JP2014083614A - Processing method of screw hole - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a burr of a size of exceeding an allowable value and a burr of an easily separable form from being generated in a chamfering part formed in an opening part on the cut-through side of a prepared hole, when a threading tap cuts through a through-prepared hole.SOLUTION: When forming a female screw by using the threading tap for the prepared hole 2 penetratingly formed in a machinable material 1, the chamfering part 3 chamfered in advance in two stages, is formed on the peripheral edge on the cut-through side of the tap of the prepared hole 2, and a chamfering angle α2 of a second chamfering part 3of its chamfering part is set to α2>(θ/2) to an angle θ of a thread of a processed screw, and the threading tap is cut into the prepared hole 2 having its chamfering part 3, and its tap is cut through a surface of the second chamfering part.

Description

  The present invention relates to a method for machining a screw hole in which a female thread is formed on the inner peripheral surface of a through hole using a threaded tap (hereinafter also simply referred to as a tap). The present invention relates to a method for processing a screw hole that enables a female screw to be processed without the use of a screw.

  When a structural material is fastened using screws or bolts, it is necessary to process a screw hole in the fastening partner material. The screw hole is formed by using a method in which a pilot hole is provided in advance in a fastening partner material by drilling or the like and a female screw is cut with a tap on the inner peripheral surface of the pilot hole.

  When the lower hole at this time is a through hole, burrs are generated on the peripheral edge of the hole when the tap passes through the lower hole.

  When the burrs are not allowed to remain because they are large or easily peeled off, the generated burrs are generally removed using a deburring tool. A deburring process is required in addition to the thread cutting process, resulting in a decrease in productivity.

  Therefore, as a countermeasure, a special tap and a tap holder shown in Patent Document 1 below have been proposed. The tap described in Patent Document 1 is a tap for deburring and is provided with a tapered deburring portion at the rear (the side with the shank) of the effective thread portion that forms the female screw.

  With the tap, the internal thread is processed into the through hole, and the finished tap is fed to the position where the deburring part moves to the tap exit side of the lower hole, and the spring is biased in the radial direction from that position. By reversing the direction and pulling back the tap, the generated burr is removed at the deburring portion of the tap.

JP-A-8-90341

  When the tap proposed in Patent Document 1 is used, burrs generated on the peripheral edge of the hole on the cut-off side of the tap can be removed by a tap that is extracted from the hole. A tap provided with a section is required, and a general-purpose tap cannot be used.

  Also, the tap holder must be able to urge the held tap in the radial direction, and a general-purpose tap holder cannot be used.

  For this reason, a method of removing burrs generated on the peripheral edge of the through-bore hole on the tap cut-off side by using a deburring tool is frequently used.

  This invention prevents a burr having a size exceeding the allowable value or a burr having an easily peelable shape from occurring in a chamfered portion formed in an opening on the cutout side of the lower hole when the tap cuts through the through hole. It is an issue.

  In order to solve the above-described problems, in the present invention, a threaded hole machining method for forming a female screw using a threaded tap in a prepared hole penetrating a work material, wherein the prepared hole tap is A chamfered portion that is chamfered in two stages in advance is formed on the periphery of the cut-out side.

  Then, the chamfering angle α2 of the second chamfered portion of the chamfered portion is set to α2> (θ / 2) with respect to the thread angle θ of the thread to be processed, and the chamfered portion chamfered in two steps is provided. A screw hole is machined by a method in which a threaded tap is cut into the lower hole and the tap is cut through the surface of the second chamfered portion.

  The second chamfered portion has an outer diameter larger than the diameter of the valley of the female thread processed by the threading tap. For this purpose, the threading tap passes through the surface of the second chamfered portion.

  In addition, the said 2nd chamfering part points out the chamfering part arrange | positioned rather than the 1st chamfering part on the tap entry side of a lower hole by making the tap cut-out side of a lower hole into a 1st chamfering part. Moreover, the said chamfering angle means the angle made with the surface orthogonal to the axial center of the screw hole processed.

  The chamfer angle α1 of the first chamfered portion on the tap cut-out side of the lower hole with respect to the second chamfered portion satisfies the condition of α1 ≧ θ / 2.

  The chamfering angle α1 of the first chamfered portion is preferably 30 °, and the chamfered angle α2 of the second chamfered portion is preferably about 40 ° to 60 °.

  For example, as a screw hole provided in a part or structural material manufactured by powder metallurgy, a method of forming a lower hole and chamfering a peripheral edge by molding with a press die is usually employed. The chamfering angle in this method is set to 30 ° so that the tip of the chamfered portion molding portion of the press mold does not become an acute angle.

  On the other hand, the internal thread to be machined by a tap is generally a triangular screw having a thread angle of 60 °, and burrs are particularly likely to occur when the triangular screw is cut into a chamfered hole with a chamfering angle of 30 °. . Therefore, the present invention can be expected to have a particularly remarkable effect when it is used for threading when a threaded hole of a triangular screw is provided in a sintered product that is often required to be chamfered at a chamfering angle of 30 ° around the periphery of the threaded hole.

  If the chamfering angle α2 of the second chamfered portion is too small, the burr suppressing effect is thin. Conversely, if the chamfered angle α2 is too large, the processing area of the second chamfered portion is unnecessarily increased. Is appropriate.

  A land having a small width perpendicular to the axis of the lower hole may be interposed between the second chamfered portion and the first chamfered portion.

  The pilot hole may be a drilled hole. In that case, if a drill with a chamfering blade for machining the first and second double-sided chamfers at the end of the effective blade length is used as a drill for preparing a lower hole, the first and second chamfered parts are lowered. Can be processed simultaneously with the hole.

  According to the screw hole processing method of the present invention, the chamfered portion which is changed in two steps of the chamfering angle obtained by combining the first chamfered portion and the second chamfered portion that are originally required to be formed at the periphery of the screw hole. A threaded hole is machined by a method in which a threaded tap is cut into a prepared hole having a chamfered portion and the tap is cut through the surface of the second chamfered portion.

  The second chamfered portion has an angle difference with the slope of the screw thread larger than that of the first chamfered portion, and the tap cuts through the surface of the second chamfered portion. It is not possible to create burrs that are unacceptable in size or form. Therefore, it is possible to eliminate the burr removal step without using a specially shaped tap or a special tap holder.

Sectional drawing which shows an example of the pilot hole formed in the work material Sectional drawing which shows the other example of the pilot hole formed in the work material Sectional drawing which shows an example of the relationship between the 2nd chamfer and the thread processed into a pilot hole Image when tap thread cuts through second chamfer

  DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of a screw hole machining method according to the present invention will be described below with reference to FIGS.

  An example of a chamfered portion formed in advance in a prepared hole provided in the work material is shown in FIGS. The work material 1 in FIG. 1 is a sintered plate formed by powder metallurgy. The work material (sintered plate) 1 is provided with a prepared hole 2 formed by a mold. A chamfered portion 3 that is molded simultaneously with the lower hole 2 is provided at the opening edge on one end side of the lower hole 2.

The chamfered portion 3 is a combination of the first chamfered portion _3-1 and the second chamfered portion _3-2 having different chamfer angles (the chamfer angles are set in two stages), and the opening of the lower hole 2. the first chamfer angle α1 of chamfer 3 _-1 30 ° located section, the chamfer angle α2 of the second chamfered portion _3-2 located on the tap enters side of the lower hole 2 than the first chamfer 3 _-1 Each is set to 40 °.

Chamfer angle α1 of the first chamfered portion 3 _-1 is set to 30 ° in order to protect the mold for forming the first chamfered portion 3 _-1. For the same reason, the first chamfer 3 _-1 between the second chamfer 3 _-2, land 4 of perpendicular small width and the lower hole 2 axis is interposed.

When the second chamfer 3 _-2 molded core with the lower hole, by forming the land molding surface in the mold for molding the first chamfer 3 _-1, forming the first chamfered portion 3 _-1 Although it is possible to prevent the tip of the punch die from becoming too sharp, the land 4 is only a preferable element when the work material is a sintered product.

The first chamfered portion 3 _-1 second chamfer 3 _-2, as shown in FIG. 2, may be connected directly. 2 is a drilled hole. In this case as well, the first chamfered portion _3-1 and the second chamfered portion 2 are formed in the opening portion of the lower hole 2 on the tap cut-off side. chamfer 3 of which is a combination of chamfer _3-2 bunk chamfer angle setting is provided.

A chamfer angle [alpha] 1 of the first chamfered portion _{3 -1} of the chamfer 3 chamfer angle [alpha] 2 of the second chamfer _{3 -2,} 1 Like [alpha] 1 = 30 °, an [alpha] 2 = 40 °.

  In the present invention, such a chamfered portion 3 is provided in advance in the opening portion of the lower hole 2, and a threaded tap 5 is cut into the lower hole 2 to process the screw hole as shown in FIG.

1, the chamfered portion 3 of the lower hole formed in the workpiece 1 in FIG. 2, the chamfer angle α1 of the first chamfered portion 3 _-1 is 30 °. On the other hand, the threading tap 5 is a tap for cutting a triangular screw having a thread angle of 60 °. Since the threading tap 5 in this situation the weather on the surface of the first chamfer 3 _-1, the slope angle of the slope and the surface of the first chamfer 3 _-1 mountains off the tap screws are identical, threading tap 5 Thin foil-like burrs that can be easily peeled off can be formed at the locations where the cracks pass through.

In order to avoid the problem, the second chamfered portion _3-2 has a female thread valley diameter (= diameter of the complete thread portion of the tap) in which the outer diameter d _< b> ₂ of the second chamfered portion 3-2 is processed by a threaded tap. greater than d1, so that survive the threading tap 5 on the surface of the second chamfered section _3-2.

In the second chamfered portion _3-2 , the chamfer angle α ₂ is set to 40 °, which is larger than ½ (30 °) of the thread angle θ of the thread to be processed. Thus, for survived the plane of the second chamfered portion _3-2 of the tap, as shown in FIG. 4, (the same inclination angle and the slope 6 of the valley of the internal thread which is processed) slopes thread taps This is done in a crossed state, and the entire area of the slope of the thread is kept parallel to the surface of the chamfered portion, so that it can be prevented from being cut through at the same time, and the occurrence of burrs on the cut-out side is suppressed.

  The description here is given by taking as an example a case where the condition of the chamfering angle of the chamfered portion provided at the opening edge on the tap cut-off side of the lower hole being 30 ° is satisfied as an example. However, when a chamfered portion having a chamfering angle of 45 ° is provided in the opening on the tap cut-off side of the lower hole, for example, when a screw hole having a slope angle of 45 ° is machined using a special tap, the second is used. When the chamfering angle of the chamfered portion is set to 45 ° or more (preferably about 55 °), burr suppression can be expected.

  A 6 mm thick sintered plate {composition: Fe-2 wt% Cu-0.8 wt% C (ISO material standard F-08C2)} provided with a lower hole in FIG. 1 and a two-step chamfered portion by molding. The screw hole was processed using a general-purpose triangular screw tap.

  Lower hole diameter d: φ5 mm, first chamfered portion chamfered angle α1: 30 °, second chamfered portion chamfered angle α2: 40 °, second chamfered portion outer diameter d2: φ6.04 mm, screw hole diameter d1: When the screw hole is machined with specifications of φ6.00mm, the chamfered portion without the second chamfered portion is provided, and the burr generated on the cut-off side of the tap by the conventional method in which the tap is cut through the chamfered portion is not generated. The burr removal process is no longer necessary.

DESCRIPTION OF SYMBOLS 1 Work material 2 Pilot hole 3 Chamfering part 3 _-1 1st chamfering part _3-2 2nd chamfering part 4 Land 5 Thread cutting tap 6 The slope of the valley of the internal thread processed

Claims (3)

A threaded hole machining method for forming a female screw using a threaded tap in a lower hole (2) formed through a work material (1), wherein the peripheral edge on the side where the tap of the lower hole (2) is cut through The chamfered portion (3) chamfered in two stages in advance is formed, and the chamfering angle α2 of the second chamfered portion ( _3-2 ) of the chamfered portion is set to α2> with respect to the thread angle θ of the thread to be processed. (theta / 2) is set to, not cut the threading tap down hole (2) having a chamfered chamfer _(3-2) on the two stages, the the threading tap second chamfer (3 _{- 2} ) A screw hole machining method, wherein the screw hole is machined by a method of cutting through the surface. A chamfered portion (3) in which the chamfering angle α1 of the first chamfered portion (3 _-1 ) on the tap cut-out side of the lower hole ( ₂ ) than the second chamfered portion (3 _-2 ) is set to θ / 2. The screw hole machining method according to claim 1, wherein the screw hole is machined by a lower hole (2) having a threading tap. The chamfering angle α1 of the first chamfered portion (3 ₋₁ ) is set to 30 °, the chamfered angle α2 of the second chamfered portion ( _3-2 ) is set to 40 °, and a screw hole of a triangular screw is formed using a threading tap. The processing method of the screw hole of Claim 1 or 2 which processes.

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