in the investigation and diagnosis of reinforced concrete structures has been increasing. This study aims to evaluate the quality of the surface layer of concrete structures via a small-diameter drilling test, which is one of the micro-destructive tests developed to estimate the strength of concrete. Hence, it would be possible to evaluate the quality and strength of concrete simultaneously, which is very important. In this study, the influence of the bleeding amount which affects the surface quality of concrete on the drilling speed, was experimentally studied, considering the water-cement ratio and unit water content as experimental factors. The influence of bleeding on the drilling speed of the specimen surface was also investigated through measurements at the top and bottom surfaces. The following points were clarified from the experimental results and their analysis. (1) The drilling speed changes depending on the water-cement ratio and the unit water content. (2) The amount of bleeding affects the drilling speed; however the drilling speed is affected by the volume of the fine aggregate in the specimen. Therefore, (3) there is a possibility that it can be used for surface quality evaluation of concrete by examining in detail the method for calculating and correcting the drilling speed. </abstract>

The method of calculation of the deviation of the tool axis when machining small diameter holes

The article is devoted to an important parameter that characterizes the accuracy of the shape and location of the hole after machining — the displacement of the hole axis. When designing operations for drilling small-diameter holes with a large depth (the ratio of the hole depth to its diameter is more than 10), a method for predicting this parameter is necessary to improve the accuracy of work. The article considers the causes and methods of eliminating this negative impact on hole machining using the example of a small-diameter drill axis runout. Recommendations are given for reducing drill runout: to reduce cutting modes; to perform the drilling operation while rotating the workpiece, which can stabilize the drill position during machining; to use drills made of hard alloy or obtained by powder metallurgy methods, which increases their rigidity; before drilling the workpiece, to center the hole with a more rigid drill.

In-vitro assessment of bone viability with different implant drill speeds.

The success of implant osseointegration is clearly impacted by the heat produced throughout the implant osteotomy site preparation. Bone necrosis of the implant bed should be prevented to maintain a stable osseointegration process. The objective of this experiment was to validate the impact of implant drill speed on the bone from the point of view of heat generation; a second objective was to evaluate viability of the osteotomised implant sites in rabbits histologically. Twenty healthy adult rabbits, were randomly categorised into 4 groups; 3 bony osteotomies in the 3 mm, 3.5 mm and 4 mm diameters of the femur were made in each rabbit. Variable speeds were used for the 3 diameters as follow: Group I: speed 1000 rpm, Group II: speed 1500 rpm, Group III: speed 2000 rpm. A combination of speed 2000 rpm for the small diameter drills and the last large diameter with speed 1000 rpm was used in Group IV. The temperature changes were recorded. After the operation, the rabbits were euthanised and the bony samples were taken for histological evaluation. In group III and Group IV, histological analysis demonstrated more bone viability compared to other groups. Furthermore, heat analysis revealed significant differences between group III, Group IV and the other groups with less heat produced with greater speeds compared with lower speeds. Drilling with higher speed in dense bone with irrigation produces less heat and maintains more bone viability compared with lower speed. In addition, increased drill diameter with the same speed or with increased speed generates less heat compared with smaller diameters.

Study on the outcome of patients with aseptic femoral head necrosis treated with percutaneous multiple small-diameter drilling core decompression: a retrospective cohort study based on magnetic resonance imaging and equivalent sphere model analysis

BackgroundAseptic necrosis of the femoral head (ANFH) has a high incidence in the community and causes substantial problems with health as well as economic and social stress. Core decompression is the most commonly used treatment for early ANFH. Although many studies have reported on the efficacy of femoral head core decompression surgery for ANFH, there are still some shortcomings in assessing the severity of femoral head necrosis, the location distribution, and changes in necrotic lesions before and after surgery. Magnetic resonance imaging (MRI) and equivalent sphere model analysis were used to further clarify the clinical efficacy of percutaneous multiple small-diameter drilling core decompression in patients with ANFH.MethodsFrom July 2013 to November 2016, 24 patients (32 cases of the hip joint) with ANFH who underwent percutaneous multiple small-diameter drilling core decompression were selected, and a retrospective analysis was conducted. MRI as well as VAS, OHS-C, and HHS scores were used to evaluate joint function in all patients before and 6, 12, and 24 months after the operation.ResultsTwenty-four months after the operation, 10 hips were amputated. The survival rates of alcoholic femoral head necrosis (AFNH), idiopathic femoral head necrosis (IFHN), and steroid-induced femoral head necrosis (SIFHN) patients at 24 months were 100%, 85.7% (− 2 hips), and 0.0% (− 8 hips), respectively. The MRI and equivalent sphere analysis results revealed that the anterior superior medial quadrant was the area most prone to osteonecrosis, and the posterior superior medial quadrant was the area second most prone to necrosis. After the operation, the average percentage of the AFHN necrosis area in the total volume of the femoral head decreased from 14.5 to 10.3%, and the average percentage of the IFHN necrosis area decreased from 16.3 to 9.2%; however, the average percentage of the necrosis area for SIFHN increased from 30.4 to 33.1%.ConclusionPercutaneous multiple small-diameter drilling core decompression significantly reduced the lesion volume for AFHN and IFHN, but the effect on SIFHN was not good.

Small-Diameter Subchondral Drilling Improves DNA and Proteoglycan Content of the Cartilaginous Repair Tissue in a Large Animal Model of a Full-Thickness Chondral Defect.

This study quantified changes in the DNA content and extracellular matrix composition of both the cartilaginous repair tissue and the adjacent cartilage in a large animal model of a chondral defect treated by subchondral drilling. Content of DNA, proteoglycans, and Type II and Type I collagen, as well as their different ratios were assessed at 6 months in vivo after treatment of full-thickness cartilage defects in the femoral trochlea of adult sheep with six subchondral drill holes, each of either 1.0 mm or 1.8 mm in diameter by biochemical analyses of the repair tissue and the adjacent cartilage and compared with the original cartilage. Only subchondral drilling which were 1.0 mm in diameter significantly increased both DNA and proteoglycan content of the repair tissue compared to the original cartilage. DNA content correlated with the proteoglycan and Type II collagen content within the repair tissue. Significantly higher amounts of Type I collagen within the repair tissue and significantly increased DNA, proteoglycan, and Type I collagen content in the adjacent cartilage were identified. These translational data support the use of small-diameter bone-cutting devices for marrow stimulation. Signs of early degeneration were present within the cartilaginous repair tissue and the adjacent cartilage.