Fast drilling of small-diameter holes by core flat drills

Attention focuses on the fast drilling of small-diameter holes by core flat drills, hard-alloy drills, and unidirectional drills with the supply of working fluid to the cutting zone. Means of improving the productivity are discussed. The best approach to drilling small-diameter holes is outlined.     

Optimizing the high-speed drilling of small-diameter holes by core flat drills

A model is developed for optimization of the high-speed drilling of small-diameter holes by core flat drills. Thanks to the structure of the model, the problem reduces to optimization of the process under constraints associated with optimization of the bit’s structure and geometry.     

Investigating the feasibility of DLC-coated twist drills in deep-hole drilling

The ideal coating for twist drills used to drill deep holes should have both a high hardness and a smooth surface. The latter property is considered to ease chip evacuation through the drill’s chip flutes and, therefore, reduces the risk of chip clogging and possible premature drill fractures. For this reason, diamond-like carbon (DLC) appears to be a well-suited type of coating. This paper presents the results of cutting tests using DLC-coated HSS and cobalt-HSS twist drills when drilling deep holes of diameter 1.5 mm into plain carbon steel. Their capability to extract swarf from the borehole as well as their tool lives were investigated and compared to uncoated and TiN- and MoS₂-coated drills. Although the DLC-coated drills showed a very good swarf disposal capability, they did not exhibit a longer tool life when compared to off-the-shelf drills.     

钻孔夹具设计

笔者设计的夹具用于钻床上加工斜孔及倾斜台阶面,是一种摆动式钻床专用夹具。通过分析夹具的结构特点、工作原理,计算定位误差、夹紧力、导向误差,说明该夹具设计新颖、结构合理、效率高,同时,还解决了斜孔和斜面加工精度和位置难保证的难题。     

涂层钻头钻削碳纤维复合材料的轴向力研究

不同刀具材料对碳纤维复合材料的加工有较大的影响。通过合理选择钻头的基体材料和涂层材料,基于正交试验综合分析不同涂层材料、主轴转速及进给速度对钻削轴向力的影响。试验结果表明,涂层材料对轴向力的影响最大,涂层钻头的钻削轴向力比无涂层YG6X钻头小很多,类金刚石涂层(DLC)钻头最小。TiAlN和TiCN涂层钻头都有不同程度的磨损,DLC钻头的耐磨性和加工质量都远远高于其他涂层。     

Production accuracy of holes in ultrasonic drilling

The production accuracy obtainable for ultrasonically drilled holes is affected by the continuous wear of the abrasive particles in the slurry and by tool wear. The influences of certain important parameters such as static load, machining time, type of abrasives, grit size and work material on dimensional and form accuracy are presented.     

Machinability of green titanium powder compacts during drilling using HSS twist drills

The poor machinability of titanium-based alloys has until now been addressed by either choosing a suitable tool material, management of the heat generated     

Electrochemical drilling inclined holes using wedged electrodes

This paper presents electrochemical machining of inclined holes using wedge-shaped electrodes. Numerical simulation has been carried out to study the initial flow fields of the machining area with and without the wedged tip at different machining inclination angles. Experiments were conducted consequently to study the machining characteristics affected by each flow field distribution mentioned above. Theoretical and experimental analyses indicate that inclined hole machining using wedged electrodes distributes the electrolyte flow more uniformly and hence leads to a more stable machining process. Wedged electrodes could be used in electrochemical drilling to efficiently drill high-quality holes with large inclination angles.     

Thermoelastic stress analysis of oblique holes in flat plates

The stresses in the region of an oblique hole in a flat plate are analysed using the thermoelastic stress analysis technique. Particular attention is given to the obliquity of the hole and to the line of action of the applied load in relation to the hole axes. The effects of varying plate thickness are also studied. The data from around the rim and along the internal axis of the hole are presented as a series of stress concentration factors. The results are compared to those from previous studies and discussed in detail. These confirm the findings of the previous work in that increases in hole obliquity increase the stress at the hole, the maximum principal stress is obtained when the load is applied normal to the major axis of the surface ellipse and that as the thickness of plate increases the stresses on the surface of the plate decrease. Issues such as differences in the material’s Poisson’s ratio value are also discussed. The effect of any non-adiabatic behaviour on the thermoelastic output is described.     

基于正交试验的麻花钻钻削钛合金的刃磨参数选择

麻花钻是孔加工的重要工具之一,钻头的快速磨损制约着孔的加工质量和加工效率.基于产品抽样钻孔试验和正交试验,对高速钢麻花钻钻削钛合金的刃磨参数进行了综合分析,探讨了在不同顶角下切屑槽的有无对钻削过程的影响.试验结果表明,切屑随着顶角的增大,断屑越容易;在横刃两端开切屑槽能够减小轴向力,并有利于防止刃带的磨损,提高加工效率.     

利用普通钻床或铣床加工高精度坐标孔

提供了一种用普通钻床加工高精度坐标孔的方法。提出了联合使用量块和一套导向镗孔装置的解决方案。     

整体硬质合金枪钻在特深小孔钻削中的应用

本文分析了特深小孔及其钻削特点,对研制特深小孔钻床和钻头提出了一系列技术要求,并介绍了使用时的钻削参数,同时指出了钻削加工中应注意的几个技术问题。     

Influence of inclined holes in measurement of residual stress by the hole drilling method

The hole drilling method is widely used in measuring residual stress in surfaces. In this method, the inclination of holes is one of the sources of error. This paper presents a finite element analysis of the influence of inclined holes on the uniaxial residual stress field. The error in stress has been found to increase proportionally to the correct inclined angle of the hole. The correction equations by which one may easily obtain the residual stress, taking account of the inclined angle and direction, have been derived. The error of stress due to the inclined hole has been reduced to around 1% using the correction equations.     

Performance of cryogenically treated M35 HSS drills in drilling of austenitic stainless steels

In this study, performance of cryogenically treated M35 high speed steel (HSS) twist drills in drilling of AISI 304 and 316 stainless steels was evaluated in terms of thrust force, surface roughness, tool wear, tool life, and chip formation. To present the differences in tool performance between untreated and treated drills, and machinability between AISI 304 SS and AISI 316 SS, a number of experiments were performed at different combinations of cutting speed, and feed rate. As the results of the conducted experiments, the treated drills showed better performance than untreated drills in terms of thrust force, surface roughness, and tool wear and tool life for both types of stainless steels. Tool lives of treated HSS drills in drilling of AISI 304 SS and AISI 316 SS improved 32% and 14%, respectively, when compared with untreated drills. Experimental results also showed that machinability of AISI 304 SS was harder than the machinability of AISI 316 SS.     

在普通立钻上加工板类工件的精密孔系

提出一种在普通立钻上用模板找正加工板、盘类工件上孔系的工艺方法