JP3204239U - Diamond tool for drilling - Google Patents

Abstract

To provide a core drill for deep hole drilling capable of improving straightness accuracy and increasing grinding efficiency. In a core drill for deep hole machining, an intermittent build-up part 5 having the same dimension as the diameter of the drill tip is provided on the neck 2 which is narrowed by one step following the metal bond grindstone 1 at the tip of the drill. In this case, the bending of the neck portion is prevented, and the intermittent build-up gap has a structure that serves as an anti-vibration grip portion for the core drill when the deep hole processing machine is mounted, and also serves as a grinding fluid and facet discharge passage in the processing hole. [Selection] Figure 2

Description

  In the present invention, in the drilling of the brittle material, the straightness becomes worse as the depth L becomes larger than the hole diameter D. The present invention relates to a drilling tool that improves the straightness.

  Conventionally, when drilling a brittle material, a processing method similar to gun drilling is employed, and a core drill is used. However, as the hole diameter D decreased and the depth L increased, the straightness deteriorated, and there was no one that could pursue accuracy as a geometrical tolerance.

  Even if the geometrical tolerance is not satisfied, the repeatability is stable to some extent, so that the distance between holes can be considerably reduced. For this reason, even if a large number of holes are opened in a staggered or grid pattern, the boundary walls remain without penetrating adjacent holes, each becoming a single hole, which is recognized to some extent as processing.

  It is necessary to pay attention to the relationship with the workpiece standard because the straightness is poor even if the positional relationship between holes is not a problem. For example, when a through-hole is drilled in a square pillar having a length L, it is normal that the exit is out of the center position even if the processing entrance is located at the center of the square.

  The amount of positional deviation depends on the grinding resistance during drilling, and the amount of deviation increases in proportion to the increase in grinding resistance. Naturally, as L / D increases, the amount of deviation also increases. The deviation direction also depends on the posture during machining and the core drill axis direction. When the square pillar is laid down sideways, the exit hole position is located above the center, and the amount of misalignment on the left and right depends on the direction of rotation of the drill, and on the right side is the left side. When machining with a square pillar upright, the deviation direction depends on the tool characteristics and shows almost the same tendency with the same tool, but when the tools are different, the bending direction becomes different and the deviation direction tends not to be constant.

  Japanese Patent Application No. 2009-141990   Japanese Utility Model Publication 62-122121   Shokai 63-127877

  Unitac Corporation Catalog Double Tube System   Hitachi Metals Technical Report Vol. 26 “Improvement of drill structure for micro deep hole drilling and its effect”

  In the metal processing, when the hole depth L exceeds 10 times the diameter D, deep hole processing is performed. Moreover, it is reported that L / D can be 10 to 100 in the metal working technology report. On the other hand, in the deep hole processing of a brittle material, a core drill is used and processing with an L / D of 200 to 300 has already been performed. Although deeper machining is possible, machining accuracy and straightness become problems, and in order to improve accuracy, it is necessary to extremely reduce the machining speed. A core drill that improves the straightness and increases the processing speed is provided.

  The core drill shape for deep holes is composed of an additional steel pipe portion that serves as a joint portion from the tip to a metal bond grindstone portion, a hollow stainless steel pipe neck portion, and a tapered shank. The hole diameter is the outer shape of the metal bond grindstone part, the grinding remaining at the center part, and the core diameter is determined by the grindstone inner diameter. The neck outer diameter is smaller than the grindstone outer diameter, and the inner diameter is larger than the grindstone inner diameter. The processable depth is determined by the neck length. For the neck pipe, a ready-made product is generally used.

  The grinding fluid passes through the rotary joint, shank, and neck pipe, and is supplied to the grinding section and the tip of the metal bond grindstone at high pressure. Therefore, a clearance is required between the neck outer shape and the hole, and the neck inner diameter and the core.

  This gap causes the hole geometrical tolerance and straightness to deteriorate. When the diameter of the grindstone is increased, the neck pipe can be made rigid. However, when the diameter is 2 mm or 1 mm or less, for example, the length is 300 mm, the neck is bent due to the grinding pressure. This bending affects the grinding pressure at the tip of the grindstone, and as a result, the hole is bent.

  The amount of bending is affected by the gap. Since the bending amount itself is superimposed as the drilling progresses, the bending amount naturally increases as the drilling depth increases even in a small gap. This bending direction is affected by gravity when horizontal machining is performed with a core drill. The deflection of the neck may be considered as a pin-fixed beam, and as a result, the grinding surface pressure increases below the core and the drilling direction is upward. However, since the drill is rotating, the deflection direction is slightly changed and the displacement direction is also changed depending on the rotation direction.

  When vertical machining is performed with a core drill, bending of the neck due to gravity is eliminated. However, it can be considered in the same way as the buckling due to the vertical load of the column. If the external environmental conditions are the same, the buckling direction is the same as the individual difference of the column, and the bending direction in the elastic region, which is the previous stage of buckling, also becomes the individual difference, so the bending direction is fixed by the drill.

  If this neck bending is eliminated, it is possible to easily estimate that the grinding pressure can be increased under the best conditions for grinding and the drilling efficiency is increased. Therefore, it is an important requirement that the neck does not bend even if the grinding pressure is increased.

  A drill is generally used when drilling in metal. Straight shank is normal, but the maximum possible machining depth is the length of the twisted part. If it is pushed into the shank part, it will not be possible to discharge the facet and supply / discharge the cutting fluid. In the case of a straight shank, the tip diameter with a cutting edge, the twisted part, and the shank part have the same thickness and can be drilled with extremely high rigidity and good straightness. Even in this case, if the discharge of the facet is not successful, it has been reported that the straightness is deteriorated, and it can be said that the discharge of the facet is important.

  When metal processing is applied to brittle material processing, the neck thickness is the same as the diameter of the metal bond grindstone, but it can be seen that a structure that facilitates the discharge of the grinding fluid and the face is sufficient. The double tube system has a similar structure. However, it is easily conceivable that the entire region of the neck portion does not have to be the same as the grindstone diameter. Considering the neck cross-section and the center position of the circle, the center position of the circle is determined if three points are determined, and therefore the neck position is determined if three or more points are touched to the hole wall. The contact support points are provided at equal intervals in the core drill axis direction, or the positioning function is exhibited even with a continuous mountain like a spline shaft.

  If the length of the core drill is increased, the tip end will be shaken and the machining cannot be performed only by gripping the shank as in conventional drilling. For this reason, a long gun drilling machine has been proposed. Similarly, in the core drilling process, a processing machine including a rotation drive unit, a grinding fluid supply rotary joint unit, and a shake prevention gripping unit is used. The shake prevention gripping part is divided into a tip support and an intermediate support part, and the number and position of intermediate supports are determined by the length of the core drill. This support is moved in place with the drilling operation.

  It is preferable that the amount of core drill protrusion from the tip support portion for preventing vibration is small. This is because as the protrusion amount increases, the deflection increases and the accuracy of the position of the drilling entrance is also involved. In the initial stage of machining when the workpiece, which is the work material, contacts the tip of the core drill, the workpiece and the tip of the drill do not uniformly contact at the same time. When drilling is advanced in this state, the runout is restrained and settled by the hole, but the entrance position accuracy is deteriorated. Therefore, in the initial stage of machining, a small amount of step machining is preferable to prevent center runout.

  When the core drill is stabilized and drilling progresses in a small amount of step machining, the process moves to a quantitative step machining process. In fixed step machining, the rotation of the core drill is stopped and the positional relationship with the workpiece is also maintained. Unscrew the gripping mechanism of the shake prevention support part and move it to the drill drive side. As a result, the amount of protrusion of the drill tip increases by a fixed dimension, and this fixed dimension becomes the next drillable dimension. This is repeated and deep hole machining is performed.

  FIG. 1 shows a conventional core drill. FIG. 2 shows a core drill according to the present invention. The diameter of the built-up portion of the core drill is the same as the diameter of the tip of the drill, thereby preventing the bending of the drill neck. Since bending is prevented, a machined hole with good straightness can be obtained regardless of the workpiece mounting and drilling posture during machining.

  FIG. 3 shows a cross-sectional shape of the built-up portion. The build-up notch serves as a discharge passage for the grinding fluid and the facet. It is desirable that the passage cross-sectional area be larger than the gap area between the unground core and the neck inner diameter so as not to increase the outflow resistance.

  General overlay welding and thermal spraying can be considered as the overlaying means. Plating can be considered when the base metal thickness is thin and is affected by heat. Diamond tool manufacturers use electrodeposition of abrasive grains, but the same method is considered possible.

  Although the posture inside the hole is supported by the built-up portion, when it is mounted on a machine and rotated at a high speed, the conventional support position or support method may interfere with the built-up portion and cause a centering failure. In the case of the core drill shown in FIG. 2, it is necessary to change to a system that holds the neck portion other than the built-up portion.

  FIG. 4 shows a development view of the neck. The built-up portion has a circumference divided into three equal parts, and has a spline shaft shape. Basically, various uneven shapes may be considered as long as there is a groove support portion for preventing bending of the shaft, a space for discharging the grinding fluid and facets, and grooves. If it is possible to use a thick pipe, a method of processing a wide groove instead of building up can be considered.

  It is necessary to select whether the groove support or the build-up support is good as a holding method in the machine according to the core drill specification. In the specification shown in FIG. 4, the pipe is held and supported while avoiding the spline protrusion.

  Parts that have been subjected to advanced processing on brittle materials are often used in the manufacturing process of electronic parts, and optical fiber is also used as a means for improving transmission efficiency. Expected to be used in these fields.

Conventional core drill diagram Core drill diagram related to the present invention Core drill AA 'sectional view Core drill neck development

DESCRIPTION OF SYMBOLS 1 Metal bond grindstone part 2 Neck part 3 Additional steel pipe part 4 Connecting screw part 5 Overlaying part

Claims (1)

  In deep hole drilling core drills, an intermittent build-up part that is the same size as the drill tip diameter is provided on the narrowed neck part following the metal bond grindstone at the tip of the drill, and the neck part is bent by following the processed hole. A tool having a structure in which the intermittent build-up gap serves as an anti-vibration gripping portion of the core drill when mounted on a deep hole machining machine and serves as a grinding fluid and facet discharge passage in the machining hole.

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