JPS6117768Y2 - - Google Patents

Description

[Detailed description of the invention] This invention relates to an improvement of a two-blade drilling tool.

Conventionally, the most common deep hole drilling tool is a single-blade drill with a single cutting edge. But recently,
In order to increase the feed rate in deep hole drilling (that is, to enable high feed rates), a two-blade deep hole drilling tool with two cutting edges has been developed.

As shown in Fig. 1, this two-blade deep hole drilling tool has two cutting blades 1a, 1 disposed symmetrically around the axis O _C at the tip of the tool body.
b, two untwisted blade grooves 2a, 2b located on the rake face side of each of these cutting edges 1a, 1b and provided along the axial direction of the tool body, and each of these blade grooves 2a, 2b. Two guide parts are located on the opposite side from the cutting blades 1a and 1b and are arranged symmetrically around the axis O _C at the tip of the tool body similarly to the two cutting blades 1a and 1b. 3a and 3b.

Here, the two guide parts 3a and 3b have the function of guiding the tool itself during drilling and the function of burnishing the inner surface of the hole _. Guide part 3
a, 3b and the distances to the respective cutting edges 1a, 1b were all made to have the same dimensions. Therefore, in the conventional type, when the feed rate is increased, the generated torque increases significantly, and there is an undeniable problem that high feed machining, which is a characteristic of two-flute blades, cannot be performed. This problem is particularly severe in materials with strong clamping forces, such as aluminum or cast iron, in which case the tool may break, resulting in extremely short tool life.

This idea was created in consideration of the above points, and by reducing the torque during drilling, high-feed machining can be performed effectively, and the tool life can be extended. This provides a two-blade drilling tool.

Hereinafter, the content of this invention will be explained in detail with reference to the attached FIG. 2.

In order to facilitate understanding of this invention, we will first discuss the points of view that led to this invention.
When drilling holes, a dimensional tolerance is set for the diameter of the drilled hole, such as ±5 μm for castings and −10 to −15 μm for aluminum. Therefore, within the allowable range of such dimensional tolerance, the two guide portions 3a,
It should be possible to make the outer diameter between the two cutting edges 3b slightly smaller than the outer diameter of the two cutting edges 1a and 1b. This idea was created as a result of various experiments based on this perspective.

That is, in the case of the two-blade drilling tool of this invention, as shown in FIG. The feature is that it is set small. The difference (l-n) between the two needs to be at least smaller than the absolute value of the permissible dimension value of the hole to be drilled, but if dimensional accuracy is not a big problem, it should be 0.003 mm or more.
By setting the diameter to 0.020 mm, particularly in the range of 0.003 mm to 0.010 mm, the effect of reducing the burnishing torque can be effectively obtained. In addition, 4a and 4b in the figure are body clearances.

As described above, in the two-blade drilling tool of this invention, the outer diameter between the two guide parts 3a and 3b is set smaller than the outer diameter of the two cutting edges 1a and 1b by a predetermined dimension. As a result, the torque applied to the tool during drilling can be reduced, resulting in the excellent effect that deep holes can be drilled at high speed. Of course, this effect is particularly large when processing materials with strong clamping force as described above. Note that the tightening that the tool receives from the hole is thought to be caused by the contraction of the workpiece after it expands due to cutting heat. By setting small, both guide parts 3a, 3
b can be brought into contact with the inner peripheral surface of the hole with appropriate pressure. Therefore, the cutting edge of the tool will not run out, and the guiding function of the guide portion 3a will not be impaired.

This idea can be applied to deep hole drilling tools, such as guide drills, to great effect, but other tools such as general two-blade drills, which require large drilling torque and high hole accuracy, are also effective. It can also be applied to drilling tools.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing a conventional example of this type of two-blade drilling tool, and FIG. 2 is a block diagram showing an embodiment of this invention. 1a, 1b...cutting blade, 2a, 2b...blade groove, 3
a, 3b...Guide part, O _C ...Axis center.

Claims (1)

[Claims for Utility Model Registration] 1. Two cutting blades arranged symmetrically around the axis at the tip of the tool body, and two cutting blades located on the rake face side of each of these cutting blades and arranged symmetrically around the axis of the tool body. Two untwisted blade grooves are provided along the center direction, and each of these blade grooves is located on the opposite side of the cutting edge, and is arranged symmetrically around the axis at the tip of the tool body. a two-blade drilling tool, characterized in that the outer diameter between the two guide parts is set to be smaller than the outer diameter of the two cutting edges by a predetermined dimension. 2. The two-blade drilling tool according to claim 1, wherein the value of the predetermined dimension is at least smaller than the absolute value of the allowable dimension value of the hole to be drilled. 3. The two-blade drilling tool according to claim 1, wherein the drilling tool is for deep hole drilling, and the predetermined dimension has a value of 0.003 mm to 0.020 mm.