WO2017208614A1

WO2017208614A1 - Electric tool

Info

Publication number: WO2017208614A1
Application number: PCT/JP2017/014060
Authority: WO
Inventors: 英樹松嶋; 陽介 ▲高▼崎
Original assignee: 株式会社マキタ
Priority date: 2016-06-01
Filing date: 2017-04-04
Publication date: 2017-12-07
Also published as: JP2017213659A

Abstract

Provided is an electric tool with a part that has a combination of multiple characteristics. A hammer drill (1), which is an example of the electric tool, is provided with a tool holder (8) comprising a front section (100) that is made of iron (including iron alloys) and a back section (102) that is made of aluminum (including aluminum alloys) and has a different melting point from the front section (100). The front section (100) and the back section (102) are joined by welding. The welding is laser welding. Moreover, the weld penetration depth, which is the depth to which the first metal portion penetrates into the second metal portion as a result of the welding, is 0.2 mm to 0.3 mm.

Description

Electric tool

The present invention relates to a power tool such as a hammer drill for performing a hammer operation on a workpiece.

As shown in Patent Document 1 below, a hammer drill having a tool holder that holds a hammer bit in a detachable manner at the front and transmits a rotation output of a motor to the hammer bit is known. A piston that reciprocates back and forth and a striker that slides inside the piston are arranged at the rear part of the tool holder, and the tool holder is integrated from the front part to the rear part.

JP 2013-13960 A

In the hammer drill, the tool holder is integrated. In order to ensure sufficient strength, the tool holder is made of iron (forged integrated structure) and is heavy.
Therefore, in order to reduce the weight, it can be considered that the tool holder is made of aluminum.
However, with aluminum, the strength of the tool holder, particularly the strength of the front hammer bit mounting portion, cannot be sufficiently ensured. If the hammer bit mounting portion is made of aluminum, there is a high possibility that the hammer bit mounting portion is deformed during the operation of the hammer bit and the subsequent operation of the hammer bit is hindered.
Therefore, a main object of the present invention is to provide a power tool including parts having a plurality of characteristics such as being lighter while having sufficient strength.

In order to achieve the above object, the invention according to claim 1 is provided with a component having a first metal portion and a second metal portion having a melting point different from that of the first metal portion. The first metal portion and the second metal portion are joined by welding.
The invention according to claim 2 is the above invention, wherein the welding is laser welding.
According to a third aspect of the present invention, in the above invention, the first metal portion is made of iron (including an iron alloy), and the second metal portion is made of aluminum (including an aluminum alloy). It is a feature.
According to a fourth aspect of the present invention, in the above invention, a penetration depth, which is a depth at which the first metal portion is melted into the second metal portion by the welding, is 0.2 mm or more and 0.3 mm or less. It is characterized by being.
According to a fifth aspect of the present invention, in the above invention, the first metal portion and the second metal portion are in contact with each other on at least two surfaces, and the welding is performed on at least two surfaces of the contact surfaces. Is to be enforced.
The invention according to claim 6 is characterized in that, in the above invention, the thickness of the portion where the welding is performed in the second metal portion is larger than the thickness of the portion where the welding is not performed.
According to a seventh aspect of the present invention, in the above invention, the first metal portion has a melting point higher than that of the second metal portion, and the first metal portion is a portion where the welding is performed. Is arranged outside the second metal portion.
According to an eighth aspect of the present invention, in the above invention, the length of the surface where the first metal portion and the second metal portion are in contact with each other at a site where the welding is performed is the length of the first metal portion. The length is more than twice the wall thickness.

According to the present invention, there is an effect that it is possible to provide an electric tool including parts having a plurality of characteristics.

It is a center longitudinal cross-sectional view of the hammer drill which concerns on the 1st form of this invention. FIG. 2 is a partially enlarged view of FIG. 1.

Hereinafter, embodiments of the present invention and modifications thereof will be described with reference to the drawings as appropriate.
The front, rear, top, bottom, left and right in the embodiment and the modification are determined for convenience of explanation, and may change depending on the status of work, the state of the moving member, and the like.
In addition, this invention is not limited to the following form and modification.

FIG. 1 is a central longitudinal sectional view of a hammer drill 1 which is an example of an electric tool (blow tool) according to the present invention, and FIG. 2 is an enlarged front view of FIG.
The hammer drill 1 includes a housing 2 that is a frame for holding various members, a power unit 4 that is disposed at the rear part of the housing 2 (the right part of the horizontally long FIG. 1) and generates power, and converts the power of the power unit 4 Intermediate portion 6 disposed in front of the power unit 4 for transmission, and disposed in front of the intermediate unit 6, and the power of the power unit 4 is transmitted through the intermediate unit 6 after appropriate conversion, A tool holder 8 is provided as a tip tool holding portion.

The power unit 4 includes a motor 10, and the housing 2 includes a cylindrical motor housing 12 in which the motor 10 is disposed.
A grip housing 18 formed by combining the left half and the right half is connected to the rear portion of the motor housing 12. The grip housing 18 can be gripped by an operator. A switch 20 is disposed in the grip housing 18. The switch 20 is connected to a trigger 22 that protrudes forward on the lower side of the motor housing 12. The switch 20 is switched according to whether or not the trigger 22 is pressed.
In addition, a cord 30 that can be connected to a power source is introduced into the grip housing 18.
The motor 10 and the cord 30 are connected to each other via the switch 20.
The motor 10 includes a motor shaft 32 that can rotate around the shaft, and is disposed in the motor housing 12 in a state where the direction of the motor shaft 32 is the front-rear direction. Teeth are formed at the front end of the motor shaft 32.

The intermediate portion 6 includes a drive conversion mechanism 40, a power transmission mechanism 42, a striking mechanism 44, and a gear housing 46 in which the left and right halves that form the outline of these are combined. The housing 2 includes a gear housing 46.

The drive conversion mechanism 40 is a mechanism for converting the rotational output of the motor shaft 32 into a reciprocating output in the front-rear direction. The drive conversion mechanism 40 is integrally attached to the intermediate shaft 50 in the front-rear direction and the rear end portion of the intermediate shaft 50. It includes a gear 52 that meshes with the teeth of the front end, a rotating body 54 that is integrally attached to the intermediate shaft 50, a swinging member 56 that is connected to the rotating body 54, and a piston 58 that is connected to the swinging member 56.
The rotating body 54 is a cylindrical member whose axial direction is the front-rear direction, and a guide 62 is formed on the outer surface thereof. Yes.
The swing member 56 extends vertically and is provided outside the rotating body 54 via a plurality of

balls

64, 64. As each rotating body 54 rotates, each ball 64 relatively follows the guide 62 and moves back and forth, thereby swinging the swinging member 56 back and forth.
The piston 58 is a bottomed cylindrical member having an axial direction in the front-rear direction and opened forward, and a link 66 connected to the upper end portion of the swinging member 56 is integrally provided at the bottom portion (rear end portion). ing. The piston 58 reciprocates in the front-rear direction via the link 66 as the swinging member 56 swings.

The power transmission mechanism 42 is a mechanism that transmits the rotational driving force transmitted to the intermediate shaft 50 of the drive conversion mechanism 40 to the tool holder 8, and includes a first gear 70 and a second gear 72.
The first gear 70 has a cylindrical shape, has a tooth portion on the outer surface of the front portion, and is fixed to the outer front portion of the intermediate shaft 50.
The second gear 72 has a ring shape and meshes with the teeth of the first gear 70 at the teeth formed on the outer surface.

The striking mechanism 44 is a mechanism for transmitting the output in the front-rear direction by the drive conversion mechanism 40 to the bit (tool, tip tool) mounted on the tool holder 8 as an impact force. It has a bolt 82.
The striker 80 is a cylindrical member whose axial direction is the front-rear direction, and has an outer diameter equivalent to the inner diameter of the piston 58 of the drive conversion mechanism 40, and is disposed so as to be slidable back and forth within the piston 58. Has been. A space surrounded by the rear surface of the striker 80 and the rear end portion of the inner surface of the piston 58 is an air chamber 84 that transmits the sliding motion of the piston 58 to the striker 80 by air pressure fluctuation.
The impact bolt 82 is a columnar member extending in the front-rear direction, and is disposed on the front side of the striker 80.

The tool holder 8 is a cylindrical member whose axial direction is the front-rear direction, and is provided with a cylinder portion 90 and a bit mounting portion 92 disposed in front thereof.
The cylinder part 90 has an inner diameter equivalent to the outer diameter of the piston 58, and the piston 58 is disposed in the cylinder part 90 so as to be movable back and forth. A second gear 72 of the power transmission mechanism 42 is fixed to the outside of the cylinder portion 90.
A bit is inserted into the bit mounting portion 92. On the rear side of the bit mounting portion 92, the front portion of the impact bolt 82 of the striking mechanism 44 is disposed. Chuck

balls

94 and 94 for fixing the bit are arranged on the bit mounting portion 92.

The tool holder 8 is formed by welding an iron front portion 100 (first metal portion) including a bit mounting portion 92 and an aluminum rear portion 102 (second metal portion) including a cylinder portion 90. Here, iron includes an iron alloy (for example, stainless steel), and aluminum includes an aluminum alloy (for example, duralumin, super duralumin, or ultra super duralumin). Iron and aluminum are different metals having different melting points.
At the rear end portion of the front portion 100, a diameter-expanded portion 110 whose inner diameter and outer diameter are expanded from the front side is disposed. On the other hand, a flange 112 is formed at the front end portion of the rear portion 102.
A cylindrical portion 114 in front of the flange 112 in the rear portion 102 is contained in the enlarged diameter portion 110 of the front portion 100, and the inner surface of the enlarged diameter portion 110 is in contact with the outer surface in front of the flange 112 (interface C). The rear surface of the diameter portion 110 is in contact with the front surface of the flange 112 (interface R).

Welding is performed between the enlarged diameter portion 110 (front welding portion) and the flange 112 or the cylindrical portion 114 (rear welding portion). Further, the thickness of the cylindrical portion 114 is larger than the thickness of other portions in the rear portion 102. In addition, the thickness of the enlarged diameter part 110 (front part welding enforcement site | part) may be made larger than the thickness of the other part in the front part 100. FIG.
Welding is performed by irradiating a laser (laser welding). The laser is emitted from a laser head of a laser output device (not shown). The welding may be electron beam welding performed by irradiating an electron beam.
Iron (front welding execution site) having a higher melting point than aluminum (rear welding execution site) is on the outside, and laser is first irradiated to the iron.

The laser is applied to each of four circumferences (four) around the axis of the tool holder 8. Here, the front-rear length of the contact portion between the front portion 100 and the rear portion 102 (front-rear length of the enlarged diameter portion 110, front-rear length of the cylindrical portion 114) is 12.0 mm (millimeter), and the rear surface of the enlarged diameter portion 110 (front surface of the flange 112) ) And a circumference that is 3.5 mm apart from the circumference. The front and rear length of the enlarged diameter portion 110 (the contact area between the front portion 100 and the rear portion 102) is reduced in size in order to ensure the welding quality by ensuring that the cooling time during welding is as short as possible and to ensure the welding strength. It is as long as possible (wide) as long as it does not hinder, and is preferably at least twice as long as the thickness of the enlarged diameter portion 110. The number of laser irradiation spots is not limited to four and may be three or less or five or more, and the arrangement of laser irradiation spots may be other than equal intervals. The order of laser irradiation may be any, for example, the laser may be sequentially irradiated from the circumference closest to the rear surface of the enlarged diameter portion 110 to the circumference adjacent to the front side, and vice versa. It may be present, or the center circumference may be irradiated first.
In each circumference, the laser irradiation is performed in such a manner that the tool holder 8 is fixed to the laser head in a state where the front part 100 and the rear part 102 of the tool holder 8 are combined (the cylindrical part 114 is put in the enlarged diameter part 110). This is done by being relatively rotated (moved) at the rotational speed. The laser head is arranged in a posture inclined (forward inclined) at a predetermined angle to the front side (upstream side) of the rotation direction of the tool holder 8 with respect to a straight line in the radial direction (radial direction) of the tool holder 8. Yes. For example, when the tool holder 8 is rotated clockwise as viewed from the front, and the laser head is disposed directly above the tool holder 8, the laser head is inclined to the right by a predetermined angle with respect to the vertical line. Be placed. At this time, the laser head tip is directly above, and the portion above the tip is on the right. By making the laser head tilt forward in this way, it is possible to prevent a situation in which smoke or the like generated during welding is applied to the laser, interrupting the laser and reducing the action of the laser. However, if it is tilted forward too much (when the forward tilt angle is too large), it becomes relatively difficult to arrange the laser head and to rotate relative to the tool holder 8 and to ensure the quality of welding. From such a viewpoint, the forward tilt angle (advance angle) is preferably 20 ° or more and 30 ° or less.

The action of the laser passes through the thickness of the enlarged diameter portion 110 (iron) and reaches the upper surface portion of the front portion (aluminum) of the flange 112 (see the dotted line in FIG. 2). It is adjusted so as to be melted at the penetration depth. The penetration depth can be adjusted by the laser output and the relative rotational speed according to the material (iron-aluminum) to be welded and the dimensions (thickness, etc.). The laser output is preferably set to 5 kW (kilowatt) or less from the viewpoint of making it easy to ensure appropriate bonding by preventing the amount of heat input from being too large. The relative rotational speed of the welded article and the laser head is set in accordance with the heat input amount and the welding efficiency, and is preferably 5 m / min (meters per minute) or less.
If the penetration depth is too shallow, the joint strength is too weak, and in the case of dissimilar metal welding, the joint strength is weakened even if it is too deep. The case of being too deep will be described below. When dissimilar metals are welded, several types of intermetallic compounds are produced depending on the temperature and the ratio of each metal (atomic ratio). In the case of an iron (Fe) -aluminum (Al) binary system, intermetallic compounds such as FeAl, Fe ₃ Al, FeAl ₂ , Fe ₂ Al ₅ , and FeAl ₃ can be generated. Many of such intermetallic compounds are formed brittlely in layers along the weld interface. In the Fe—Al binary system, the FeAl layer and the Fe ₃ Al layer have toughness and ductility, but other intermetallic compound layers are extremely brittle. And an intermetallic compound generate | occur | produces so much that there is much heat input, and heat input increases, so that the penetration depth is deepened. Thus, from the viewpoint of securing sufficient bonding strength while reducing the generation of intermetallic compounds, the penetration depth is preferably 0.2 mm or more and 0.3 mm or less. Currently, no dissimilar metal welding that can be controlled so as to generate only a kind of intermetallic compound (FeAl, Fe ₃ Al) that is not so brittle has been established.

The circumference close to the rear surface of the enlarged diameter portion 110 is welded also at the interface R between the rear surface of the enlarged diameter portion 110 and the front surface of the flange 112. Therefore, a predetermined distance from the interface R is set according to the heat capacity of the welded portion. Placed. By laser irradiation on this circumference, welding at the interface R (by residual heat) and welding at the interface C between the lower surface of the enlarged diameter portion 110 and the upper surface of the cylindrical portion 114 (by direct action) are ensured (two-surface welding). These interfaces C and R intersect (here, orthogonal).
The predetermined distance is preferably 400 μm or more and 600 μm or less from the viewpoint of securing sufficient bonding strength while reducing the formation of intermetallic compounds even in welding at the interface R between the rear surface of the enlarged diameter portion 110 and the front surface of the flange 112. It is.
The direction in which the interface R between the rear surface of the enlarged diameter portion 110 and the front surface of the flange 112 widens (radial direction) and the laser irradiation direction are the same direction (here, parallel). That is, the laser is irradiated so as to be adjacent to the interface R. Therefore, the heat of the laser is evenly applied to the interface, and uniform welding is ensured at the interface R.

An operation example of such a hammer drill 1 will be described.
When the operator pushes the trigger 22, the switch 20 is turned on, the motor 10 is activated, and the motor shaft 32 is rotated.
The rotation of the motor shaft 32 is transmitted to the intermediate shaft 50 via the gear 52.
The rotating body 54 of the intermediate shaft 50 reciprocates the piston 58 back and forth within the cylinder portion 90 of the tool holder 8 via the swing member 56. By the reciprocating motion of the piston 58, the air in the air chamber 84 acts as an elastic body, and the striker 80 reciprocates back and forth by the action. The striker 80 continuously collides with the impact bolt 82 by the reciprocating motion, and the impact force is transmitted to the bit attached to the tool holder 8 to generate a striking force in the front-rear direction. The hammer drill 1 performs an operation (hammer operation) of hitting a workpiece by the drive conversion mechanism 40 and the hitting mechanism 44 which are mechanisms that generate the hitting force.
On the other hand, the first gear 70 of the intermediate shaft 50 rotates the tool holder 8 around the central axis in the front-rear direction after the deceleration via the second gear 72 and rotates to the bit attached to the tool holder 8. Power is granted. The hammer drill 1 performs an operation (drilling operation) for processing a workpiece with a rotational force by a power transmission mechanism 42 that is a mechanism for generating the rotational force.

The tool holder 8 which is a component of the hammer drill 1 is formed by welding an iron front portion 100 and an aluminum rear portion 102, and can be reduced in weight compared to a case where all are made of iron, and the hammer drill 1 is reduced in weight. Can do. In particular, the tool holder 8 is disposed at the front part away from the center of gravity of the hammer drill 1, and vibration during operation is less likely to occur due to weight reduction, and it is possible to grip more stably.
Further, since the front portion 100 including the bit mounting portion 92 into which the rear portion of the bit enters is made of iron, it is possible to secure the strength required for the bit mounting portion 92, that is, the strength that can withstand the action received from the bit during processing. it can. On the other hand, even if the rear portion 102 including the cylinder portion 90 into which the piston 58 is inserted is made of aluminum, the strength required in the cylinder portion 90, that is, the strength required for guiding the forward and backward movement of the piston 58 is ensured.

The effect which the above hammer drill 1 can show | play is demonstrated.
In the hammer drill 1, a tool holder 8 having a metal front portion 100 and a metal rear portion 102 having a melting point different from that of the front portion 100 is provided, and the front portion 100 and the rear portion 102 are joined by welding. ing. Therefore, the parts are formed by a combination of different metals, and it is possible to provide the hammer drill 1 having parts having the characteristics (high strength, low weight, etc.) of each metal.
Moreover, since welding is laser welding, sufficient strength is ensured even when joining between dissimilar metals.
Furthermore, since the front part 100 is made of iron (including an iron alloy) and the rear part 102 is made of aluminum (including an aluminum alloy), the conventional iron parts can be reduced in weight while ensuring strength.
In addition, since the penetration depth, which is the depth at which the front portion 100 is melted with respect to the rear portion 102 by welding, is 0.2 mm or more and 0.3 mm or less, the joint portion becomes brittle while obtaining sufficient biting. Generation of intermetallic compounds is suppressed and the strength of dissimilar metal bonding is ensured.
Further, the front portion 100 and the rear portion 102 are in contact with each other on at least two surfaces (an interface C where the cylindrical surface of the enlarged diameter portion 110 and the cylindrical portion 114 are in contact, and an interface R where the rear surface of the enlarged diameter portion 110 and the front surface of the flange 112 are in contact). And welding is enforced in these 2 surfaces which contact. Therefore, the welding strength is further increased.
Furthermore, the thickness of the cylindrical portion 114 (rear welding portion) in the rear portion 112 is larger than the thickness of portions other than the cylindrical portion 114. Therefore, the mechanical strength of the welded portion is improved. In addition, heat generated during welding can be released more quickly, generation of intermetallic compounds can be suppressed, and sufficient strength can be ensured even in dissimilar metal joining.

In addition, this invention is not limited to the said form, For example, the following changes can be given suitably.
Other types of motors such as brushless motors may be used.
The configuration of the housing may be variously changed such that the motor housing and the grip portion are integrated, the motor housing and the cylinder housing are integrated, or the cylinder housing is further divided.
The number of contact surfaces and welding surfaces of the first metal part and the second metal part, or the number of intermediate shafts and gears is increased or decreased, the number of divisions of the metal part in the part is 3 or more, or the power cord is replaced. The battery connection portion is provided and the battery is driven, the mechanism relating to the drill operation is omitted, and only the mechanism relating to the hammer operation is arranged, or the first metal portion or the second metal portion is other The number of various parts can be adjusted by adjusting the penetration depth, distance from the interface, laser output, and the relative speed between the laser head and the welding target, depending on the characteristics of the formation of intermetallic compounds. Arrangement, presence / absence of installation, material, and the like may be changed as appropriate.

In addition, a part formed by combining different kinds of metals may be another part instead of the tool holder or together with the tool holder. Further, the present invention can be applied to other types of hammer drills, other electric tools, air-driven tools, cleaners, blowers, garden tools such as garden trimmers and high branch cutters, and the like.
For example, the piston and the link may be formed of different metals, and these may be welded.
Further, the spindle of the impact driver may be formed by welding two or more metal parts having different melting points.
Furthermore, the handle of the high branch cutting hook may be formed by welding of an iron portion and an aluminum portion or the like in order to ensure strength in reducing the weight. The handle of the high branch cutting hook is long, and in order to facilitate the work, it is required to reduce the weight while ensuring the strength. Currently, carbon fiber reinforced resin is widely used to meet such demands at a high level. Carbon fiber reinforced resin is expensive, and if composite metal parts are used instead of carbon fiber reinforced resin, It is possible to meet such a request at a lower cost.

Here, a part of invention concerning the manufacturing method of electric tool components is put together.
(1) combining a first metal part and a second metal part having a melting point different from that of the first metal part in a state where an interface exists;
Welding the interface,
A method of manufacturing a power tool part, comprising manufacturing a power tool part including the first metal part and the second metal part.
By this manufacturing method, a power tool component in which the first metal portion and the second metal portion are firmly coupled to each other is manufactured, and a power tool component having the characteristics of the first metal and the second metal is provided. .
(2) The method for manufacturing an electric power tool component according to (1), wherein the welding is laser welding.
By this manufacturing method, sufficient strength is ensured even when bonding between dissimilar metals.
(3) The electric motor according to (1) or (2), wherein the first metal is iron (including an iron alloy), and the second metal is aluminum (including an aluminum alloy). Manufacturing method of tool parts.
With this manufacturing method, a conventional iron part can be reduced in weight while ensuring strength.
(4) A penetration depth, which is a depth by which the first metal portion is melted into the second metal portion by the welding, is 0.2 mm or more and 0.3 mm or less (1) Thru | or the manufacturing method of the electric power tool components in any one of (3).
This manufacturing method suppresses the generation of an intermetallic compound that causes embrittlement of the joint while obtaining a sufficient joint strength, and ensures the strength of the dissimilar metal joint.
(5) There are two or more interfaces,
The method for manufacturing a power tool part according to any one of (1) to (4), wherein the welding is performed on at least two of the interfaces.
This manufacturing method further increases the welding strength.
(6) The electric motor according to any one of (1) to (5), wherein a thickness of the portion where the welding is performed in the second metal portion is larger than a thickness of the portion where the welding is not performed. Manufacturing method of tool parts.
By this manufacturing method, the mechanical strength of the welded portion is improved. In addition, heat generated during welding can be released more quickly, generation of intermetallic compounds can be suppressed, and sufficient strength can be ensured even in dissimilar metal joining.
(7) The laser is irradiated from a laser head,
Any one of (2) to (6), wherein the laser head is moved relative to the interface at the time of irradiation of the laser and is further inclined to the front side in the moving direction. The manufacturing method of the electric power tool components as described in 2.
By this manufacturing method, the situation where smoke during welding blocks the laser is prevented, and high-quality laser welding is provided.
(8) The method for manufacturing an electric power tool component according to any one of (2) to (7), wherein the output of the laser is 5 kilowatts or less.
By this manufacturing method, generation of brittle intermetallic compounds is suppressed, and sufficient welding strength is ensured.
(9) The two interfaces on which the welding is performed intersect each other,
The method of manufacturing a power tool part according to any one of (5) to (8), wherein the laser is irradiated so as to intersect one of the interfaces and to be adjacent to the other.
With this manufacturing method, two-surface welding is efficiently performed. Also, in welding at the interface adjacent to the laser (spreading in the same direction as the laser direction), by adjusting the adjacent distance, generation of brittle intermetallic compounds is suppressed, and sufficient strength is ensured. Become.

1 ·· Hammer drill, 8 ·· Tool holder (parts), 100 ·· Front part (first metal part), 102 ·· Rear part (second metal part), 110 ·· Expanded part (front welding performed) Part), 112 ·· flange (rear welding part), 114 · cylindrical part (rear welding part).

Claims

A component having a first metal part and a second metal part having a melting point different from that of the first metal part is provided;
The power tool, wherein the first metal portion and the second metal portion are joined by welding.
The power tool according to claim 1, wherein the welding is laser welding.
The first metal portion is made of iron (including an iron alloy), and the second metal portion is made of aluminum (including an aluminum alloy). Electric tool.
The penetration depth, which is the depth at which the first metal portion is melted into the second metal portion by the welding, is 0.2 mm or more and 0.3 mm or less. 4. The electric tool according to any one of 3.
The first metal portion and the second metal portion are in contact on at least two sides;
The power tool according to any one of claims 1 to 4, wherein the welding is performed on at least two of the contacting surfaces.
The power tool according to any one of claims 1 to 5, wherein a thickness of a portion where the welding is performed in the second metal portion is larger than a thickness of a portion where the welding is not performed.
The first metal portion has a higher melting point than the second metal portion;
The power tool according to any one of claims 1 to 6, wherein the first metal portion is disposed outside the second metal portion at a site where the welding is performed.
The length of the contact surface of the first metal part and the second metal part at the site where the welding is performed is at least twice the wall thickness of the first metal part. The power tool according to any one of claims 1 to 7, characterized in that: