JPH0499804A - Manufacture of jaws of clamping tool - Google Patents

Abstract

PURPOSE:To easily manufacture highly accurte and high hardness jaws even in the case of having complicate shape by adding an organic binder to an iron based powder, executing debinder after compacting, sintering and heat treatment. CONSTITUTION:The organic binder containing wax conductor as an essential material is added to the iron based powder such as SKH57 powder, and the powder is compacted to a prescribed shape by injection-compacting, degreasing and sintering, and further, by executing the heat treatment of quenching and tempering, etc., to adjust the hardness thereby obtaining the jaws of clamping tool for fastening and fixing a drill-bit, driver-bit, etc.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Operational Application) The present invention relates to a method of manufacturing a jaw used in a chuck for tightening and fixing a drill bit, driver pin, etc.

(Prior art) The claws used in tightening tools are required to have rigidity that can withstand the torque caused by rotation and sudden stops, while the precision of machine tools and tools has increased as technology has become more sophisticated and complex in recent years. Coupled with the demand for improvements, shapes are becoming more complex and the precision required for parts is becoming increasingly strict.

Conventionally, this type of claw was manufactured by cutting a metal material, followed by heat treatment, and then finishing to maintain accuracy, but the complexity of the cutting process led to high costs.

Therefore, in the case of chuck jaws for machine tools, which require high precision but are also expensive, it was possible to use the conventional means described above, but electric For tool chucks, it has been difficult to meet this requirement in terms of cost.

For this reason, the chuck jaws of power tools, which have stricter cost requirements than machine tools, are mainly manufactured by forging.
Generally, costs were reduced due to the mass production effect.

However, when manufacturing claws by forging, it has not been possible to use high-hardness materials, such as high-speed steel or die steel, due to the durability of the mold. On the other hand, the quality required for a chuck is to grip hard drill bits and driver bits.
High hardness is required to grip this firmly to prevent it from slipping. However, due to material limitations, claws manufactured by forging
It is not possible to achieve high hardness, and even if the required hardness were achieved, the toughness would be impaired and there was a risk of cracking or chipping during use.

Furthermore, in terms of accuracy, it cannot be achieved by forging alone, so when it is made into a chuck, the center runout is large. It was not possible to do so, and it was necessary to add a radius, and the drill bit was not particularly easy to bite into, causing slippage.

In order to solve the above problems, for example,
No. 9009 proposes a technique in which iron-based powder is molded and then sintered to obtain a tightening claw.

(Problems to be Solved by the Invention) However, in this conventional example, no heat treatment was performed after sintering, and the hardness and rigidity required for the nail could not be satisfied. Also, even if heat treatment is performed,
Since the sintering process was performed in a mixed gas atmosphere of argon and hydrogen, surface decarburization occurred and the problem was that it could not be hard enough to bite into a drill bit.

In addition, regarding the method for removing the organic binder, the above-mentioned conventional example (
JP-A No. 62-99009) does not mention the details. Generally, organic binders are mainly composed of wax or thermoplastic resin, and when heat is applied, a softening phenomenon occurs before decomposition.

If this softened organic binder is subsequently removed by decomposition and vaporization, the softened organic binder will remain in the molded product, causing deformation and sag in some corners, making it difficult to maintain dimensional accuracy. Become.

As a result, there were problems such as center runout of the drill bit when it was assembled as a chuck.

This invention was made to solve the above problem, and its purpose is to provide a tightening tool that can easily produce highly accurate and highly hard nails even in complex shapes. The purpose of the present invention is to provide a method for manufacturing nails.

(Means for Solving the Problems) In order to achieve the above-mentioned object, the method of the present invention includes a method for manufacturing a claw for a tightening tool for tightening and fixing a drill bit, a driver bit, etc. After adding a binder and forming into a predetermined shape, the organic binder is removed and sintered.
Further, the method is characterized in that the hardness is adjusted by heat treatment, and the step of removing the organic binder is a method of removing the organic binder by heating, and the method includes heating at a pressure lower than atmospheric pressure, and further reducing the pressure. The temperature is changed depending on either the temperature monitored during the process or the variation in the amount of at least one type of gas generated.

(Function) According to the above structure, in the method of the present invention, an organic binder mainly consisting of wax or the like is added to iron-based powder such as 5KH57 powder in order to impart fluidity, and the iron-based powder such as 5KH57 powder is molded into a predetermined shape as a nail by means such as injection molding. After forming into the shape, dewaxing and sintering are performed, and the sintered crystals are further subjected to heat treatment such as quenching and tempering to finally adjust the hardness.

In the above, degreasing is performed by a method of removing the organic binder by heating, and controlling the volume of gas generated by heating under a pressure lower than atmospheric pressure to suppress rapid expansion of decomposed gas, At this time, by changing the degree of pressure reduction according to fluctuations in the furnace temperature and the amount of gas generated, it is possible to control the volume of gas generated to be approximately constant and prevent cracking or blistering of the molded product.

(Example) Preferred embodiments of the present invention will be described below.

The characteristic feature of the present invention is that in the method of manufacturing the claws for tightening and fixing trilby bits, driver bits, etc., after adding an organic binder to iron-based powder and molding it into a predetermined shape. , the organic binder was removed and sintered, and the hardness was further adjusted by heat treatment.

In this example, 5KH57 powder manufactured by the water atomization method was used as the raw material powder, and as shown in FIG. 5, the cumulative 50% diameter was about 12 μm.

In order to impart fluidity to this powder, an organic binder mainly consisting of wax and thermoplastic resin was added, and the powder was kneaded under heat using a pressure kneader. The blending ratio of this powder to the binder was 54:46 by volume.

The material kneaded in this manner is molded into a predetermined shape as a claw by injection molding. In this case, since the fired crystal undergoes linear shrinkage of 18.6% relative to the molded product, it is necessary to design the mold in anticipation of this shrinkage.

Next, the organic binder is removed from the nail formed by the above method by heating.

Further, in the present invention, the step of removing the organic binder is a method of removing the organic binder by heating, and the heating is performed under a pressure lower than atmospheric pressure, and the degree of pressure reduction is further monitored during the step. It is characterized in that the change is made in accordance with either the temperature generated or the amount of at least one type of gas generated.

Thus, in the exemplary embodiment, during removal of the organic binder, the molded article is heated in a furnace having the system shown in FIG. This system includes a furnace body 1, a vacuum evacuation system 2, and a decomposition gas detection section 3, and this decomposition gas detection section 3 has a configuration as shown in Fig. It is now possible to detect gas components that cause the gas to change, and change the degree of vacuum depending on the degree of the gas component.

The operation is shown in Figure 3 (a) (b) and Figure 4 (a) (b).
The explanation will be based on. In this example, carbon monoxide was used as the gas to be detected. In this case, since the organic binder does not decompose at the beginning of heating, -carbon oxide is not detected.

When the temperature starts to rise, the organic binder, especially the wax component, melts.
It begins to soften, but does not decompose - no carbon oxide is detected. Therefore, during this time, there is no vaporization due to decomposition, so by creating a high vacuum, capillary action is promoted, the organic binder in the molten state is removed, and deformation of the molded product can be prevented. Upon further heating, the organic binder begins to decompose and -carbon oxides begin to be detected. In this state, the organic binder is removed from the liquid state and decomposed into the gas phase state of vaporization.

In this case, if the degree of vacuum is kept constant, Figures 3(a) and 4
As shown in Figure (a), the partial pressure and gas volume of specific components of the decomposed gas increase dramatically, resulting in
), it is necessary to lower the degree of vacuum and reduce the partial pressure and gas volume of specific components of the generated cracked gas. That is, at a constant temperature, the gas has the equation of state PV=co
From nst, pressure and volume are inversely proportional. Therefore, from the point at which the organic binder begins to decompose and vaporize, it is necessary to reduce the degree of vacuum according to the degree of decomposition and to control the volume of decomposed gas generated. Otherwise, the molded product may crack or blister due to the rapidly expanded decomposition gas.

After removing the organic binder by the above-mentioned means, sintering is performed by heating under vacuum. At this time, the temperature was raised to 1235°C over 7 hours and maintained for 1 hour.

Further, the degree of vacuum was on the order of 10-'torr. This sintered crystal is quenched at 1180°C and tempered twice at 580°C to complete a product as shown in Figure 6. The density of this finished product exceeded 99%, the surface hardness was 11IC63 or more, and the bending strength was 300''/cm, □ or more, and had sufficient properties as a nail.

Next, an example of a chuck using the claws obtained in this example will be explained based on FIG. 7.

Each of the plurality of claws 4 for tightening the drill bit has an inclined outer surface and has an L-shaped engagement piece 5 at the rear end, and this retaining piece 5 is used as a claw support means. It is engaged with a retaining groove 7 provided in a float screw 6 as a. Furthermore, the winter melon 4 is housed in a slit 9 formed in a conical guide 8, and wing pieces 10 are provided on the conical surface of the outer surface of the guide.
is engaged. The float screw 6 is screwed into a female thread at the top of the shaft 11, which has a knurled bottom.
Furthermore, after being housed in a tapered bush 12 having a tapered inner surface, it is fixed with a lock handle 13.

After further incorporating the ratchet 14, the plastic handle 15 and cap 16 are combined to complete the chuck.

As described above, when the handle 13 is rotated, the shaft 1
1 rotates, but at this time the float screw 6 is connected to the shaft 11.
It moves in the axial direction because it is prevented from rotating. When this movement is directed forward, the pawls 4 move in the axial direction along the taper of the inner surface of the tapered bush 12, and at the same time gather to the center to fix the drill bit.

At this time, if the accuracy of the pawl is sufficient as shown in Figure 8 (a), center runout will not occur, but if the accuracy of the pawl is insufficient as shown in Figure 8 (b), it will move in the axial direction. When doing so, the jaws are not evenly centered, and the drill bit 17 is not gripped at the center of rotation, resulting in center runout.

(Effects of the Invention) As explained above, this invention is a method for manufacturing a tool claw for tightening and fixing drill bits, driver bits, etc., by adding an organic binder to iron-based powder and forming it into a predetermined shape. After molding, the organic binder is removed and sintered, and the hardness is adjusted by heat treatment, and the step of removing the organic binder is a method of removing the organic binder by heating, The cutting process is performed by heating at a pressure lower than atmospheric pressure, and by changing the degree of pressure reduction depending on either the temperature monitored during the process or the variation in the amount of at least one type of gas generated. It is possible to easily produce complex-shaped claws with the hardness, strength, and precision required for fasteners without the need for machining.

[Brief explanation of the drawing]

Figure 1 is a diagram showing an overview of the organic binder removal device, Figure 2 is a diagram showing details of the decomposed gas detection section, and Figure 3 (a) is a diagram showing the state of the gas in the furnace when the degree of vacuum is constant. , FIG. 3(b) is a diagram showing the state of the gas in the furnace when the degree of vacuum is controlled, FIG. 4(a) is a diagram showing the state of change in the volume of generated gas when the degree of vacuum is constant, FIG. (b) is a diagram showing the change in the volume of generated gas when controlling the degree of vacuum, Figure 5 is a diagram showing the fineness distribution of the 5KH51 powder used in this example, and Figure 6 is a diagram showing the state of change in the volume of generated gas when the degree of vacuum is controlled. Figure 7 is an exploded view of the tool used for tightening using claws, and Figure 8 (a) shows the external appearance of the claws obtained in the example.
FIG. 2 is a diagram showing the state of vibration of the bit due to the accuracy of the claw. 1... Furnace body 2... Vacuum exhaust system 3... Decomposition gas detection section 4... Claw

Claims (2)

[Claims] (1) In a method for manufacturing clamping claws for tightening and fixing drill bits, driver bits, etc., an organic binder is added to iron-based powder, formed into a predetermined shape, and then the organic binder is removed and sintered. A method for manufacturing a fastener claw, which further comprises adjusting the hardness through heat treatment. (2) In the nail manufacturing method according to claim 1, the step of removing the organic binder is a method of removing the organic binder by heating, and heating is performed under a pressure lower than atmospheric pressure.
Furthermore, the method for manufacturing a claw of a fastening tool is characterized in that the degree of pressure reduction is changed depending on either a temperature monitored during the process or a variation in the amount of at least one type of gas generated.