• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 1997.04a
• /
• pp.1063-1067
• /
• 1997

A study of carbide step drill cutting ability is highly progessing the step drill with more then twice diameter rate is so difficult in regrinding and very easy to damage during machining. As the machining of step drill for closed hole is occur to breakage at small diamter poistion, so it is very difficult to machinine. Thue, in this experiment, We investance roundness and surface roghness by machining distance and were identifid that the first distance, 5~10m, was fine with 7 .mu.m but the arround of 15m was happened so much alternation. And we were indentified that after 20m was happend statable machining. The surface roughness was happened the same conditions. So application of stwp drill we think that the selection of cutting conditions need lots consideration and the study of step drill's diameter ratio ratio is carred out.

• Journal of the Korean Society for Precision Engineering
• /
• v.19 no.11
• /
• pp.183-191
• /
• 2002

Drilling tests were carried out using drills with various drill shapes for burr minimization. Final objective of this study is to develop compatible drill shape for minimization of burr formation. For experiments, general carbide drills, round drills, chamfered drills and step drills are designed and manufactured. Burrs are formed by various cutting conditions and in 4 different work materials. Laser sensor is used to measure burr geometries. Cutting forces in drilling are also measured and compared in every drill. As a result of the experiments, step drills with specific step angle and step diameter are suggested for burr minimization.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2002.05a
• /
• pp.1043-1046
• /
• 2002

In this paper, drill tests were carried out by modifying drill geometry for burr minimization. Final objective of this study is to develop compatible drill shape for minimization of burr formation. These experimented results with modified drill are measured with laser sensor after performing drilling with variable material. Simultaneously, the cutting force and the torque of various drill geometry have been observed with same cutting condition to judge drill stability. As a result, burr was minimized in step drill with 75$^{\circ}$ step angle at every material.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 1997.10a
• /
• pp.911-914
• /
• 1997

This Experiment was carried out for bur minimization in drilling. New drill geometries are proposed to minimize the burr formation in drilling operation. Three types of drills are made, champer, round and step drill. The burr formed in first cutting by front cutting edge ca be removed in second cutting by the cutting edges in chamfer, round edge and step. New burrs are formed by second cutting and can be minimized according to the change of drill geometry like, chamfer size and angle, corner radius in round drill and step size and angle in step drill. To measure the burr formed in drilling, laser sensor is used.

• Journal of the Korean Society for Precision Engineering
• /
• v.13 no.12
• /
• pp.46-53
• /
• 1996

Micro drilling is one of the most important machining types and its necessity becomes more and more increasing in the whole field of industry. Micro drilling, however, has few the case of practical application, because it requests high techniques : manufacturing micro drill, treating chip, producting precise hole shape and progressing machining effeciency. Micro drilling has a technical problem: drill breakage from the lack of drill rigdity and the interuption of chip. It is, therefore, essential to select the proper cutting conditions and the step fed for the method solving the lack of rigidity and the interruption of chip. Especially, step feed is very efficient to avoid the breakage of drill, but bring about reducing of cutting efficiency. The study on step feed must be requested more than the present in the near future. The purpose of this paper is to investigate experimentally about cutting conditions which affect on tools and round errors and to estimate about the effect of step feed as well as optimal step feed size to solve the breakage of drill.

• Journal of the Korean Society for Precision Engineering
• /
• v.17 no.10
• /
• pp.132-140
• /
• 2000

In conventional drilling, burr geometry can be changed according to the variation of drill geometry like point angle, rake angle. Step drilling is proposed to minimize the burr formation in drilling operation. The burr formed in first cutting can be removed in second cutting by the edge in step. The burr formed in second cutting by the edge in step can be minimized according to the change of geometry like, step angle and depth. The mechanism in step drilling is analyzed. Some step drills are applied to drilling the input shaft which is used for vehicle steering. To measure the burr formed in drilling, laser and height gage are used.

• Proceedings of the KSME Conference
• /
• 2007.05a
• /
• pp.1517-1521
• /
• 2007

On this study, technical aspects were reviewed to drill a series of micro holes (${\phi}$0.10) over 200 within a few micron tolerance in diameter and position on the stainless steel material. Dedicated tools & jigs were designed and manufactured and optimum cutting conditions were found. On this micro hole drilling process, guide drill and step feeding were applied to help chip discharge, prevent drill breakage and finally improve the accuracy of positioning and roundness. The processing results indicated that most holes are distributed within a few micron tolerance in diameter and position intervals.

• Journal of the Korean Society for Precision Engineering
• /
• v.23 no.9 s.186
• /
• pp.47-53
• /
• 2006

An Experiment was carried out to find the scheme far minimization of burr formation on inclined exit surface in drilling. Several drills with different geometry are used for drilling the workpiece with inclined exit surface. Step drills are specified with step angle and step size. The influence of the inclination angle of exit surface on burr formation was observed, which enables to analyze the burr formation mechanism on inclined exit surface. Along the edge on the inclined exit surface, burrs are formed by the bending deflection to feed direction and also burrs are formed in exit direction of cutting edge. To minimize the burr formed in feed direction, the corner angle which is formed by the inclination angle and step angle must be large enough not to be bent to burr. By decreasing step angle of drill and decreasing the distance between two axes of two holes, burr formation at the intersecting holes can be minimized. Burr formation mechanisms are analyzed according to the drill geometries and cutting conditions. Several schemes far burr minimization on inclined exit surface were proposed.

• Journal of Biosystems Engineering
• /
• v.40 no.1
• /
• pp.1-9
• /
• 2015

Purpose: The objective of this study was to understand the operating mechanism of the rock-drill drifter, to explain how to setup an experimental test system and measure the strain of the drifter's rod, and to evaluate the drifter's performance with respect to the impact energy and blow frequency. Methods: The structure of the rock-drill drifter and its operating principle regarding the impact process were analyzed. Static calibration was carried out to calculate the correction factor using a drifter rod as the first step of the experimental test. The impact energy and blow frequency were then calculated based on strain measurements of the drifter's rod. Results: Experimental results showed that the tested drifter elicited a blow frequency of 3330 BPM (Blows Per Minute) and generated impact energy of 170 J/blow. This indicates that the drifter elicits a higher percussion speed and results in a lower impact energy compared to the hydraulic breaker at the same input power. Conclusions: The study proposed methodologies that deal with the experimental setup and the evaluation of the performance of the rock-drill drifter. These methodologies can be extensively used for validating and improving the percussion performance of the drilling equipment.

• Journal of the Korean Society for Precision Engineering
• /
• v.6 no.3
• /
• pp.24-31
• /
• 1989

By use of the machining center, step-feed drilling was operated under the variety of conditions as to materials, tools and cutting conditions. Based on this study the following conclusions can be drawn : 1) The cutting force can be diminished by utilizing the step-feed working; specially the most effective was it for the brass among the carbon steel, the brass, and the cast iron. 2) Tool life can be enlarged more than double when three-step-feed working is used. 3) For the constant cutting-depth(30mm), the most optimal number of stepping is 3.