Polycrystalline Diamond Cutters Research Articles

Effect of tool wear on machining quality in milling Cf/SiC composites with PCD tool

Carbon fiber reinforced silicon carbide ceramic matrix (Cf/SiC) composites have great application potential in aerospace. But their high hardness and anisotropy cause rapid tool wear during machining, which affects machining quality and efficiency. However, tool wear mechanisms in milling Cf/SiC composites are still unclear. There is a lack of research on the relationship between tool wear and cutting performance. In this paper, milling experiments on 2.5D Cf/SiC composites were conducted using polycrystalline diamond (PCD) cutters. The tool wear mechanisms and effect of tool wear on surface roughness, milling force, burr damage, surface microstructure and chips were explored. The results show that abrasive wear caused by chips continuously scraping tool material and diamond particle fragmentation and falling off caused by sprouting and expansion of cracks inside grain were primary causes of tool failure. The formation mechanism of burr damage was analyzed. It was proved that the peak radius of cutting edge Rpeak and flank wear VB could reflect cutting capabilities. It was found that increasing flank wear had regrinding effects on the cutting edge, which affects the peak radius. The degree of burr damage was related to these two parameters. Tool wear changed the surface formation mechanism. Before tool wear, carbon fibers were primarily removed through the micro-brittle fracture, with low surface roughness. The flank face and chips scratched the workpiece like abrasive grains after tool wear, leaving scratches on the surface and increasing surface roughness from 1.27 μm to 2.25 μm.

Effects of cutting speed and fiber orientation on tool wear and machining quality in milling CFRP with PCD cutter

Milling carbon fiber reinforced polymer (CFRP) composites faces significant challenges, such as rapid tool wear leading to machining damage, even for a polycrystalline diamond (PCD) cutter. However, the effects of the milling conditions on the tool wear of PCD cutters remain unclear. This study investigated the effects of the cutting speed and fiber orientation on the tool wear of a PCD cutter and the corresponding machining quality in milling CFRP. These effects were analyzed by considering fiber and cutter interactions, and milling experiments with a PCD cutter were conducted for validation based on the analyses of cutting-edge profiles, cutting forces, burr area, and machined surface of CFRP. The worn cutting edge profiles were found to be elliptical in shape for cutting CFRP in different fiber orientations owing to the more severe wear on the flank face and cutting edge. Tool wear decreased with increasing cutting speed under a consistent feed per tooth, which further led to a reduction in the cutting force, burr area, and surface roughness. In addition, the maximum and minimum variations of worn cutting edge profiles were found in the cutting of 45° and 135° CFRP, respectively, suggesting that frequently changing the tool working position at 45° could suppress burr damage and increase tool life.

Wear mechanism and quantification of polycrystalline diamond milling cutter in high speed trimming of carbon fiber reinforced epoxy

The use of polycrystalline diamond cutters (PCD) in machining of composite material is increasing. Understanding their wear mechanism and clarity on wear measurement methodology will lead to their productive usage and cost justification. This study focuses on understanding wear in PCD milling cutters at the micro, macro level, and its physical characterization when employed for fibrous composite machining. This leads to the development of a proposal for a clear methodology on consistent wear measurement, which includes a suitable selection of techniques and identification of wear parameters. Continuous diamond skeleton structure made during binder infiltration is captured in worn out PCD edge with the help of scanning electron microscopy. Overall wear process appears to be a complex mixture of losing binder, smaller grains, and pieces of continuous diamond skeleton. This results in cavities of various shapes and forms on the cutting edge making substantial variations in edge recession and edge width. After analyzing, different tool parameters, it was found out that the distance from apex to edge roundness of clearance or rake face is a reliable and repeatable wear parameter. These are shown to be comparable between different wear locations, flutes, and tools suggesting higher wear predictive capabilities. Among different techniques, three-dimensional high-resolution profile scanning of the cutter has been identified as the most efficient tool for tracking wear at regular intervals in tool life prediction studies.

Intense Cooling during Composite Rock Breaking of High-Pressure CO2 Jet-Polycrystalline Diamond Cutter

SummaryIn deep well drilling, rock breaking has some problems, such as low rock breaking efficiency, serious thermal wear of cutters, short service life, and high cost. It is noticed that the application of CO2 drilling fluid in the oil and gas underbalanced drilling is an efficient approach to achieve the reduction of CO2 emissions. Thus, based on the rock-breaking advantages of CO2 jetting, a new rock-breaking method of combing high-pressure CO2 jet and polycrystalline diamond cutter (PDC) is proposed in our study. The cooling mechanism and influencing during rock breaking by using the high-pressure CO2 jet-PDC are conducted. With the test system during composite rock breaking of the high-pressure CO2 jet-PDC, the composite rock-breaking experiment of the high-pressure CO2 jet-PDC was carried out. In the experiment, the comparison of the CO2 jet, N2 jet, water jet, and without a jet was conducted and analyzed. And based on the numerical simulation analysis, the intense cooling mechanism was expounded. In the process during composite rock breaking of the high-pressure CO2 jet-PDC, the intense cooling mechanism was mainly attributed to three main reasons: the thermal effect of the jet flow, the expansion endothermic effect of the jetted flow, and the phase transformation cooling effect of the CO2 jet. The effects of rock samples, jet temperatures, jet flow pressures, and rock temperatures on the cutting temperature were experimentally explored, and finally, the intense cooling rules of composite rock breaking were obtained. The experimental results showed that the CO2 jet had a stronger cooling effect on granite than that of the sandstone. In a certain range, jet pressure was positively correlated with the cutting temperature, whereas jet temperature and heating time were negatively correlated with cutting temperature. The study provides the theoretical support for the CO2 application as a drilling medium in underbalanced drilling.

Experimental Research on Deep-And-Narrow Micromilled Grooves Using a Self-Fabricated PCD Micro-Cutter.

Deep-and-narrow micro-grooves are the common functional structures of miniature parts. The fabrication of the micromilled grooves with high quality and accuracy is the essential guarantee of the causative performance for these miniature parts, and micromilling is the most versatile process to machine such micro-grooves. However, micromilling technology is a highly tool-dependent process, and the commercial carbide micromilling cutter has shown obvious deficiencies in terms of rapid tool wear and inferior machined quality during the machining process. In this paper, a polycrystalline diamond (PCD) micromilling cutter with a large-aspect-ratio (LAR) was designed and prepared by the self-proposed hybrid fabrication method of laser and precision grinding. Micromilling experiments on oxygen-free copper were conducted, and the carbide micromilling cutter was selected in the comparative experiments. The variations of milling forces and specific energy were analyzed through the parameter experiments. Then, the surface quality, machined accuracy and tool wear were further investigated. Results showed that the PCD micromilling cutter with an aspect ratio of 3.25 was successfully manufactured by the proposed hybrid method. The self-fabricated PCD micromilling cutter presented remarkable superiority in terms of the surface quality, machined accuracy, and tool wear when preparing deep-and-narrow micro-grooves. Finally, a satisfactory micromilled groove with an aspect ratio of 2.5 was achieved with the self-fabricated LAR PCD cutter under the optimized conditions.

Impact Failure of Polycrystalline Diamond Cutters

Polycrystalline Diamond (PCD) Cutters are ultra-hard tools used for oil and gas drilling. These tools can fail in the form of spalling due to impact. In this paper, direct impact and quasi-static loading are used to investigate the failure force for leached PCD cutters when loaded at an angle on the edge of their chamfer with a PCD striker or platen. Impact experiments were performed using an impedance match system which ensures the sample is only loaded once; this allows subsequent analysis of the failure surfaces. The failure force at high deformation rate is around 8 kN and at low deformation rate 6.3−+2.3 kN. The failure force required for spalling increases with increasing deformation rate. High speed imaging is also used to explore the failure history of the cutters.

Three-dimensional numerical simulation of the straight shale cutting process of single polycrystalline diamond cutter

The finite element method offers a cost-effective way to test the performance of polycrystalline diamond compact (PDC) cutters, which is much cheaper than lab experiments. However, the finite element simulation often fails to output accurate results, owing to improper model selection and parameter setting. To solve the problem, this paper carries out a three-dimensional (3D) simulation of the straight shale cutting process of a single PDC cutter on finite element software Abaqus. The model size, material model, damage, and failure criterion were determined through triaxial tests on the shale. The adaptive meshing method and mass scaling were adopted to improve the calculation stability and reduce the simulation cost. The simulation reveals the residual stress field in the shale, the reaction force to the PDC cutter, and the relationship between the three components of the reaction force. Based on the simulation results, the authors explored the effects of back rake angle, side rake angle, cutting depth, cutter diameter, and confining pressure on the cutting force and vertical force. Our results were found consistent with those of the previous theoretical analyses and experiments. The numerical simulation of cutter-rock interaction provides an effective way for the design of new PDC cutters.

New features of rock-cutting tools equipped with diamond-carbide cutting elements

The paper describes conducted feasibility study and scientific and technical basis for creation of technology for drilling tools with diamond-carbide cutting elements. The results of technological processes of production of diamond-carbide inserts (DCI) manufactured by Technological Institute for Superhard and Novel Carbon Materials (TISNUM), which are designed for operation and implementation in various drilling conditions were presented. The DCI differentiated physic-chemical and performance characteristics, depending on the physic-mechanical properties of rocks formations, the particular construction of wells and other drilling conditions. A complex of studies of physical and mechanical properties of DCI, their relationship with the structural and technological factors, performance of bits equipped with DCI, the nature of bits wear were conducted, including pilot testing of new polycrystalline diamond compact bits (PDC bits) with polycrystalline diamond cutters produced by TISNUM at the facilities of JSC Gazprom Neft. The possibilities of industrial production of DCI and premium drilling bits on the basis of TISNUM technologies are shown, which will ensure demands of the Russian oil and gas industry, allowing import dependence elimination, and in future start of export. Ultimately, by 2025, with the help of new technologies, it will be possible to occupy up to 25– 30% of the global market for drilling tools and equipment.

Анализ работы алмазных долот при строительстве скважин в сложных условиях

The purpose of the study has been to analyze the operation of diamond drill bits of a PDC type (polycrystalline diamond cutters) in the regions with a complex geological section, and to develop recommendations on optimizing the drill bits. The PDC drill bits are originally designed for soft to medium-hard rocks, thus being ineffective for complex geological sections. As part of the research, the mechanics of the build-up formation on the drill bit cutter and its impact on the rock destruction have been studied. The influence of the pumped drilling mud volume and the pressure differential in the downhole motor on the mechanical drilling speed of the PDC bit has been analyzed. Proposals on improving the geometry and orientation of the tool cutters and optimizing the design of the cutting structure calibratation site and the bit blades have been given; measures on reducing the bottomhole vibrations of the bit during its operation have been suggested. As a result of the study, the mechanism of the build-up formation on the cutter’s working edge and its advance influence on the fracturing in the rock volumetric stratum has been determined. It has been found that the maximum feed of the drilling mud results in the complete absence of the build-up formation and a sharp increase in the mechanical speed of drilling. The study has shown the high performance of high-torque downhole screw motors and defined the optimum range of the pressure differential for the PDC drill bits as a function of the drilling mud flow rate. The authors have suggested the ways to reduce the vibration and stabilize the PDC drill bits by optimizing the structure and geometry of the tool’s cutters and blades, and by using hybrid cutters as auxiliary ones. The conclusion is that the optimization of the PDC drill bits enhances their operation performance under complicated geological-engineering conditions in Eastern Siberia and Yakutia.

ВЛИЯНИЕ КРУТИЛЬНЫХ И ПРОДОЛЬНЫХ КОЛЕБАНИЙ НА СКОРОСТЬ БУРЕНИЯ И ОБРАЗОВАНИЕ ПОЛОМОК РЕЖУЩИХ ЭЛЕМЕНТОВ БУРОВЫХ ДОЛОТ, АРМИРОВАННЫХ PDC

Актуальность. В настоящее время для сооружения скважин на нефть и газ наиболее эффективным инструментом являются долота, армированные пластинами PDC (polycrystalline diamond cutters). Такие долота работают по принципу резания–скалывания, так как из всех механизмов разрушения породы резание является наиболее эффективным по причине того, что прочность породы на растяжение и скол значительно меньше её прочности на сжатие. Анализ состояния отработанных буровых долот, армированных пластинами PDC, показывает, что они отрабатывают свой ресурс не полностью, так как часть режущих PDC элементов выходит из строя по причине скола. Многообразие форм сколов по форме и размерам требует провести классификацию, выявить причину появления и определить нагрузки, приводящие к их возникновению. Кроме того, слом пластин или их потеря в значительной степени сказываются на конечных технико-экономических показателях бурения разведочных и эксплуатационных скважин. Решение вопросов повышения качества долот путем уменьшения числа поломок будет способствовать повышению экономической эффективности работ при добыче и разведке полезных ископаемых. Целью исследования является определение размеров площадок скола пластин PDC для дальнейшей классификации в зависимости от толщины срезаемого слоя породы, причин возникновения крутильных и продольных колебаний в бурильной колонне, вызывающих поломки PDC, а также разработка конструкции бурового долота, армированного пластинами PDC, предупреждающего появление автоколебаний в бурильной колонне. Объекты: режущие элементы буровых долот, армированных пластинами PDC с плоской передней гранью и PDC с выпуклой передней гранью, сколы пластин PDC на буровых долотах, возникающие в процессе бурения скважин. Методы: экспериментально-аналитический метод исследования на лабораторных образцах и на отработанных буровых долотах, армированных пластинами PDC. Результаты. На основании анализа и обобщения результатов выполненных лабораторных исследований причин возникновения поломок пластин PDC и их характера разработан ряд технических и технологических решений, предупреждающих возникновение крутильных и продольных автоколебаний в бурильной колонне и повышающих эффективность породоразрушающего инструмента, армированного пластинами PDC.

Study on characteristics in high-speed milling SiCp/Al composites with small particles and high volume fraction by adopting PCD cutters with different grain sizes

Silicon carbide particle–reinforced aluminum matrix (SiCp/Al) composites were milled at a high speed by adopting polycrystalline diamond (PCD) tools, which the diamond grain sizes were 5, 10, 25, and 32 μm. The machined materials were SiCp/Al composites which the volume fraction was 45% and grain size of SiC particles was 5 μm. The tool wear resistance and wear morphology of polycrystalline diamond cutters were investigated. And it centered on the effects of diamond grain sizes on the cutting forces as well as the machined surface roughness. The obtained results indicated the difference of corresponding tool wear resistance between larger SiC particles and smaller SiC particles during high-speed milling SiCp/Al composites with higher volume fraction. When the grain size and volume fraction of SiC granules are 5 μm and 45%, the tool wear resistances of four diamond grain sizes were all far higher than those of tools in machining composites with higher volume fraction (56%) and larger 60-μm SiC particles. And the PCD tools of larger diamond grain size acted on better wear resistance. Both the corresponding cutting forces and surface roughness were also smaller. As cutting distance increased, the variation law of cutting forces had a good correspondence with the tool wear of PCD cutters of different diamond grain sizes. The machined surface roughness had a decreasing trend in general, but the fluctuation range was tiny. The main wear morphology was flank wear and slight wear groove marks. And there was no chipping of cutting edge and coarse wear groove marks. A large amount of the machined materials was adhered on flake face in the cutting process, but built-up edge was not formed.

What’s Different About These Drill Bits? How a Little Change Can Be Made To Matter

There is not a big difference between those two drill bits. Both have fixed cutters and show some wear. If they look small, that is perceptive. They were used on the automated drilling rigs, which are the scale of machine tools, built by student teams for the Drillbotics competition. The one on the top was designed by the team from the Norwegian University of Science and Technology (NTNU), which was the first to design its own fixed-cutter bit in the competition put on by SPE’s Drilling Systems Automation Technical Section (DSATS). The difference is in the polycrystalline diamond cutters (PDC), and it is not a big one. The ones on the student-designed bit (top) have a lower profile than the one (bottom) provided to all the competitors for free by Baker Hughes, a GE company. Varying the cutter size and angle to change how much rock a bit breaks off per rotation are common design options. When John Macpherson, a senior technical advisor for Baker Hughes and a former DSATS chair, saw it, he said: “It looks like a normal PDC bit.” What made that small difference worth noting are the things the NTNU team did to turn it into a significant advantage. “Even though the designed drilling bit may look like the most important element, it was a combination of a number of factors that allowed them to enlarge the (performance) envelope and drill much faster,” said Alexey Pavlov, a professor of petroleum cybernetics at NTNU who was the faculty advisor on the project. The challenge faced by these teams building something that looks like drilling in miniature is a fundamental one facing engineers building and running drilling machines at a time when the word drilling is married to the word system. Performance will vary based on how well the parts, and people in different disciplines, work together. “Those in drilling need to understand these are systems, not just mechanical devices,” Macpherson said. “We originally started here building mechanical tools with a mechanical engineering group. Then we brought in electronics, software, physics modeling and so on, and now we have a drilling systems engineering group.” That cooperative, multidisciplinary approach required by Drillbotics “very much mirrors (and perhaps leads) real-world approaches,” he said. That complicated stew of the variables attracted Sebastian Knoop, the NTNU student who was the first to volunteer for the university’s Drillbotics team, which was one of their Master’s project options. “Drillbotics was the one I found really interesting. It was a competition. That is the one that lit me up. The mix of drilling, robotics, and automation got me into it,” he said, adding, “I was the first one on the team, then some of my friends got in it as well.” Significantly, they also recruited a “guy not from the same petroleum engineering gang as the rest of us,” he said. That recruit, Mikkel Leite Arnø, majored in industrial cybernetics and provided critical robotics expertise. They were heeding the advice from the Drillbotics judges to the 2017 NTNU team to “try to establish a multidiscipline team next year.”

Effect of rake angle on cutting performance during machining of stone-plastic composite material with polycrystalline diamond cutters

This study investigates the effect of rake angle on cutting performance during machining of stone-plastic composite material with diamond cutters. To that end, an orthogonal cutting experiment was ...

Бурение дополнительных боковых стволов долотами PDC

Бурение дополнительных боковых стволов долотами PDC

Wear resistance of polycrystalline diamond cutters for drill bits

In the present work, the wear resistance of GES 1313 polycrystalline diamond (PCD) cutters (produced by E6), which are cylindrical in form (diameter 13.44 mm, height 13 mm), in turning granite and abrasive wheels at different speeds is investigated. The optimal cutting speed is determined, and comparative data are obtained for the cutting of Mansurovsk granite and 64C (SiC) abrasive wheels, so as to develop recommendations regarding the test conditions for PCD cutters. The wear resistance is characterized in two ways: as the ratio of the loss of volume of the diamond layer to the volume of machined material removed (when it is a dimensionless number); or by the quantity of machined material removed with a fixed degree of cutter wear (when it is expressed in cm3 with respect to 1-mm wear of the rear surface). In cutting granite, the cutting speed varies from 80 to 320 m/min; in cutting abrasive wheels, the cutting speed is 500 m/min. To calculate the volume of the PCD cutters, 3D models of the worn sections are constructed by means of Kompas 3D software, and a calibration curve for determining the volume of material removed by wear at the rear surface of the PCD cutters is plotted. The cutting angle is–22°. The change in volume of the worn section of the PCD cutter with change in the cutting angle from–20 to–25° is less than the measuring precision of the wear area up to 0.8-mm blunting. Increase in speed from 80 to 160 m/min in cutting granite reduces the wear resistance of the PCD cutters by a factor of 12. The relative wear of the PCD cutters in cutting granite is (0.01–0.02) × 10–6, which is 20 times less than in cutting 64C abrasive wheels. The relative wear of the PCD cutters in cutting abrasive wheels does not depend on the blunting of the rear surface up to values of 1.4 mm. This method may be recommended for rapid determination of the wear resistance of PCD. The proposed method of calculating the worn volume of the PCD by means of Kompas 3D or other appropriate software may be used to assess the relative wear resistance of abrasives and cutting materials.

Diamond-CaCO3 and diamond-Li2CO3 materials sintered using the HPHT method

Diamond-CaCO3 and diamond-Li2CO3 materials were sintered at high pressure (8.0GPa) and high temperature (2300°C) for 3min using the infiltration technique. The structure and mechanical properties of the sintered compacts were characterized. It was determined that the melts of carbonates penetrate into the diamond layer to a depth of 4.5mm. The wear resistance of the materials was measured using the free-diamond abrasive-grinding test. The wear resistance of the diamond that was sintered with CaCO3 is 33% better than that of the conventional polycrystalline diamond cutters (PDC). The wear of the diamond that was sintered with Li2CO3 also exceeds conventional PDC by 27%.

Study on rock reaction force depending on PDC cutter placement

ABSTRACTThe article focuses on the problem of polycrystalline diamond cutter (PDC) cutters' overlapping influence on rock reaction force. This study proposed a static force balance model, based on the model of Wojtanowicz and Kuru (1993). The innovation of this model is considering two types of friction forces, acting on the contact frontal surface and the lateral surface of a PDC cutter, respectively. Additionally, the proposed model assumes a rock reaction force direction not orthogonal to the contact surface of a cutter but parallel to the crack propagation direction and similar to the rock heterogeneity direction.Numerical study was provided for a new and a worn PDC cutter to define a rock reaction force depending on options of adjacent cutters' placement (cutters' shape, cutter sizes, bake rake angle, side rake angle, etc.). Two main tendencies were observed: increasing of lateral plot of a cutter decreases rock reaction force, and deviation between directions of cutting force and crack propagation is an extremely significant factor and affects rock reaction force magnitude.

Influence of weave structure on delamination when milling CFRP

The increasing use of carbon-fiber-reinforced plastic (CFRP) is, in addition to weight reduction, driven by decorative elements especially in the automotive industry. Different kinds of woven CFRP laminates are applied for visual effects, which, however, demand a high level of surface quality of the workpiece including the trimmed edges. This study is the first to investigate the correlations between weave induced fiber undulation and delamination when machining CFRP with a woven fabric. In order to analyze the influence of the undulation, several slots were milled into CFRP with a plain weave structure using polycrystalline diamond cutters. The relative position of the trimmed edge to the weave undulation was varied by inclining the milling path slightly relative to the fiber orientation. Surface damage and fiber protrusion from the trimmed edge were determined separately. To identify the fiber undulation angle and thickness of the top matrix layer, tomographic measurements of the laminate were used. Additionally, a theoretical model for maximum fiber protrusion was established. It became apparent that the combination of fiber undulation angle and thickness of the top matrix layer are responsible for different occurrences of delamination. The influence of tool geometry on delamination is less significant.

Study on Brittle Removal Mechanism of Polycrystalline Diamond Based on Surface Micro-morphology

Grinding of polycrystalline diamond(PCD) is an important process in PCD cutter manufacturing. The grinding parameters can strongly influence the removal form of PCD, and determine the performance of the cutting tool. PCD specimens are ground at different grinding conditions and etched using chlorinators acid afterward. Brittle removal mechanism of polycrystalline diamond(PCD), as well as its relation with grinding parameters, is investigated by examining the surface features of pre-etched PCD specimens using scanning electron microscopy. Based on different generation mechanisms, the brittle removal forms of PCD can be classified as micro-cracking, grain-boundary cracking and fatigue-cleavage cracking, and in detail, the micro-cracking form includes cleavage micro-cracking and brittle micro-cracking. Micro-cracking which is the main removal form in the initial stage of wet grinding happens under any grinding condition. Grain-boundary cracking happens when wear particles of diamond wheel are sharp. On the contrary, fatigue-cleavage cracking happens when wear particles of diamond wheel are blunt, especially in the later stages of dry grinding.

Unconventional Polycrystalline-Diamond-Bit Design Allows Significant Performance Gains

This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper SPE 156961, ’Departure From the Norm in Polycrystalline-Diamond-Bit Design Allows Significant Performance Gains in Highly Erosive and Abrasive Formations,’ by Aron Deen, Jason Maw, Craig Knull, and John Clegg, SPE, Ulterra Drilling Technologies, prepared for the 2012 SPE Annual Technical Conference and Exhibition, San Antonio, Texas, USA, 8-10 October. The paper has not been peer reviewed. This paper discusses the design, manufacture, and application of a contiguous blade of polycrystalline diamond (PCD). This bit has full-length, contiguous PCD coverage, without gaps between cutters on each blade, as in a conventional PCD-compact (PDC) bit design. The implementation of this bit represents a step change in bit design. Drill-Bit Damage The traditional view has been that PCD cutters are the most important part of the PDC bit because they are required to engage the formation and maintain their geometrical properties long enough for shear drilling to be economical. The bit body, then, is necessary only in order to hold the cutters in their arranged layout, and to convey mechanical and hydraulic power to remove the rock in their path. PCD cutters are very hard and resistant to abrasion, but are susceptible to damage from their relative lack of toughness. Bit-body materials, whether made of steel or tungsten carbide composite hard facing or infiltrated matrix, are more prone to failure in the drilling environment. One drill-bit design limitation is a requirement for sufficient body material to exist to create a pocket to which the PCD cutter will be brazed. In the case of the webbing be-tween the cutters, depicted in Fig. 1, this puts the body material in a position where it is likely to engage either the formation or high-velocity fluid flow. Invention and Hypothesis The premise that there has to be enough body material to constitute a braze pocket leads to the conclusion that there has to be a webbing between the cutters. The resulting engineering problem was to optimize this webbing, on the basis of the need for cutter exposure and material strength of the body material. But does a braze pocket need to be constructed entirely from body material? Erosion and Abrasion. The first obvious benefit of this new design philosophy should be that, given that there is no weak point of webbing subjected to abrasive or erosive wear, intercutter or cross-blade abrasion and erosion will be mitigated. The webbing between the cutters is the area most susceptible to this mechanism along the fluid path. Abrasion occurs because of the same design weakness—the webbing—but be-cause of a different mechanism. As illustrated in Fig. 2, abrasion is more uniform because of the rotation of the bit. It occurs when the bit body contacts the formation and is worn away. The result, though visibly different from erosion, shares a similarity in terms of location.