JPH10146721A - Threading tap - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a shank of a threading tap from being slid by a machining reactive force when a drill chuck is used in making a hole for a female thread and in cutting a female thread. SOLUTION: On the outer periphery of the shank 1 gripped by a drill chuck of a machine tool are formed three planes 4 which constitute three surfaces of a regular triangular prism whose central axis agrees with the central axis of the shank 1. The planes 4 are made to such an extent that a cylindrical surface 7 forming the outer periphery of the shank 1 before chamfering is left between adjacent planes 4. Since the plane 4 is tangent to the outer peripheral surface of the shank 1, when a large cutting reactive force is applied to a threading tap, the threading tap is slightly slid and the claws of the drill chuck bite into the plane 4. Therefore, after there happens a slight slide, the threading tap is not slid even if a larger cutting reactive force is applied to the threading tap.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thread tap used for machining a female screw on an inner peripheral surface of a pilot hole mounted on a drill chuck for a machine tool such as a drilling machine and drilled with a drill or the like.

[0002]

2. Description of the Related Art A thread tap is widely used as a cutting tool for machining a female screw for tightening a bolt, and is generally mounted on a drilling machine in many cases. An ordinary drill chuck mounted on an ordinary drilling machine has a structure in which a shank of a threading tap inserted into the chuck is gripped by three-way claws. The three claws are opened and closed using the wedge action of the conical surface, and a large gripping force is obtained by the boost action of the wedge.

[0003] Conventionally, there has been known a threaded tap having a square cross section as shown in FIG. 4 in which a tip portion of a shank is chamfered from four sides to fit the threaded tap on a tap handle. As a holder for holding a tap of this kind, a dedicated holder is provided which presses a set screw from a side to a portion having a rectangular cross section to prevent slippage between a drill chuck and a shank.

[0004]

The gripping force of the drill chuck does not have enough gripping force to withstand the reaction force acting on the threading tap at the time of threading. In other words, three claws grip the shank of the tap,
In a cutting tool such as a tap, whose shank is thinner than the tap diameter, the contact surface thereof is not sufficiently large, and slip occurs due to the reaction force of the thread cutting process. In general, taps up to M6 are machined with a drill chuck, and those larger than that are machined by attaching a tap holder dedicated to the tap to the spindle of the drilling machine. Most of the ordinary thread cutting and preparation of the prepared hole are processed up to M16, but it is troublesome to replace the drill chuck and the tap holder one by one when processing the female screw of M6 or more. .

Accordingly, the present invention completely eliminates slippage of a threading tap due to a reaction force when a drill chuck is used in the preparation of a prepared hole of a female screw up to about M16 and the thread cutting, which are often performed by a drilling machine. It is an object of the present invention to provide technical means that can prevent such problems.

[0006]

According to a first aspect of the present invention, there is provided a thread tap having a regular triangular prism having a central axis aligned with the central axis of the shank on the outer periphery of a portion of the shank which is gripped by a drill chuck of a machine tool. It is characterized by having three planes 4 forming planes.

According to a second aspect of the present invention, in the threading tap according to the first aspect, the flat surface 4 is formed with a depth that leaves a cylindrical surface 7 that forms the outer periphery of the shank before chamfering between the adjacent flat surface. It is characterized by having.

According to a third aspect of the present invention, in the threaded tap according to the first or second aspect, the diameter of the shank 1 is smaller than the outer diameter of the tap 2.

[0009]

The thread tap according to the present invention is mounted by gripping the flat surface 4 with three claws of a drill chuck. Since the flat surface 4 is tangential to the outer peripheral surface of the shank 1, it slightly slides when a large cutting reaction force acts on the threading tap. However, the slip causes the claws of the drill chuck to bite into the flat surface 4. Such a slip occurs only slightly, and after such a slip occurs, even if a larger cutting reaction force acts on the threading tap,
No shank slippage occurs.

The plane 4 does not need to be provided too deeply.
If it is too deep, it is not preferable because the cross-sectional area of the shank is reduced and the strength is reduced. The plane 4 is
Since the rotation axis can be machined with a cylindrical grindstone parallel to the axis of the tap, even a tap having a step 3 at the root of the shank can form the plane 4 up to the root of the shank, Accordingly, the drill chuck can be inserted into the shank 1 until the step 3 comes into contact with the tip of the drill chuck.

[0011]

1 and 2 show an embodiment in which a shank 1 is a threaded tap having a smaller diameter than a tap 2. FIG. The structure of the tap 2 portion is a conventionally well-known structure, and can be various structures such as a straight tap, a spiral tap, and a point tap. Shank 1 is tap 2
A step 3 is formed between the tap side and the base of the shank 1 with a smaller diameter.

As shown in FIG. 2, the shank 1 has three flat surfaces 4 whose outer peripheral surfaces are chamfered by grinding in three directions. These planes 4 are three planes of a regular triangular prism whose central axis coincides with the central axis 5 of the shank.

FIG. 3 shows an embodiment of a threading tap having a shank diameter equal to the tap diameter. A portion of the shank 1 to be inserted into the rotary tool holder has a regular triangular prism similar to that shown in FIG. Three planes 4 are formed.

[Brief description of the drawings]

FIG. 1 is a perspective view of a first embodiment.

FIG. 2 shows a cross section of a shank.

FIG. 3 is a perspective view of a second embodiment.

FIG. 4 is a perspective view of a conventional shank tip.

[Explanation of symbols]

 1 shank 4 flat surface 7 outer peripheral surface

Claims (3)

[Claims] 1. Three planes each forming a surface of a regular triangular prism having a central axis coinciding with the central axis of the shank on the outer periphery of a shank (1) gripped by a drill chuck for a machine tool.
(4) A threading tap characterized by the following. 2. The thread tap according to claim 1, wherein the plane (4) is formed with a depth that leaves a cylindrical surface (7) that forms the outer periphery of the shank before flattening between adjacent planes. 3. The thread tap according to claim 1, wherein the diameter of the shank is smaller than the outer diameter of the tap.