[DESCRIPTION] [Invention Tit Ie]

A TAP OF PRODUCING SCREW [Technical Field]

<i> The present invention relates to a tap, which is a tool for forming internal threads using rotational motion, and, more particularly, to an improved thread forming tap, in which the structure of a shank part, which is coupled to a chuck and is rotated along with the chuck, is improved, thus preventing slippage from occurring between the chuck and the shank part. [Background Art]

<2> Generally, a thread forming tap is a tool that is coupled to a rotational machine, such as a tap chuck, a collet chuck or a drill chuck, and forms internal threads. Such a thread forming tap is widely used in an industrial (metal) field.

<3> The typical structure of such a tap is described. As shown in FIGS. 1 and 2, the tap includes a shank part 3 and a thread forming part 2.

<4> The shank part 3 has a cylindrical sectional shape, or a rectangular end, is coupled to a rotational machine, for example, a tap chuck, a collet chuck or a drill chuck, and functions to receive rotational force. The thread forming part 2 functions to form internal threads in various kinds of metal using the rotational force.

<5> In the typical tap, the most important part is the shank part 3, which is coupled to the chuck, as well as the thread forming part 2 for performing a forming process.

<6> The reason for this is because, if a play, that is, slippage, occurs between the chuck and the shank part 3 in the state in which the shank part 3 is coupled to the chuck when an inexpensive drill chuck is used, the internal threads may not be accurately formed, and the tap and the chuck may be damaged.

<7> Accordingly, in order to prevent slippage between the shank part of the tap and the chuck, a worker must firmly maintain the coupling between the

shank part of the tap and the chuck by applying a large force through a chuck handle, or must firmly maintain the coupling between the shank part of the tap and the chuck by welding and fastening a separate auxiliary handle to the chuck handle and applying a larger force thereto.

<8> However, when maintaining the coupling between the shank part of the tap and the chuck, as described above, problems occur in that the gear of the chuck is worn away by the excessive force, and in that the chuck handle becomes bent .

<9> Conventionally, in order to solve these problems, an expensive tap chuck is used, a keyless chuck, which exerts a strong tightening force as the number of rotations increases, is used, or a collet chuck, which has precise concentricity, is used. However, there is a problem in that the cost can be increased because the tap chuck, the keyless chuck and the collet chuck are very expensive products.

<io> Furthermore, various sizes of collet chucks and tap chucks must be provided, which also increases the cost thereof.

<ii> Furthermore, in the case in which coupling with the collet chuck is made and a rectangular tap, or a hexagonal tap, which is filed on the same day, has a hexagonal sectional shape, a problem occurs in that interference between the spring depression of the collet chuck and the edge portions of the tap, which has an angled sectional shape, occurs, and thus they are not compatible with each other. [Disclosure] [Technical Problem]

<12> Accordingly, the present invention has been made keeping in mind the above problems occurring in the prior art, and an object of the present invention is to provide a thread forming tap, in which the shank part of the tap is formed to have a rounded triangular sectional shape, so that no slippage occurs during rotation even when it is coupled with a typical chuck, thus enabling internal threads to be accurately formed, and in which a typical chuck, instead of a tap chuck, a keyless chuck or a collet chuck,

which is expensive, can be used, thus reducing the cost.

<13> Another object of the present invention is to provide a thread forming tap, which, when used with a collet chuck, does not interfere with the spring depression of the collet chuck, thus being compatible therewith. [Technical Solution]

<i4> In order to accomplish the above objects, the present invention provides a thread forming tap, including: a blade part including a thread forming part for forming internal threads; and a shank part integrally formed with one end of the blade part, coupled with a chuck to receive rotational force, and configured such that three round parts and three linear parts are alternately formed in a predetermined range in a direction from one end of the shank part, which is coupled to the chuck, to the blade part, thus having a rounded triangular sectional shape.

<15> Furthermore, the present invention further includes a slippage preventing surface that is formed on a surface of the linear part of the shank part through a knurling process. [Description of Drawings]

<16> FIG. 1 is a perspective view of a typical thread forming tap;

<17> FIG. 2 is a sectional view of FIG. 1;

<18> FIG. 3 is a perspective view of a thread forming tap according to the present invention;

<19> FIG. 4 is a plan view of FIG. 3; and

<20> FIG. 5 is a perspective view showing another embodiment of the present invention.

<2i> description of reference numerals of principal elements>

<22> 1; (screw forming) tap

<23> 2; blade part

<24> 3; shank part

<25> 4; linear parts

<26> 5; round parts

<27> 6; slippage preventing surface

[Mode for Invention]

<28> The above and other objects, features and advantages of the present invention will be more clearly understood to those skilled in the art from the detailed description of the present invention, taken in conjunction with the accompanying drawings and provided below.

<29> FIG. 3 is a perspective view of a thread forming tap according to the present invention, FIG. 4 is a plan view, and FIG. 5 is a perspective view showing another embodiment of the present invention.

<30> As shown in the drawings, the thread forming tap 1 includes a blade part 2 and a shank part 3.

<3i> The blade part 2 is a part that actually forms internal threads in various kinds of metal. For this purpose, a thread forming part is formed on the surface of the blade part 2.

<32> The shank part 3 is integrally formed with the blade part 2, is coupled to a chuck, and functions to receive rotational force, thus allowing the thread forming part of the blade part to form internal threads.

<33> In this case, the shank part 3 is a characteristic part of the present invention, and is configured such that three round parts 5 and three linear parts 4 are alternately formed in a predetermined range in a direction from one end of the shank part 3 to the blade part on the basis of a portion that is coupled to the chuck. Consequently, the overall shank part has a polygonal sectional shape, or, more precisely, a rounded triangular sectional shape.

<34> Meanwhile, although the shank part 3, as described above, is formed to have a rounded triangular sectional shape due to the round parts 5 and the linear parts 4 so as to prevent slippage from occurring when coupled with a typical chuck, it is more preferable for a slippage preventing surface 6 to be formed on the outer surface of the shank part 3, that is, on the surface of the linear portion 4 through a knurling process in order to multiply the effect.

<35> In the thread forming tap according to the present invention, which is

constructed as described above, in the case where the shank part 3, having a rounded triangular sectional shape, is coupled to an inexpensive typical chuck using the round parts 5 and the linear parts 4, no slippage occurs between the shank part and the chuck at high rotation.

<36> In addition, when coupling with the collet chuck is made, interference with the spring depression of the collet chuck is eliminated by the forming of the round parts, so that the thread forming tap can be easily coupled and used. That is, the thread forming tap is compatible with the collet chuck.

<37> Accordingly, internal threads can be precisely and accurately formed on kinds of metal using the thread forming part of the blade part 2.

<38> Although the present invention has been shown and described above in conjunction with a specific embodiment, those skilled in the art will easily appreciate that various modifications and variations are possible within the range that does not depart from the spirit and scope of the invention as disclosed in the accompanying claims. [Industrial Applicability]

<39> As described above, in the thread forming tap according to the present invention, the shank part, which is coupled with the chuck, has a rounded triangular sectional shape due to the round parts and the linear parts, which are alternately formed, so that no slippage occurs between the shank part and the chuck.

<40> Accordingly, no slippage occurs between the shank part and the chuck at high rotation even when a typical chuck, which is inexpensive, is used, so that internal threads can be accurately formed on kinds of metal without the use of the tap chuck, the keyless chuck, and the collet chuck, which are expensive, and, in addition, the cost can be reduced.

<4i> Furthermore, the use of the tap chuck, which is expensive and is inconvenient to detachably attach, can be eliminated, easy detachable attachment and increased accuracy can be achieved even when an inexpensive typical chuck is used, and compatibility is improved because no interference with the spring depression occurs when coupling with the collet chuck is

performed.

<42> Furthermore, an effect in which a step is formed between the shank part and the forming part due to the linear part is acquired, so that forward movement in the traveling direction of the forming part is interrupted when a forming process is performed, therefore damage to the tool can be prevented.