JP2011177815A - Rotary tool bit and method for manufacturing rotary tool bit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enhance entire surface hardness and abrasion resistance by providing a soft core body having the hardness lower than that of a hardened layer on the inner side of the hardened layer formed on an entire bit surface by executing a plasma carburization treatment, to prevent any local stress concentration by covering the bit with the hardened layer of a closed structure and forming the inner soft core body to be a cushion, and to form the hardened layer at an adequate depth so as to leave the soft core body therein through the plasma carburization treatment. <P>SOLUTION: A rotary tool bit 1 subjected to the carburization treatment includes a hardened layer 2 formed by executing the plasma carburization treatment on the entire bit surface S, and a soft core body 3 located inside the hardened layer 2 and having the hardness lower than that of the hardened layer 2. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to a rotating tool bit such as a driver bit or a drill bit that is detachably attached to a rotating tool such as an electric tool or an air tool, and a method of manufacturing the rotating tool bit.

2. Description of the Related Art Conventionally, there is known a rotary tool bit that is a long tool piece that can be attached to an anvil portion connected to a drive shaft of an electric tool or an air tool.
The rotary tool bit has a tool cutting edge (cutting edge portion) on one end side thereof, and a shank that is fitted in the anvil portion of the rotating tool and receives a rotational force from the rotating tool at the middle portion thereof. Is provided with an engaging portion into which the locking member of the anvil portion is fitted.

Further, the conventional rotary tool bit has a twistable band with a small cross-sectional area in the circumferential direction of the shank, that is, a locking circumferential groove constricted in the middle of the shank. When the rotational torque is applied, the bit is twisted, the excessive load applied to the bit is absorbed, and the impact is alleviated, thereby extending the life of the bit for the rotary tool.
As a conventional technique that corresponds to the problem of rotational torque absorption and shock relaxation, there is one described in Patent Document 1 below.

The driver insert described in Patent Document 1 can be tempered later, cooled by liquid, or individualized with a soft material and another hard material to form a twistable band. Extends life.
On the other hand, in order to extend the life of the bit, there is a technical means for depositing or ion plating an alloy such as titanium on the surface of the bit.

Japanese National Patent Publication No. 8-504585

However, the two technical means described above have the following problems.
As described in Patent Document 1, in the case of partial hardness adjustment by tempering or liquid cooling, it is almost possible to appropriately adjust the depth of the hardened layer in a thin portion such as a blade at the tip of the driver. Can not. Further, even when two materials having different hardnesses are individualized, there is a possibility that the material may fall off due to excessive load or impact during rotation.

In addition, when vapor deposition or ion plating is performed, the alloy between titanium and the metal material of the bit has poor adhesion due to the different connection between the particles, and the alloy layer falls off the bit surface, especially during impactful rotary tightening. There is a problem.
Furthermore, wear deformation occurs in the bit surface portion that comes into contact with an object such as a screw hole, and once the deformation occurs, stress is repeatedly concentrated on that portion, which causes the bit life to be shortened in an accelerated manner.

  In view of these points, the present invention has a soft core having a hardness lower than that of the hardened layer on the inner side of the hardened layer formed by subjecting the entire surface of the bit to plasma carburization, thereby reducing the surface hardness of the bit. While improving the wear resistance, the soft core in the hardened layer that is entirely covered is used as a cushion to prevent local stress concentration, and it can be adjusted to the appropriate depth of the hardened layer by plasma carburizing treatment. The object is to provide a possible bit for a rotating tool.

  In addition, the present invention provides a soft core having a lower hardness than the hardened layer inside the hardened layer formed by subjecting the entire surface of the rotary tool bit to plasma carburizing treatment, so that the bit is entirely formed of the hardened layer. An object of the present invention is to provide a method for manufacturing a bit for a rotary tool that can be covered, improves surface hardness and wear resistance, prevents local stress concentration, and adjusts a hardened layer to an appropriate depth. To do.

In order to achieve the above object, the bit for a rotary tool according to the present invention employs the following technical means.
The first is a bit for a rotating tool that has been subjected to carburizing treatment,
It has a hardened layer formed by subjecting the entire surface of the bit to plasma carburization, and a soft core that is located inside the hardened layer and has a hardness lower than that of the hardened layer.

Second, the bit blade edge portion is characterized in that a soft blade body that is continuous with the soft core body inside the hardened layer and has a hardness lower than that of the hardened layer remains.
Thirdly, it is a bit for a rotating tool that has been subjected to carburizing treatment,
At least the bit blade edge portion has a hardened layer formed by subjecting the surface to plasma carburizing treatment,
A soft blade body that is located inside the hardened layer and has a hardness lower than that of the hardened layer is left in the bit cutting edge.

Fourth, the depth from the surface of the hardened layer is 10 μm or more and 100 μm or less.
Due to these features, by providing a soft core with a lower hardness than the hardened layer inside the hardened layer formed by plasma carburizing treatment on the entire surface, the bit material and carbon are firmly connected, and the surface hardness and resistance The entire rotary tool bit can be wrapped with a hardened layer while improving wear. Therefore, the impact applied to the bit blade edge part etc. is received by the entire hardened layer, and the impact relaxation using the internal soft core as a cushion can be realized, and at the same time, the generation of local stress can be suppressed, By the plasma carburizing treatment, the hardened layer can be formed at a depth (thickness) from an appropriate surface that leaves a soft core inside.

  In addition, by leaving a soft blade body that is continuous with the soft core inside the hardened layer and has a lower hardness than the hardened layer at the bit edge, the hardened layer can be applied to thin parts such as blades at the tip of the driver and the tip edge of the drill edge. Therefore, the soft blade body can be left inside the thin bit cutting edge portion, and the impact applied to the bit cutting edge portion can be mitigated by using the soft blade body as a cushion. That is, it is possible to prevent breakage of the cutting edge, increase the durability of the bit cutting edge, and extend the life of the entire rotary tool bit.

  Furthermore, the bit blade edge part is connected to the bit material and carbon at the bit blade edge part by leaving a soft blade body located inside the hardened layer formed by plasma carburizing treatment on the surface and having a lower hardness than the hardened layer. It is possible to adjust the depth of the hardened layer by plasma carburizing treatment in the thin part of the bit for the rotary tool while ensuring the hardness of the blade edge and improving the wear resistance. It will have a soft blade which becomes a cushion. Therefore, impact unique to the bit cutting edge can be mitigated, and the improvement in the durability of the bit cutting edge leads to a long life of the entire rotary tool bit.

And by forming the depth of the hardened layer to 10 μm or more and 100 μm or less, it becomes possible to harden only the surface of the blade edge even if the bit blade edge portion is thinned or downsized, and the size of the bit for the rotary tool , Variations in shape and the like can be increased to increase versatility.
In the method for manufacturing a rotary tool bit according to the present invention, the entire surface of the rotary tool bit is subjected to plasma carburization to form a hardened layer, and a soft core having a lower hardness than the hardened layer is left inside the hardened layer. It is characterized by that.

  As a result, by leaving a soft core having a lower hardness than the hardened layer inside the hardened layer formed by subjecting the bit surface to plasma carburizing treatment, the adhesion between carbon and the bit material is improved and the surface hardness is increased. Improves wear resistance and receives the applied impact on the entire hardened layer, and at the same time enables the impact relaxation by the soft core, suppresses local stress generation, and adjusts the depth of the hardened layer by plasma carburizing treatment. Achieving

  Furthermore, it is possible to prevent cost increase and complicated material management due to an increase in processes such as a process of forming a twistable band in the middle of the shank and a process of individualizing two or more materials.

According to the bit for a rotary tool according to the present invention, a soft core having a lower hardness than the hardened layer is provided inside the hardened layer formed by subjecting the entire surface of the bit to plasma carburizing treatment, and the surface hardness and wear resistance are improved. The entire hardened layer receives impact and uses the soft core as a cushion, so that local stress concentration can be prevented and an appropriate depth adjustment of the hardened layer can be realized by plasma carburizing treatment.
According to the method for manufacturing a bit for a rotary tool according to the present invention, by leaving a soft core having a lower hardness than the hardened layer inside the hardened layer formed by subjecting the entire surface of the bit for a rotary tool to plasma carburization, The bit can be entirely covered with the hardened layer, so that the surface hardness and wear resistance can be improved, and local stress concentration can be prevented, and the depth of the hardened layer can be adjusted appropriately.

(A) is side surface sectional drawing of the bit for rotary tools which concerns on 1st Embodiment of this invention. (B) is a front view of the bit for rotary tools. (C) is the sectional view on the AA line of a bit blade edge part. (D) is the BB sectional drawing of a connection part. (E) is CC sectional view taken on the line of a mounting part. (A) is side surface sectional drawing to which the bit blade edge part was expanded. (B) is a sectional view taken along line XX of the bit cutting edge. It is a side view of the manufacturing apparatus of the bit for rotary tools. It is side surface sectional drawing of the bit for rotary tools which concerns on 2nd Embodiment. It is side surface sectional drawing of the bit for rotary tools which concerns on 3rd Embodiment.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
1 and 2 show a rotating tool bit 1 (driver bit) according to a first embodiment of the present invention.
This rotary tool bit 1 is a both driver bit formed of low carbon steel (about HV300) and having tapered bit end portions 11 at both ends. Both bit end portions 11 have a round cross section and a small diameter. It is integrally connected to each end of the mounting portion 13 through the connecting portion 12 (see FIG. 1D). The mounting portion 13 is inserted and mounted in an insertion hole (anvil portion) of a holder of a rotary tool (not shown) such as an electric impact driver.

The mounting portion 13 is formed in a substantially regular hexagonal cross section (see FIG. 1 (e)), engages with an anvil portion having a substantially regular hexagonal cross section, and rotates integrally with the holder of the rotary tool to drive force. Tell 1
The driver bit 1 may be made of high carbon steel (about HV700), and the cross-sectional shape of the mounting portion 13 may be a polygon such as a rectangle other than a substantially regular hexagon.

The driver bit 1 is formed by integrally forming both bit end portions 11, a connecting portion 12, and a mounting portion 13 in the longitudinal direction (rotation axis L direction), and each bit end portion 11 has a leading end from the connecting portion 12 side. It is a straight ridge (or taper ridge) that tapers to the side.
The bit end portion 11 has a plus shape (see FIG. 1B) or a minus shape (No. 2 in the plus shape in FIGS. A predetermined length (1.5 mm to 2.0 mm) is provided.

A bit blade tip portion 4 having a four-blade shape (a flat plate shape in the case of a minus shape) is formed at the tip of the bit end portion 11, and the length of the bit blade tip portion 4 along the rotational axis L is The length of the bit end 11 is substantially half (about 1.0 mm).
The mounting portion 13 is formed in a square cross section, in the embodiment, a regular hexagon so that it can rotate integrally with the anvil portion.

As shown in FIG. 1, the driver bit 1 is plasma carburized on the entire surface S (the entire surface S), and a hardened layer 2 is formed on the bit surface S.
The depth D (thickness) from the surface S in the hardened layer 2 is formed to 10 μm or more and 100 μm or less by plasma carburizing treatment that can be adjusted to a very shallow depth (or very thin thickness). Moreover, the depth D of the hardened layer 2 may be preferably 15 μm or more and 50 μm or less, and more preferably 18 μm or more and 30 μm or less.

The hardness of the driver bit 1 is originally the hardness of the material constituting it (when made of low carbon steel, the Vickers hardness is about HV300, and for high carbon steel, the Vickers hardness is about HV300). The hardened layer 2 on the surface S is harder than the original material hardness (Vickers hardness is about HV900).
That is, the driver bit 1 has a hardened layer 2 on the entire surface S (or almost the entire surface S), and a soft core that is softer than the hardened layer 2, that is, has a lower hardness, inside the hardened layer 2. The body 3 (a part of the soft body 6) remains.

In particular, as shown in FIGS. 2 (a) and 2 (b), also in the bit cutting edge portion 4 of the driver bit 1, the thickness (depth D) of the cured layer 2 is overwhelmingly smaller than the thickness of the blade-shaped portion. It is possible to leave a soft soft blade body 5 inside 2.
The soft blade body 5 is formed continuously with the soft core body 3, and the soft blade body 5 and the soft core body 3 constitute a soft body 6. That is, the hardened layer 2 is formed on the driver bit 1 so as to cover the soft body 6.

In addition, when the hardened layer 2 is formed on the entire surface S of the driver bit 1, the hardened layer 2 having a completely closed structure covering the soft body 6 without gaps or holes is provided over the entire surface S. It will be.
As described above, the entire hardened layer 2 wraps the soft body 6 so that even if an impact is applied to the bit cutting edge 4 or the mounting portion 13, the impact can be received by the entire hardened layer 2. The soft core body 3 inside the hardened layer 2 acts as a cushion to alleviate the impact.

As a result, local stress can be prevented from occurring in the driver bit 1.
Furthermore, since the sufficiently thin hardened layer 2 is formed even in the thin portion of the bit cutting edge portion 4, the soft cutting blade 5 that remains soft inside the bit cutting edge portion 4 is left uniquely, and the bit cutting edge portion 4 itself reduces the impact. As a result, the durability of the cutting edge can be improved, and the life of the entire driver bit 1 can be increased.

The hardened layer 2 does not necessarily have to be formed on the entire surface S of the rotary tool bit 1 and is in contact with other members (screw head, anvil portion of the rotary tool, etc.) such as the bit cutting edge portion 4 and the mounting portion 13. Thus, it may be formed only in the portion where the rotational torque is applied.
Further, since the hardened layer 2 is subjected to a plasma carburizing process capable of uniformly carburizing the surface S, the layer thickness is substantially constant and the hardness is substantially constant so as to be symmetrical with respect to the rotational axis L of the driver bit 1. It is formed uniformly. Therefore, even if the driver bit 1 rotates, the hardened layer 2 is not biased, and a local stress due to the eccentricity is not applied, so that a longer life can be realized.

The plasma carburizing treatment is a surface hardening in which carbon enters and diffuses from the material surface S of the object to be treated (driver bit 1) using carbon ions or radicals generated in a glow discharge plasma of a hydrocarbon-based process gas as a carbon source. Is the law.
This plasma carburizing treatment can form a thinner hardened layer 2 compared to conventional gas carburizing treatment and vacuum carburizing treatment, and has advantages such as less dimensional change and surface roughness change. Can be carburized, grain boundary oxidation does not occur, fatigue strength is improved, and the hardened layer 2 is difficult to peel off (that is, the bit material and carbon are firmly connected, and the surface S of the rotary tool bit 1 is Increases hardness and improves wear resistance).

Further, the plasma carburizing process is a clean process in consideration of the environment, such as soot that does not cause carburizing unevenness, so that the processing time is shortened and carbon dioxide is not discharged.
Further, in the plasma carburizing process, even if there are shielding parts such as holes and dents penetrating the workpiece, the carburization reaction wraps around the shielding member, and the hardened layer 2 is formed on the entire workpiece. Is possible.

In the present invention, the plasma carburizing process is performed by the rotating tool bit manufacturing apparatus 21 described below.
The rotary tool bit manufacturing apparatus 21 shown in FIG. 3 is a one-chamber plasma heat treatment furnace, and includes a chamber 22 capable of adjusting the internal pressure, a cooling gas supply unit 23 for feeding a cooling gas into the chamber 22, A process gas is supplied in the chamber 22 to the process gas supply unit 24, a rack 25 on which the driver bit 1 is placed in a process gas atmosphere in the chamber 22, and a cathode that applies a negative voltage to the driver bit 1 through the rack 25. 26 and an anode 27 (plasma source) that applies a positive voltage so as to generate plasma of a process gas around the driver bit 1 between the cathode 26 and a bias power source that generates a potential difference between the two electrodes 26 and 27 28 and a cooling fan 29 for circulating a cooling gas inside the chamber 22.

The rotating tool bit manufacturing apparatus 21 applies a negative voltage to the driver bit 1 and promotes the carburization reaction only when the process gas is turned into plasma, so that the hardening is achieved by controlling the voltage applied to the driver bit 1. The depth D (thickness) of the layer 2 can be reliably managed.
Next, a usage mode of the rotating tool bit (driver bit) manufacturing apparatus 21, that is, a manufacturing method of the rotating tool bit will be described.

First, a predetermined number of driver bits 1 are placed on the rack 25 in the chamber 22 in a standing state, in an upright state or in a suspended state.
After evacuating the chamber 22, a cleaning gas is sent from the gas supply unit (not shown) into the chamber 22, the cleaning gas is turned into plasma, and the surface S of the driver bit 1 is cleaned using ion bombardment in the plasma. To do.

After cleaning, the process gas introduced into the chamber 22 is turned into plasma by applying a voltage to the electrodes 26 and 27, and carbon ions and radicals generated in the plasma are permeated and diffused into the driver bit 1.
As a result, the hardened layer 2 is formed on the surface S of the driver bit 1, but the applied voltage is controlled to control the depth D of the hardened layer 2.

At this time, as described above, the hardened layer 2 is the desired layer so that the soft body 6 remains inside the hardened layer 2, particularly in the bit blade edge portion 4 so that the soft blade body 5 remains inside the hardened layer 2. The depth D is formed.
As a result, the adhesion between the carbon and the bit material is improved and the surface S hardness is increased to improve the wear resistance. At the same time, the internal soft body 6 can reduce the impact and suppress the generation of local stress (high Toughness) is realized.

In addition, since wear resistance and high toughness are performed in one process, the number of processes is reduced compared to the process of forming a twistable zone and the process of individualizing two materials, improving economy and simplifying work management. Can be planned.
4 and 5 show a driver bit 1 according to second and third embodiments of the present invention.
The driver bit 1 according to the second and third embodiments is a single driver bit having a bit end portion 11 only at one end.

A major feature of the driver bit 1 according to the second embodiment is that it has a hole 13a drilled in the direction of the rotation axis L from the base end side of the mounting portion 13.
By forming the hole 13a, the weight of the driver bit 1 can be reduced. By reducing the weight of the bit, it is possible to reduce a reaction force (a force proportional to the mass) that the bit blade edge portion 4 receives when it abuts on the screw groove when the bit rotates.

That is, the life of the driver bit 1 is increased by suppressing the rotational torque and impact applied to the driver bit 1.
Moreover, since the driver bit 1 of the second embodiment has the hardened layer 2 covering the whole, it is possible to exhibit sufficient shock absorption without providing the connecting portion 12 as a twistable band.
The driver bit 1 according to the third embodiment is a bit (diameter is about 4 mm) for tightening a small diameter screw having a screw diameter of 1 mm to 4 mm. That is, the bit end portion 11 is also thinner, and the blade portion of the bit blade edge portion 4 is formed smaller.

Thus, even if the bit cutting edge portion 4 is downsized or has a thin-walled portion, the hardened layer 2 is made to have a predetermined depth (as described above) by performing the above-described plasma carburizing treatment. 10 μm or more and 100 μm or less), the soft blade 5 can be left in the bit cutting edge 4.
Therefore, the impact can be alleviated by the bit cutting edge part 4 alone, the durability of the bit cutting edge part 4 is improved, and the life of the entire rotary tool bit 1 is extended.

In addition, by controlling the hardened layer 2 to a predetermined depth by plasma carburizing treatment, it is possible to cope with the shape change of the rotary tool bit 1 and the size, shape, etc. that can be formed of the hardened layer 2 increase (increase in variations) and are high. Versatility is realized.
In addition, this invention is not limited to embodiment mentioned above. Each configuration of the rotating tool bit 1 or the like, or the overall structure, shape, dimensions, and the like can be appropriately changed in accordance with the spirit of the present invention.

The rotary tool bit 1 is not limited to the driver bit, and may be any one having a tapered cutting edge such as a drill bit or a chuck bit as long as it can be attached to the rotary tool.
Moreover, the bit 1 for rotary tools does not need to be low carbon steel or high carbon steel, and may be a hardly carburized material such as titanium or SUS.
As described above, the hardened layer 2 does not have to be formed on the entire surface S of the rotating tool bit 1, and is provided only on the surface S of at least a portion where rotational torque is applied, such as the bit cutting edge portion 4 and the mounting portion 13. May be. For example, when the hardened layer 2 is provided only on the surface S of the bit cutting edge portion 4, the boundary edge between the hardened layer 2 provided and the uncured portion is perpendicular to the rotational axis L (the rotational axis). You may form circularly so that it may become symmetrical with respect to the center L).

1 Bit for rotating tool (driver bit)
2 Hardened layer 3 Soft core body 4 Bit cutting edge 5 Soft blade body S Surface of bit for rotary tool

Claims (5)

It is a bit for a rotating tool that has been subjected to carburizing treatment,
A rotating tool bit comprising: a hardened layer formed by subjecting the entire surface of the bit to plasma carburization; and a soft core positioned inside the hardened layer and having a hardness lower than that of the hardened layer. .   2. The bit for a rotary tool according to claim 1, wherein a soft blade body that is continuous with the soft core body inside the hardened layer and has a hardness lower than that of the hardened layer is left in the bit blade edge portion. It is a bit for a rotating tool that has been subjected to carburizing treatment,
At least the bit blade edge portion has a hardened layer formed by subjecting the surface to plasma carburizing treatment,
A bit for a rotary tool, characterized in that a soft blade that is located inside the hardened layer and has a hardness lower than that of the hardened layer is left in the bit cutting edge.   The bit for a rotary tool according to any one of claims 1 to 3, wherein a depth from the surface of the hardened layer is 10 µm or more and 100 µm or less.   A method of manufacturing a rotary tool bit, comprising: forming a hardened layer by performing plasma carburizing treatment on the entire surface of the rotary tool bit, and leaving a soft core having a lower hardness than the hardened layer inside the hardened layer.