Twist Drill Bit Research Articles

Investigation of tool wear behavior in CFRP drilling by using different tool materials

Abstract The industrial usage of Carbon fiber reinforced polymers (CFRP) has increased significantly over the past few years due to its distinguished characteristics like great strength-to-weight ratio, fatigue resistance, superior damage tolerance, excellent corrosion resistance, etc. Machining of CFRP differs from traditional machining due to its structure. This experimental study aims to investigate the effect of drill bit material on tool wear and to optimize the material selection process of twist drill bits during CNC drilling of CFRP regarding the output of tool wear, thrust forces, and torque generated during the drilling process. Four twist drill bits with dissimilar materials (i.e., HSS-4341, HSS-M2, HSS-Co, and Tungsten Carbide) having the same size and diameter (3mm) were selected and used for CNC drilling on CFRP plates. During the drilling process, thrust forces and torque were calculated with the help of a dynamometer for each drilled hole. Moreover, the tool wear was seen and compared after the 1st hole and 20th hole for each drill bit to analyze the behavior of different tool materials toward CFRP machining. The results showed that Tungsten Carbide is the most suitable tool material for CFRP drilling as it yielded the lowest thrust forces and lowest torque for all 20 holes. Moreover, the Tungsten Carbide had the lowest tool wear among all the drill bits. These results imply that tool life can be significantly elevated if Tungsten Carbide is to be used for machining of CFRP.

Gray relational analysis for parametric optimization of micro-EDM of thermo-mechanically processed AA7075 and AA7075/SiC/Gr composite

The AA7075 alloy and AA7075/SiC/Gr hybrid composite prepared by the stir-casting method have been further thermo-mechanically processed through unidirectional hot rolling and hot cross-rolling routes to eliminate casting defects like voids, blow holes etc. Three initial sample temperatures, that is, 350℃, 400℃, and 450℃, have been considered for the hot cross-rolling. The Al alloy and its hybrid composite prepared at different rolling temperatures are studied to investigate their micro-machining behavior through micro-electric discharge machining (µ-EDM). The micro-holes are made on the rolled samples along the rolling direction of the final rolling pass using a tool with twist drill bit geometry. Further, multi-objective optimization of the µ-EDM process parameters considering the response parameters viz. material removal rate (MRR) and tool wear rate (TWR) has been carried out using the gray relational analysis (GRA) technique. The µ-EDM parameters chosen to optimize in this study are voltage, pulse on time, and tool rotation. The obtained GRA results are further analyzed through normality and equal variance tests. The R-squared values of 95.02% and 95.53% for AA7075 alloy and hybrid composite, respectively, indicate that the data fit well with the statistical model. In material removal, the different electrical and thermal characteristics of the Al matrix and the reinforcements possibly generate sparks with a different characteristic that ultimately affects the MRR of the composite. Through scanning electron microscopy (SEM), the morphological study confirmed the presence of globules and voids on the machined surface. The formation of globules and voids is more significant in the AA7075 alloy than in the composite.

Soft material drilling: A thermo-mechanical analysis of polyurethane foam for biomimetic bone scaffolds and optimization of process parameters using Taguchi method

Drilling is a widely employed technique in machining processes, crucial for efficient material removal. However, when applied to living tissues, its invasiveness must be carefully considered. This study investigates drilling processes on polyurethane foam blocks mimicking human bone mechanical properties. Various drill bit types (118° twist, 135° twist, spherical, and conical), drilling speeds (1000–1600 rpm), and feed rates (20–80 mm/min) were examined to assess temperature elevation during drilling. The Taguchi method facilitated systematic experiment design and optimization. Signal-to-noise (S/N) ratio and analysis of variance (ANOVA) identified significant drilling parameters affecting temperature rise. Validation was conducted through confirmation testing. Results indicate that standard twist drill bits with smaller point angles, lower drilling speeds, and higher feed rates effectively minimize temperature elevation during drilling.

Standardized Testing for Thermal Evaluation of Bone Drilling: Towards Predictive Assessment of Thermal Trauma.

To ensure the prevention of thermal trauma and tissue necrosis during bone drilling in surgical procedures, it is crucial to maintain temperatures below the time- and temperature-dependent threshold of 50 °C for 30 s. However, the absence of a current standard for assessing temperatures attained during bone drilling poses a challenge when comparing findings across different studies. This article aims to address this issue by introducing a standardized testing method for acquiring thermal data during experimental bone drilling. The method requires the use of three controlled variables: infrared thermography, standard bone blocks, and a regulated drilling procedure involving a drill press with irrigation that simulates a surgeon. By utilizing this setup, we can obtain temperature data that can be effectively applied in the evaluation of other variables, such as surgical techniques or drill bit design, and translate the data into bone damage/clinical outcomes. Two surgical drill bits (2.0 mm-diameter twist drill bit and 3.3 mm-diameter multi-step drill bit) are compared using this experimental protocol. The results show the 2.0 mm bit reached significantly higher temperatures compared to the 3.3 mm bit when preparing an osteotomy (p < 0.05). The 2.0 mm drill bit reached temperatures over 100 °C while the 3.3 mm drill bit did not exceed 50 °C.

Drilling performance of micro-textured twist drill bit for TI-6AL-4V alloy: Validated FEM and statistical approaches

The titanium alloy, particularly Ti-6Al-4V, is an extensively demanded material in diverse sectors because of its superior physical and chemical properties. Nevertheless, the inherent hardness of the material causes challenges during machining operations. The alloy's heat-resistance characteristic induces increased friction and heat generation on cutting tools, ultimately causing a decrease in the tool life. In an attempt to overcome this issue, numerous forms of surface texturing have been investigated with the aim of improving the tribological characteristics of the material. The aim of the present investigation was to enhance the cutting performance of drill bits by implementing micro-textured patterns, hence minimizing thrust force, torque, and tool temperature. The combined effect of three distinct micro-textured geometries on a drill bit's flank, flute, and margin surfaces, with the influence of coating conditions, on the performance of drilling operations was investigated. The Finite Element Method (FEM) was used to perform a range of varied drilling operations. The Grey Relation Analysis (GRA) and General Linear Model (GLM) were employed to assess and compare the drilling performances with respect to thrust force, torque, and drill bit temperature. It was found that the square-sectioned textures on the side face exhibited the most obvious influence on the drilling performance. In the meantime, the textures found on the flute face were identified as having a comparatively smaller influence. The ideal configuration for the drill bit entailed a flank face with a square sectioned texture, a flute face without any texture, a margin face with a square sectioned texture, and a hard coating. As a result, the current situation substantially reduced cutting forces, tool wear, and tool temperature by 51 %, 20.5 %, and 23.4 % compared to the drilling condition without textured drill bits.

Thermal-mechanical coupling in drilling high-performance CFRP: Scale-span modeling and experimental validation

The focus of this study is to explore a scale-span thermal–mechanical coupling method for predicting the dynamic mechanical progressive failure behaviors and predicting thermal damage during the drilling process of Carbon Fiber Reinforced Plastic (CFRP). Initially, a thermal conduction constitutive model of drilling CFRP was developed based on the proposed thermal distribution ratio calculation method. Meanwhile, a dynamic span-scale progressive damage constitutive model for CFRP, incorporating modified micromechanics failure criterion with bilinear damage evolution laws, was proposed, and a bilinear cohesive model, including three damage modes, is employed to simulate interlaminar delamination. Subsequently, a user-defined material subroutine VUMAT was implemented on the ABAQUS/Explicit platform to simulate the thermal–mechanical coupling behaviors of drilling T700S-12K/YPH-23 CFRP using a twist drill bit. Finally, a comprehensive information monitoring platform for CFRP drilling experiments was established to validate the accuracy of the simulation results by considering drilling temperature, thrust force, and hole-wall morphology. The results demonstrate excellent agreement between the established thermal–mechanical coupling span-scale model and the experimental data. Furthermore, the simulation effectively captures the various damage behaviors and thermal conduction phenomenon, that occur during the intact drilling process.

A study on the ultrasonic vibration on the cutting performance during ultrasonic-assisted drilling of CFRP with twist and dagger drill bits

During the drilling process of carbon fiber reinforced polymer (CFRP), defects such as exit delamination, tearing, and burrs are prone to occur, among which excessive axial force during drilling is the main reason for the generation of exit delamination defects. In this study, ultrasonic-assisted and conventional drilling with twist and dagger drills were investigated on 5 mm-thick multi-directional laminated fiber sheets made of T300-12k/AG80 carbon fiber composite with different orientations. The axial force evolutions in each case were monitored when drilling holes in CFRP plates, and the axial force of drilling and the appearance characteristics of hole outlet were compared. The experimental results showed that the ultrasonic assisted drilling reduced the axial drilling forces of twist and dagger drill by up to 20.6% and 30.7%, respectively, compared to conventional drills. In addition, as the feed rate increases, the axial force of drilling gradually increases, and the exit delamination factor shows an overall increasing trend. The ultrasonic vibrations reduced the exit delamination damage of both drills. A special structure of the dagger drill effectively avoided exit delamination during ultrasonic-assisted drilling, which makes the incision more neat to improve the processing quality.

Drill Bit Design and Its Effect on Temperature Distribution and Osteonecrosis During Implant Site Preparation: An Experimental Approach

In this study, the drilling parameters will be evaluated to obtain optimal parameters in minimizing the impact of drilling damage on synthetic bone blocks. The effect of damage observed in the study is osteonecrosis that occurs in the drill hole for implant site preparation, where a smaller value is desired. The drilling parameters are optimized using the Taguchi method with two control factors: the feed rate and spindle speed; each parameter is designed in five levels. This experiment was then carried out on four different designs of drill bits, i.e., Twist (118°and 135°), spherical, and conical drill bits. While experimental planning uses L25 orthogonal arrays, the “smaller is better” approach is used as a standard analysis. The main findings of this research are 118° point angle twist drill bit is the ideal type of drill bit for bone drilling, as it produces less heat than other types of drill bits. The optimal range of feed rate and drilling speed for bone drilling is 40-60 mm/rev and 1000-1400 RPM, respectively. Combining these parameters helps to minimize heat generation during implant site preparation drilling.

Conical drill bit for optimized external ventricular drain placement: a proof-of-concept study.

Despite external ventricular drain (EVD) procedures being commonplace in neurosurgical practice, suboptimal placement rates remain high, and complications are not uncommon. The angle of the EVD catheter insertion and the accuracy of the drill hole placement are major factors determining successful EVD placement that are dependent on the drill bit morphology. The standard cylindrical 2-fluted twist drill bit creates a relatively deep and narrow drill hole that requires precise positioning, has limited visibility of the drill hole bottom and restricted catheter angular adjustment range, and poses the risk of inadvertent dural puncture. To overcome the standard problems associated with EVD drill bit morphology, the authors propose novel cone-shaped drill bits for EVD placement. Conical drill bits of 30° and 45° were designed, manufactured, and tested in a simulated laboratory setting as well as in three human cadavers with intact skull, dura mater, and brain. Drill bit performance was rated by neurosurgical trainees across various domains using Likert scale-type questions. In the laboratory, maximum drilling temperatures adjacent to the drill hole were recorded and compared for the standard drill bit and the 30° and 45° conical drill bits and were not significantly different (p = 0.631 and p = 0.326, respectively). The maximum temperature recorded directly underneath the drilling site for the 45° drill bit was significantly higher than the temperature of the standard drill bit (p = 0.043). The differences between the standard and 30° drill bits were not significant (p = 0.783). Upon cadaver testing, the drilling times with 30° and 45° conical drill bits were significantly longer than those with the standard drill bit (p = 0.036 and p = 0.002, respectively). Likert scale scores were significantly higher for the conical 30° (median [IQR] 4.7 [3.3-5]) and 45° (4 [2-5]) drill bits than for the standard drill bit (1.7 [1-2.5], p < 0.0001), indicating significantly better performance. Conical drill bits used as a "rescue" strategy allowed for an EVD catheter angular adjustment range 6 to 9 times greater than that for the standard drill bit and resulted in a zero inadvertent dural puncture rate. The 30° conical drill bit can be safely used on its own or as a rescue tool to potentially achieve improved confidence, visualization, targeting, and precision of EVD placement while essentially eliminating the possibility of unintentional dural puncture with minimal increase in the total procedure time.

Analysis of Critical Wear Phenomena and Stress Induced in WC–Co-Based Twist Drill Bits Used for Drilling Hard Rock

Analysis of Critical Wear Phenomena and Stress Induced in WC–Co-Based Twist Drill Bits Used for Drilling Hard Rock

Analysis of drilling behavior of flax/PP composites

ABSTRACT The current research investigation aims to use and compare three different population-based optimization approaches to optimize the operating factors of drilling process to reduce thrust force (TF) and subsequently delamination in flax/PP laminates. Five different tool point geometries and three levels of spindle speed (SS) and feed rate (FR) were considered. Analysis of variance indicated that drill point geometry was most significant parameter affecting the TF, whereas SS had the most negligible impact. Moreover, the lowest and maximum TF and delamination factor (DF) were recorded for the U-shape drill bit and 135°- point angle twist drill bit, respectively. The outcome of the experimental investigation revealed that a low FR value (0.05 mm/rev) and medium-range SS value (1500–1800 RPM) were optimum parameters for each drill geometry. Although all optimization techniques provided almost the same optimum values, but TLBO (teaching learning-based optimization) technique’s convergence rate was fast compared to others.

Influence of Drilling Parameters on the Delamination and Surface Roughness of Insulative-Coated Glass/Carbon-Hybrid Composite

Drilling in synthetic fiber-reinforced polymer composites is facing challenges due to their anisotropic, inhomogeneity, and abrasive machining behavior. The joining of composite parts using fasteners is commonly done by the drilling, and the generated heat is one of the main causes to damage the drilled hole in the composite. Moreover, the quality of drilled hole is crucial for joining parts effectively. The paper presents the design, fabrication, and drilling of a hybrid fiber-reinforced polymer (HFRP) based on insulative coating. These composites were fabricated using vacuum infusion molding (VIM) and coated with different thicknesses to investigate the influence of drilling parameters and associated damages. Cutting speed, feed rate, and coating thicknesses were varied, and a full factorial design of the experiment was formulated. High-speed steel (HSS) twist drill bit was used to drill the coated composite and test samples, and delamination factor and surface roughness were measured. ANOVA and full factorial response optimizer were used to evaluate the influence and optimum drilling parameters. The delamination factor (DF) at the entry and surface roughness were found to decrease with the increasing cutting speed. However, the DF at the exit showed the opposite. Coating thickness influenced the delamination at the entry whereas delamination at the exit has been found insignificant. For drilling HFRP composite with 1 mm coating thickness, 3000 RPM spindle speed and 0.08 mm/rev feed rate were found optimum parameters in minimizing surface roughness and delamination damage. However, 6000 RPM and 0.02 mm/rev were found optimum parameters for drilling HFRP composite with 1.5 mm coating thickness.

Machining of aluminium 6063 alloy using high strength steel and titanium nitride novel coated drill tool using CNC and comparing the material removal rate

This study compares two tools, HSS M42 and TiN Coated twist drill bits, in order to determine which tool has the better material removal rate (MRR). Drill bits were of high speed steel (HSS M42) tool and use of Novel coating of Titanium Nitride on HSS tool in this study. The machining is done on a experimental specimen made of aluminium alloy AA6063. The material removal rate of both tools is measured in CNC drilling on two sets of 20 specimens each. Spindle speed, depth of cut, and feed were all controlled variables. G power 80% used for calculating sample size. SPSS software was used to record and analyse the results for both tools. The average MRR recorded for HSS M42 tool was 14.9803 mm3/s with a Standard deviation value 1.713221. This study has a significance value of 0.037 (p < 0.05) with a g power of 80%. The titanium nitride coated tool had an average MRR of 20.06995 mm3/s and 1.179870 standard deviation. The results were achieved at 0.037 significance, that is lower than 0.05. The titanium nitride coated drill bit has comparatively better MRR than the high speed steel drill bit in no-lubricant and no-coolant drilling circumstances, as per this study.

Analyzing the Potential of Drill Bits 3D Printed Using the Direct Metal Laser Melting (DMLM) Technology to Drill Holes in Polyamide 6 (PA6).

Drilling with standard twist drill bits is the most common method to create cylindrical holes. With the constant development of additive manufacturing technologies and easier access to additive manufacturing equipment, it is now possible to design and fabricate solid tools suitable for various machining applications. Specially designed 3D printed drill bits seem more convenient for standard and nonstandard drilling operations than conventionally made tools. The study described in this article aimed to analyze the performance of a solid twist drill bit made from steel 1.2709 using direct metal laser melting (DMLM), which was compared with that of a drill bit manufactured conventionally. The experiments involved assessing the dimensional and geometric accuracy of the holes made by the two types of drill bits and comparing the forces and torques occurring during the drilling of holes in cast polyamide 6 (PA6).

Comparison of HSS (M35) and CrN tool performance in CNC drilling operation of AA3003-H14 material to maximize the material removal rate

• The performance comparison of HSS (M35) coated tool and CrN coated tool to improve material removal rate in the drilling of AA3003-H14. • Material removal rate of the drilled specimens are calculated without compromising the roundness quality, roundness error percentage is measured using imageJ software. • Statistical Analysis performed using SPSS software to check the significance value of obtained results. • Within the limits of this study, CrN coated tool performance was better compared to HSS (M35) in aspect of Material Removal Rate and Roundness Quality. The performance comparison in HSS (M35) tool and CrN tool coating to improve material removal rate in the drilling of AA3003-H14 plates as base material during the CNC drilling operation. In this study HSS M35 and CrN coated twist drill bits are used. Aluminum Alloy 3003-H14 is the specimen in which drilling operation is done. This study includes two groups of 20 specimens each in which drilling operation is done with both the tools. Spindle speed, feed and depth of cut were input factors as 2200, 200 and 10 respectively. On comparing the Material removal rate of AA3003-H14 after drilling done by HSS (M35) and CrN at speed and feed of 2200 and 200 is 165 and 190 respectively. Roundness error with HSS M35 and CrN twist drill tool were 0.0110 and 0.0074 respectively. The results were calculated and analyzed by SPSS software. The significance value obtained for both experimental and control groups was 0.006 (p < 0.05) for material removal rate and 0.019 (p < 0.05) for roundness error. Within the limits of this study, Material removal rate values are observed high in the CrN coated tool compared with the HSS M35 tool for the same input speed, feed and depth of cut without compromising the roundness quality.

Drilling Strategies to Improve the Geometrical and Dimensional Accuracy of Deep through Holes Made in PA6 Alloy.

This article shows how different drilling strategies may affect the geometrical and dimensional accuracy of deep through holes. The tests were conducted on a three-axis direct-drive turning center. The holes were drilled in cylindrical PA6 aluminum alloy specimens 30 mm in length and 30 mm in diameter using 6 mm Ø VHM HPC TiAlN-coated twist drill bits. The cutting fluid was supplied to the cutting zone through the spindle. The experiments involved applying three strategies to drill deep through (5D) holes. The first required the workpiece to be fixed and the tool to perform both rotary and reciprocating motions. The second assumed that the workpiece performed the primary (rotary) motion whereas the tool moved in reciprocating motion. In the third strategy, the workpiece and the tool rotated in opposite directions and the tool also performed a reciprocating motion. The straightness, roundness, cylindricity, and diameter errors were the key output parameters in the analysis of the geometrical and dimensional accuracy of holes. The Taguchi orthogonal array design of experiment (DOE) was employed to determine the effects of the input (cutting) parameters (i.e., spindle speed and feed per revolution) and the type of hole making strategy on the hole errors by means of multi-factor statistical analysis ANOVA. The use of the highest spindle speed (n = 4775 rpm), the highest feed per revolution (fn = 0.14 mm/rev) and strategy I resulted in the lowest values of the output parameters (STR = 22.7 µm, RON = 8.6 µm, CYL = 28.2 µm, and DE = 9.9 µm). Strategy I was reported to be the most effective for hole drilling in PA6 aluminum alloy because, irrespective of the values of the process parameters used, three out of four output parameters, i.e., straightness, roundness and diameter errors, reached the lowest values.

Hole Quality Observation in Single-Shot Drilling of CFRP/Al7075-T6 Composite Metal Stacks Using Customized Twist Drill Design

In the modern aircraft manufacturing industry, the use of fiber metal stack-up material plays an important role. During assembly, these stack-up materials need to be drilled, and single-shot drilling is the best option to avoid misalignments. This paper discusses hole quality in terms of hole edge defects and hole integrity with respect to tool geometry. In this study, tungsten carbide (WC) twist-type drills with various geometric features were fabricated, tested, and evaluated. Twenty custom twist drill bits with primary clearance angles ranging from 6° to 8°, chisel edge angles from 30° to 45°, and point angles from 130° to 140° were fabricated. The CFRP and Al 7075-T6 were stacked up, and a feed rate of 0.05 mm/rev and spindle speed of 2600 rev/min were used for all drilling experiments. The experimental array was constructed using response surface methodology (RSM) to design the experiments. The impact of factors and their importance on hole quality were investigated using analysis of variance (ANOVA). The study demonstrates that the primary clearance angle, followed by the chisel edge angle, is the most important factor determining hole quality. As a function of tool geometry, correlation models between exit delamination and burr height were developed. The findings suggested that, within the range of parameters examined, the proposed correlation models might be utilized to predict performance measures. For drilling CFRP/AL7075-T6 stack material in a single shot, the ideal twist drill geometry was determined to be a 45° chisel edge angle, 8° primary clearance angle, and 130° point angle. For optimum drill geometry, the discrepancy between the expected and actual experiment values was 0.11% for exit delamination and 9.72% for burr height. The findings of this research elucidate the relationship between tool geometry and hole quality in single-shot drilling of composite-metal stacks, and more specifically, they may serve as a useful, practical guide for single-shot drilling of CFRP/Al7075-T6 stack for the manufacture of aircraft.

Comparative Analysis in Drilling Performance of AA7075 in Different Temper Conditions

The widespread use of heat treatable7075 aluminum alloy in the aerospace industry requires a high machinability performance. The main objective of this study is to examine the machinability and the surface quality conditions of the AA7075 material with different temper conditions. For this purpose, various temper treatments are implemented to evaluate the impact of microstructural properties on tool wear and the surface quality of the drilled holes. The drilling operations have been done on O, F, T4, T6, and T7 temper conditions. Process parameters were three different spindle speeds (715, 1520, and 3030 rev/min) and three feed rates (0.1, 0.2, and 0.3 mm/rev) with HSS-G high-performance ground standard twist drill bit. The present work deals with the effects of temper conditions on thrust force, drilling temperature, tool wear, surface integrity, and chip morphology. Response surface methodology was used in the evaluation of experiment results. The optimization results showed that while thrust force and torque are not significantly affected by a change in spindle speed, they are sensitive to an increase in feed rate. Heat-generation on the drill bit is the lowest at low levels of both the feed rate and spindle speed parameters. The AA7075-T6 condition specimen was machined with continuous chip formation, resulting in the best hole surface quality. 3D Finite element modeling of the drilling process was carried out. Numerical analysis revealed the drilling performance of AA7075-T6 in terms of thrust, heat generation and chip formation.

Determination of twist drill bits wear: the effect of the composition and structure of the steels

Abstract The aim of the study was to relate the influence of the chemical composition, structure, and basic properties as hardness of the tested drill bits on resistance to their wear. The chemical composition of the drill bit was investigated using the electric excitation emission spectrometry method and EDS microanalysis. Metallographic specimens were prepared and observed to determine the structure of each tool. Hardness tests were carried out on the shank and the working part of the tools. Material wear tests were carried out on the basis of measuring the wear of the drill bit flank. It has been shown that the appropriate selection of the chemical composition and heat treatment has a significant impact on the wear resistance of cutting tools, which directly translates into their quality.

Enhancement of Deep Drilling for Stainless Steels by Nano-Lubricant through Twist Drill Bits

This paper represents a new lubricant method which is able to one-stroke drill deep holes with a length-to-diameter of 8, on the AISI SUS 304 stainless steel. By adding graphene nanosheet into typical soluble emulsion and then mixing with water, a nano fluid can be made. The results revealed that using nanofluid can provide a reduction of 4.4-fold of the drilling torque, and thus expand the tool life as many as 20 times, compared with using typical emulsion lubricant. The proper set of cutting parameters was found by using Taguchi L9 experiments as 550 rpm spindle speed and 0.05 mm/rev. The results can be expanded to apply in other deep drilling of hard-to-cut material, using inexpensive devices and avoiding peck-drilling. The proposed lubricant can also be promissing for other machining operations.