Measuring Tool and Measuring Method for Measuring Female Screw Position

Abstract

Provided are a measuring tool and a measuring method capable of improving the measurement accuracy of the axial center position of a female screw. Since the pitch p of the external thread 12 in the shaft portion 11 of the measuring tool 10 is different from the pitch P of the female screw 31 in a specific standard, when the shaft portion 11 is fitted to the female screw 31 while rotating the measuring tool 10, the flanks 13 and 33 of the external thread 12 and the female screw 31 come into contact with each other at two positions separated in the axial direction, and the rotation of the measuring tool 10 stops. As a result, in a method of measuring the axial center C2 position of the female screw 31 by applying a stylus 40 to the plug portion 15 of the measuring tool 10 fitted to the female screw 31, the measurement accuracy can be improved.

Description

Technical Field

[0001] The present invention relates to a measuring tool and a measuring method capable of improving the measurement accuracy of the axial center position of a female screw.

Background Art

[0002] Conventionally, in order to measure the axial center position of a female screw formed on a workpiece, a measuring tool as disclosed in Patent Document 1 is used. The measuring tool of Patent Document 1 includes a shaft portion including a male screw that is fitted into the female screw, and a columnar plug portion that is arranged coaxially with the shaft portion. A tapered surface that tapers toward the male screw is formed over the entire circumference at the edge on the male screw side inside the plug portion.

[0003] In the measurement in Patent Document 1, first, the male screw of the measuring tool is fitted (screwed) into the female screw until the tapered surface of the measuring tool abuts against the tapered chamfered surface formed at the entrance of the female screw. Next, a stylus (probe) or calipers of a three-dimensional measuring instrument is applied to the outer peripheral surface of the plug portion of the measuring tool, and the position of the axial center of the measuring tool is measured (calculated) from the position of the outer peripheral surface and the radius of the plug portion. The position of the axial center of this measuring tool is regarded as the axial center position of the female screw.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, in Patent Document 1, even if the axis of the measuring tool is likely to coincide with the axis of the chamfered portion due to the contact between the chamfered portion and the tapered surface, the chamfered portion and the internal thread are not necessarily coaxial. Therefore, in Patent Document 1, there is a possibility that the axis of the measuring tool does not coincide with the axis position of the internal thread, and there is a possibility that the axis position of the internal thread cannot be accurately measured. Further, if the work surface on which the internal thread is formed is not perpendicular to the axis of the internal thread, the chamfered portion and the tapered surface cannot be sufficiently brought into contact. In this case, it is difficult for the axis of the measuring tool to coincide with the axis of the internal thread, and there is a possibility that the axis position of the internal thread cannot be accurately measured.

[0006] The present invention has been made to solve the above-described problems, and an object thereof is to provide a measuring tool and a measuring method capable of improving the measurement accuracy of the axis position of an internal thread.

Means for Solving the Problems

[0007] In order to achieve this object, the measuring tool of the present invention is for measuring the axis position of an internal thread formed in accordance with a specific standard, and includes a shaft portion formed on an outer peripheral surface of a male thread that is fitted into the internal thread, and a columnar plug portion that is arranged coaxially with the shaft portion and connected to the shaft portion. The flank angle of the male thread in the shaft portion is the same as the flank angle of the internal thread in the specific standard, and the pitch of the male thread in the shaft portion is different from the pitch of the internal thread in the specific standard.

Effects of the Invention

[0008] According to the measuring tool described in claim 1, since the pitch of the male thread in the shaft portion is different from the pitch of the female thread in a specific standard, when fitting the male thread into the female thread while rotating the measuring tool, the flanks of the male thread and the female thread come into contact with each other at two positions separated in the axial direction, and the rotation of the measuring tool stops. Further, since the flank angles of both the male thread and the female thread are the same, the contact between the flanks is a surface contact, and it is difficult for the female thread and the measuring tool to loosen and they are easily coaxially aligned. As a result, in the method of measuring the axial center position of the female thread by applying a stylus or calipers to the plug portion of the measuring tool fitted into the female thread, the measurement accuracy can be improved.

[0009] According to the measuring tool described in claim 2, in addition to the effect achieved by the measuring tool described in claim 1, the following effect is achieved. Let the flank angle of the male thread and the female thread be represented by θ. Let the minimum value of the effective diameter of the female thread in a specific standard be D2min, the tolerance of the effective diameter of the female thread be TD2, and the pitch of the female thread be represented by P. Let the effective diameter of the male thread in the shaft portion be d2 and the pitch of the male thread be represented by p. When the formula "(TD2 + |D2min - d2|) / (|P - p|·tan2θ) ≤ 4" using these values is satisfied, within 4 rotations after starting to fit the male thread of the measuring tool into the female thread, the flanks of the male thread and the female thread come into contact with each other at two positions separated in the axial direction, and the rotation of the measuring tool stops. Thereby, the working efficiency of attaching the measuring tool to the female thread can be improved.

[0010] According to the measuring tool described in claim 3, in addition to the effect achieved by the measuring tool described in claim 1, the following effect is achieved. Let the flank angle of the male thread and the female thread be represented by θ. Let the minimum value of the effective diameter of the female thread in a specific standard be D2min and the pitch of the female thread be represented by P. Let the effective diameter of the male thread in the shaft portion be d2 and the pitch of the male thread be represented by p. When the formula "|D2min - d2| / (|P - p|·tan2θ) ≥ 2" using these values is satisfied, more than 2 pitches of the male thread are fitted into the female thread before the rotation of the measuring tool stops. Thereby, the looseness of the measuring tool with respect to the female thread can be further suppressed, and the measurement accuracy of the axial center position of the female thread can be further improved.

[0011] According to the measuring tool described in claim 4, in addition to the effects achieved by the measuring tool described in claim 1, the following effects are achieved. Since the effective diameter of the male thread in the shaft portion is smaller than the minimum value of the effective diameter of the female thread in a specific standard, it is easier to fit the male thread into the female thread.

[0012] According to the measuring tool described in claim 5, in addition to the effects achieved by the measuring tool described in claim 1, the following effects are achieved. Since the effective diameter of the male thread in the shaft portion is equal to or greater than the minimum value of the inner diameter of the female thread in a specific standard, the contact area between the flanks of the male thread and the female thread can be ensured. As a result, play between the female thread and the measuring tool can be further suppressed, and their coaxiality (the amount of deviation of the axis) can be easily reduced, so that the measurement accuracy of the axial position of the female thread can be further improved.

[0013] According to the measuring tool described in claim 6, in addition to the effects achieved by the measuring tool described in claim 2, the following effects are achieved. The axial length of the male thread in the shaft portion is 4 times or more the pitch of the male thread. As a result, under the condition of "(TD2 + |D2min - d2|) / (|P - p|·tan2θ) ≤ 4", the male thread can be fitted into the female thread until the flanks of the male thread and the female thread come into contact at two axially separated positions and the rotation of the measuring tool stops. As a result, play between the female thread and the measuring tool can be more easily suppressed, and they can be more easily made coaxial, so that the measurement accuracy of the axial position of the female thread can be further improved.

[0014] The measuring method described in claim 7 is a method for measuring the axial position of a female thread using the measuring tool described in any one of claims 1 to 6, and achieves the same effects as any one of claims 1 to 6.

[0015] Note that the measuring tool may be configured by combining any two or more of claims 2 to 6. Also, the method for measuring the axial position of the female thread may be a method of measuring using a measuring tool that combines any two or more of claims 2 to 6.

Brief Description of the Drawings

[0016]

Figure 1

Figure 2

Figure 3

Mode for Carrying Out the Invention

[0017] Hereinafter, preferred embodiments will be described with reference to the accompanying drawings. FIG. 1 is a front view of a measuring tool 10 in one embodiment. For convenience in this specification, the upper side and the lower side of each drawing will be described as the upper side and the lower side of the measuring tool 10, respectively.

[0018] The measuring tool 10 is an auxiliary tool used for measuring the axial center position of a female screw 31 (see FIG. 2) provided on a workpiece 30 (see FIG. 2), and is formed of metal, synthetic resin, or the like. The measuring tool 10 is a shaft-shaped member having a shaft portion 11, a plug portion 15, and a handle portion 17 on the same axial center C1, and these respective portions are integrally formed. The upper end of the shaft portion 11 is connected to the lower end of the plug portion 15, and the upper end of the plug portion 15 is connected to the lower end of the handle portion 17.

[0019] Note that the axial center C1 of the shaft portion 11, the axial center C1 of the plug portion 15, and the axial center C1 of the handle portion 17 may be slightly different due to manufacturing errors or the like. The amount of deviation of these axial centers C1 is referred to as coaxiality. The coaxiality between the shaft portion 11 and the plug portion 15 is preferably 0.010 mm or less.

[0020] The shaft portion 11 is a portion constituting one end portion of the shaft-shaped member. A plurality of screw threads are continuously formed in the axial direction on the outer peripheral surface of the shaft portion 11 to form a male screw 12. The male screw 12 is provided from a position axially away from the plug portion 15 to the vicinity of the lower end of the shaft portion 11. In the male screw 12, the surface connecting the peak and the valley of the thread is a flank 13.

[0021] The plug portion 15 is a part that constitutes the middle portion of the shaft-like member. The plug portion 15 is formed in a columnar shape having an axis C1, and the radius R from the axis C1 to the outer peripheral surface of the plug portion 15 is configured to be substantially constant in the axial direction and the circumferential direction. On the outer peripheral surface of the plug portion 15, when measuring the axial position of the female thread 31, a stylus 40 (see FIG. 2) of a three-dimensional measuring instrument, calipers, etc. are applied.

[0022] The handle portion 17 is a part that constitutes the other end portion of the shaft-like member. When the measuring tool 10 is rotated to fit (screw in) the shaft portion 11 into the female thread 31, the handle portion 17 is grasped by the finger of the measurer and a rotational force is applied.

[0023] The handle portion 17 is formed in a substantially columnar shape having an axis C1. A part of the outer peripheral surface of the handle portion 17 is cut out so as to be a flat surface 18 substantially parallel to the axis C1. A plurality of grooves 19 are formed in a lattice pattern on the outer peripheral surface of the handle portion 17 other than the flat surface 18. By these flat surface 18 and the plurality of grooves 19, the grip force between the finger of the measurer and the handle portion 17 can be ensured, and the measuring tool 10 can be easily rotated. Note that at least one of these flat surface 18 and grooves 19 may be omitted, and a known configuration for ensuring the grip force may be applied to the handle portion 17.

[0024] The outer diameter 2R (twice the radius R) of the plug portion 15 is larger than the outer diameter d of the male thread 12 of the shaft portion 11 and the outer diameter of the handle portion 17, respectively. Thereby, it is easy for the measurer or the like to distinguish the shaft portion 11, the plug portion 15, and the handle portion 17 from the appearance. Further, since the outer peripheral surface of the plug portion 15 protrudes radially with respect to the shaft portion 11 and the handle portion 17, it is easy to apply the stylus 40 or the like to the outer peripheral surface of the plug portion 15.

[0025] The constricted portion between the male thread 12 and the plug portion 15 has a reduced diameter with respect to them. Thereby, when the male thread 12 is formed by cutting or the like, it can be suppressed that the processing affects the plug portion 15 or the processing tool interferes with the plug portion 15.

[0026] Next, referring to FIGS. 2 and 3, the female screw 31 into which the male screw 12 (shaft portion 11) is fitted will be described. FIG. 2 is a schematic diagram showing a state where the measuring tool 10 is fitted to the female screw 31 of the work 30. FIG. 3 is a schematic diagram of the measuring tool 10 and the work 30 showing an enlarged view of the III portion of FIG. 2. FIGS. 2 and 3 show a schematic cut end face view of the work 30 in a cut plane including the axis C2 of the female screw 31, and a schematic front view of the measuring tool 10. Further, in FIG. 3, the illustration of the hatching showing the cut plane of the work 30 is omitted.

[0027] The female screw 31 is a screw formed on the inner peripheral surface of the hole, and one or more are provided in the work 30 made of metal, synthetic resin, or the like. The female screw 31 may penetrate the work 30 or may be non-penetrating. In the female screw 31, the surface connecting the peak and the valley of the thread is the flank 33.

[0028] The female screw 31 is formed in accordance with a specific standard. Examples of the specific standard include those defined by ISO (International Organization for Standardization), JIS (Japanese Industrial Standards), ANSI (American National Standards Institute), etc. However, the specific standard is not limited to these exemplified standards, and may be a standard individually defined by each organization or each operator. Further, the male screw 12 of the measuring tool 10 is formed so as to be fitted into the female screw 31, and a part of the male screw 12 may be formed in accordance with a specific standard.

[0029] For example, the standards for general-purpose metric screws shown in JIS B0205-1:2001 (ISO 68-1:1998), JIS B0205-2:2001 (ISO 261:1998), JIS B0205-3:2001 (ISO 262:1998), JIS B0205-4:2001 (ISO 724:1993), and JIS B0209-1:2001 (ISO 965-1:1998) etc. are referred to as standard S. Hereinafter, the present invention will be described using this standard S as a specific standard, but a standard other than standard S may also be used as a specific standard.

[0030] According to this standard S, the flank angle θ of the external thread 31 is 30 degrees. The flank angle θ of the internal thread 12 is made the same as the flank angle θ of the external thread 31 for any specific standard. This sameness means that the difference between the flank angles θ of the external thread 31 and the internal thread 12 is within the tolerance of the flank angle θ.

[0031] Note that the flank angle θ of the external thread 31 is the angle formed between a straight line perpendicular to the axis C2 and the flank 33 in the cross-section including the axis C2. The flank angle θ of the internal thread 12 is the angle formed between a straight line perpendicular to the axis C1 and the flank 13 in the cross-section including the axis C1.

[0032] Furthermore, according to the standard S, for example, as excerpted in Table 1 below, for the nominal diameter which is the reference dimension of the root diameter D of the external thread 31, the pitch P of the external thread 31, the maximum value D2max of the effective diameter D2 of the external thread 31, the minimum value D2min of the effective diameter D2, the maximum value D1max of the internal diameter D1 of the external thread 31, the minimum value D1min of the internal diameter D1, etc. are determined.

Table 1

[0033] Note that, for example, the nominal diameter M6 means that the reference dimension of the root diameter D of the external thread 31 is 6 mm. Also, the effective diameter D2 of the external thread 31 is the diameter of a virtual cylinder where the width of the thread groove is equal to the width of the thread crest. Similarly, the effective diameter d2 of the internal thread 12 is the diameter of a virtual cylinder where the width of the thread groove is equal to the width of the thread crest.

[0034] The internal thread 12 of the measuring tool 10 to be fitted to the external thread 31 of such a standard S should be one that can be fitted to the external thread 31 (having an equivalent nominal diameter), and it is sufficient that the pitch p of the internal thread 12 is different from the pitch P of the external thread 31. That is, the effective diameter d2, the outer diameter d, etc. of the internal thread 12 may be different from the standard S or may conform to the standard S. For example, for an external thread 31 with a nominal diameter of M10 and a pitch P of 1.5 mm, the internal thread 12 may conform to the standard S with a nominal diameter of M10 and a pitch p of 1.25 mm.

[0035] In addition, when the pitch P of the female thread 31 of the standard S and the pitch p of the male thread 12 of the measuring tool 10 are different, it is preferable that the absolute value of their difference is 0.01 times or more of the pitch P, that is, |P - p| ≧ 0.01P. However, when 0.01P is less than 0.01 mm, it is said that |P - p| ≧ 0.01 mm means that the pitch P of the standard S and the pitch p of the measuring tool 10 are different. In these cases, it can be said that the pitch P of the standard S and the pitch p of the measuring tool 10 are different by more than the tolerance of the general pitches P and p.

[0036] Hereinafter, a method for measuring the position of the axis C2 of the female thread 31 using such a measuring tool 10 will be described. First, in the preparation process, the measuring tool 10 (male thread 12) as described above corresponding to the female thread 31 of the standard S to be measured is prepared.

[0037] Next, in the attachment process, while the measurer rotates the prepared measuring tool 10, the male thread 12 is fitted to the female thread 31 to be measured. At this initial stage, due to the difference in the pitches P and p, only one of the upper surface side or the lower surface side of the flank 13 of the male thread 12 partially contacts the flank 33 of the female thread 31, so the measurer hardly feels the rotational resistance.

[0038] If the measuring tool 10 is continuously rotated in this state, for example, at the position A shown in FIG. 2, the lower surface side of the flank 13 of the male thread 12 contacts the upper surface side of the flank 33 of the female thread 31, and at the position B shown in FIG. 2, the upper surface side of the flank 13 of the male thread 12 contacts the lower surface side of the flank 33 of the female thread 31. As a result, the rotational resistance suddenly increases, and the measurer is made to stop rotating the measuring tool 10.

[0039] When this rotation stops, the flanks 13 and 33 of the male thread 12 and the female thread 31 are in contact with each other at two positions separated in the axial direction. Further, since the flank angles θ of both the male thread 12 and the female thread 31 are the same, the contact between the flanks 13 and 33 becomes surface contact. As a result, it is difficult for the female thread 31 and the measuring tool 10 to loosen, and the axis C2 of the female thread 31 and the axis C1 of the measuring tool 10 (shaft portion 11, male thread 12) are likely to be coaxial.

[0040] In the measurement process after such an attachment process, as shown in Fig. 2, by moving the stylus 40 of the three-dimensional measuring instrument and applying it to the outer peripheral surface of the plug portion 15, the contact position is determined. In the measurement process, further, the position of the axis C1 of the measuring tool 10 is measured (calculated) from this contact position and the radius R of the plug portion 15, and the position of the axis C1 is set as the position of the axis C2 of the female screw 31.

[0041] The position of the axis C2 measured in this way may be used as the position of the female screw 31. Further, for example, when the workpiece 30 is formed in a shaft shape and the female screw 31 is formed on the axial end surface of the workpiece 30, the coaxiality between the measured position of the axis C2 and the axis of the workpiece 30 may be measured. Further, for example, the perpendicularity of the female screw 31 with respect to the surface of the workpiece 30 on which the female screw 31 is formed may be measured from the measured position of the axis C2.

[0042] Note that the measurement of the position of the axis C2 of the female screw 31 is not limited to the method using the stylus 40 of the three-dimensional measuring instrument. For example, the measuring tool 10 is respectively fitted to two female screws 31 provided on the workpiece 30, and calipers are applied to the outer peripheral surfaces of the plug portions 15 of the two measuring tools 10, so that the position of the axis C2 of the female screw 31 may be measured as the interval between the two female screws 31. Further, the position of the axis C2 of the female screw 31 may be measured by applying the laser light emitted from the laser distance meter to the outer peripheral surface of the plug portion 15.

[0043] In any measurement method, by using a through-side screw plug gauge (GP) instead of the measuring tool 10, the position of the axis C2 of the female screw 31 can be easily measured. However, in this case, there is a possibility that the position of the axis C2 of the female screw 31 cannot be accurately measured due to play during fitting or inclination when the end face of the plug portion of the gauge is applied to the surface of the workpiece 30 on which the female screw 31 is formed. Further, if a step gauge (one in which a plurality of effective diameters are set in a stepped manner) is used instead of the through-side screw plug gauge, play can be suppressed, but it is necessary to try whether each of the many step gauges can be fitted to the female screw 31 one by one, and there is a problem in terms of cost in preparing them.

[0044] On the other hand, in the case of measurement using the measuring tool 10, as described above, the female screw 31 and the measuring tool 10 are less likely to rattle and are easily coaxially aligned, so the measurement accuracy of the position of the axis C2 of the female screw 31 can be improved. Furthermore, since only one measuring tool 10 is required unlike a step gauge, the cost of the measuring tool 10 can be easily reduced.

[0045] Since the measuring tool 10 is provided with the handle portion 17, it is difficult to allow the measurer to hold the plug portion 15. As a result, it is difficult for oil or dust of the measurer's finger to adhere to the outer peripheral surface of the plug portion 15. As a result, it is possible to suppress a decrease in the measurement accuracy of the position of the axis C2 of the female screw 31 due to oil, dust, etc. on the outer peripheral surface of the plug portion 15.

[0046] Also, in the measurement using the measuring tool 10, strictly speaking, since the position of the axis C1 of the plug portion 15 is measured from the contact position of the stylus 40, even if the axis C2 of the female screw 31 and the axis C1 of the shaft portion 11 substantially coincide, there is a possibility that the measurement result of the position of the axis C2 of the female screw 31 may deviate by the amount of the coaxiality between the shaft portion 11 and the plug portion 15. Therefore, as described above, if the coaxiality between the shaft portion 11 and the plug portion 15 is 0.010 mm or less, the measurement accuracy of the position of the axis C2 of the female screw 31 can be ensured.

[0047] In the fitting in the mounting process, when the effective diameter D2 of the female screw 31 is the maximum value D2max, the number of rotations Tmax from the start of rotation of the measuring tool 10 until the rotation stops is as shown in the following formula 1. Formula 1: Tmax = |D2max - d2| / (|P - p| · tan2θ)

[0048] Note that using the tolerance TD2 = D2max - D2min of the effective diameter D2 of the female screw 31, Formula 1 can be rewritten as shown in the following Formula 2. Formula 2: Tmax = (TD2 + |D2min - d2|) / (|P - p| · tan2θ)

[0049] It is preferable that this Tmax satisfies Tmax ≤ 4, that is, satisfies "(TD2 + |D2min - d2|) / (|P - p|·tan2θ) ≤ 4". If this is satisfied, within 4 rotations after starting to fit the shaft portion 11 into the female thread 31 of the standard S, the flanks 13 and 33 of the male thread 12 and the female thread 31 come into contact at two axially separated positions and the rotation of the measuring tool 10 stops. Thereby, the working efficiency of attaching the measuring tool 10 to the female thread 31 can be improved.

[0050] Furthermore, it is more preferable that Tmax ≤ 3.5, and even more preferably Tmax ≤ 3. In these cases, the working efficiency of attaching the measuring tool 10 to the female thread 31 can be further improved.

[0051] When Tmax satisfies Tmax ≤ 4, the axial length L (see FIG. 1) of the male thread 12 of the shaft portion 11 is preferably 4 times or more the pitch p of the male thread 12. Furthermore, the axial length of the female thread 31 is also preferably 4 times or more the pitch p of the male thread 12. In these cases, under the condition that Tmax ≤ 4, the shaft portion 11 can be fitted into the female thread 31 until the flanks 13 and 33 come into contact at two axially separated positions and the rotation of the measuring tool 10 stops. That is, it is possible to suppress the shaft portion 11 from passing through the through-type female thread 31 without the rotation of the measuring tool 10 stopping, or the shaft portion 11 hitting the bottom of the non-through-type female thread 31 and the rotation of the measuring tool 10 stopping. As a result, it becomes easier to further suppress the play between the female thread 31 and the measuring tool 10 and to make them more coaxial, so that the measurement accuracy of the position of the axis C2 of the female thread 31 can be further improved.

[0052] Similarly, when Tmax satisfies Tmax ≤ 3.5, the length L of the male thread 12 and the axial length of the female thread 31 are preferably 3.5 times or more the pitch p, and when Tmax satisfies Tmax ≤ 3, the length L of the male thread 12 and the axial length of the female thread 31 are preferably 3 times or more the pitch p.

[0053] The shaft portion 11 has a constricted portion between the male thread 12 and the plug portion 15, and the outer diameter of the constricted portion is smaller than the root diameter d3 of the male thread 12. Therefore, even if the entire male thread 12 is fitted into the female thread 31, it is possible to prevent the constricted portion of the shaft portion 11 from interfering with the female thread 31 or the plug portion 15 from contacting the surface of the workpiece 30. Since it is possible to prevent the axis C1 of the shaft portion 11 from tilting with respect to the axis C2 of the female thread 31 due to this interference or contact, the measurement accuracy of the position of the axis C2 of the female thread 31 can be further improved.

[0054] Further, when the effective diameter D2 of the female thread 31 is the minimum value D2min, the number of rotations Tmin from the start of rotation of the measuring tool 10 until the rotation stops is as shown in Equation 3 below. Equation 3: Tmin = |D2min - d2| / (|P - p| · tan2θ)

[0055] It is preferable that this Tmin satisfies 2 or more, that is, satisfies "|D2min - d2| / (|P - p| · tan2θ) ≥ 2". If this is satisfied, the male thread 12 of 2 pitches p or more can be fitted to the female thread 31 of the standard S. As a result, the play of the measuring tool 10 with respect to the female thread 31 can be further suppressed, and the measurement accuracy of the position of the axis C2 of the female thread 31 can be further improved.

[0056] The effective diameter d2 of the male thread 12 in the shaft portion 11 is preferably smaller than the minimum value D2min of the effective diameter D2 of the female thread 31 in the standard S. Thereby, it is possible to easily fit the male thread 12 to the female thread 31.

[0057] The effective diameter d2 of the male thread 12 in the shaft portion 11 is preferably equal to or greater than the minimum value D1min of the inner diameter D1 of the female thread 31 in the standard S. In this case, since the contact area between the flanks 13 and 33 of the male thread 12 and the female thread 31 can be ensured, the play between the female thread 31 and the measuring tool 10 can be further suppressed, and their coaxiality can be easily reduced. Therefore, the measurement accuracy of the position of the axis C2 of the female thread 31 can be further improved.

[0058] A male screw 31 conforming to Standard S, for the male screw 31 with a nominal diameter of M10 and a pitch P of 1.25 in Table 1 above, measuring tools 10 for Samples 1 to 5 with each dimension of the female screw 12 adjusted are illustrated in Table 2 below.

Table 2

[0059] Table 2 further shows Tmax and Tmin for each of Samples 1 to 5. In the "Condition of the pitch diameter" in Table 2, when the pitch diameter d2 is equal to or greater than the minimum value D1min = 8.647 of the inner diameter D1 of the male screw 31 in Standard S, it is marked as "〇", and when it is less than the minimum value D1min, it is marked as "×". In the "Condition of the number of rotations" in Table 2, when both Tmax is 4 or less and Tmin is 2 or more are satisfied, it is marked as "〇", and when at least one of them is not satisfied, it is marked as "×".

[0060] In Samples 1 to 3, since both the "Condition of the pitch diameter" and the "Condition of the number of rotations" are "〇", the working efficiency of attaching the measuring tool 10 to the male screw 31 can be improved, and the measuring accuracy of the position of the axis C2 of the male screw 31 can be further improved. For Sample 4 compared to Samples 1 to 3, since the "Condition of the pitch diameter" is "〇" and the "Condition of the number of rotations" is "×", although it is somewhat inferior to Samples 1 to 3, the working efficiency of attaching the measuring tool 10 to the male screw 31 can be improved, and the measuring accuracy of the position of the axis C2 of the male screw 31 can be improved to a certain extent. Also, for Sample 5, since the "Condition of the pitch diameter" is "×" and the "Condition of the number of rotations" is "〇", although it is somewhat inferior to Samples 1 to 3, the measuring accuracy of the position of the axis C2 of the male screw 31 can be improved to a certain extent.

[0061] As described above, the present invention has been described based on the embodiments. However, the present invention is not limited to the above embodiments at all, and it can be easily inferred that various improvements and modifications are possible without departing from the gist of the present invention. The shape, dimensions, etc. of each configuration described in the above embodiments may be changed as appropriate. For example, the outer diameter 2R of the plug portion 15 may be smaller than the outer diameter d of the female screw 12 or the outer diameter of the handle portion 17, or may be the same as them.

[0062] Regarding the above embodiment, the handle portion 17 may be omitted. Also, the positions of the plug portion 15 and the handle portion 17 may be reversed. The shaft portion 11, the plug portion 15, and the handle portion 17 do not necessarily have to be coaxial. However, the smaller the coaxiality between the shaft portion 11 or the plug portion 15 and the handle portion 17, the easier it is to rotate the measuring tool 10 with the handle portion 17.

[0063] In the above embodiment, the case where the shaft portion 11, the plug portion 15, and the handle portion 17 are integrally molded has been described, but it is not necessarily limited to this. The shaft portion 11, the plug portion 15, and the handle portion 17 formed from separate members may be connected by welding, an adhesive, a fastening member, or the like. However, it is preferable that the shaft portion 11 and the plug portion 15 are integrally molded by cutting or the like from the same shaft-shaped member. In this case, compared with the case where the shaft portion 11 and the plug portion 15 are connected by post-processing, it is easier to reduce the coaxiality between the shaft portion 11 and the plug portion 15.

Explanation of Reference Numerals

[0064] 10 Measuring tool 11 Shaft portion 12 Female thread 15 Plug portion 31 Male thread C1 Axis (of the plug portion and the shaft portion) C2 Axis (of the male thread)

Claims

1. A measuring tool for measuring the axial center position of a female screw formed in accordance with a specific standard, A shaft portion having an outer circumferential surface on which an external thread is formed to be fitted into the internal thread; a cylindrical plug portion disposed coaxially with the shaft portion and connected to the shaft portion, The flank angle of the male thread in the shank portion is the same as the flank angle of the female thread in the specific standard, A measuring tool characterized in that the pitch of the male thread in the shank is different from the pitch of the female thread in the specific standard.

2. The flank angle of the male thread and the female thread is represented as θ, In the specific standard, the minimum value of the pitch diameter of the female thread is represented as D2min, the tolerance of the pitch diameter of the female thread is represented as TD2, and the pitch of the female thread is represented as P, When the effective diameter of the male thread in the shaft portion is represented as d2 and the pitch of the male thread is represented as p, (TD2+|D2min-d2|) / (|P-p|・tan2θ)≦4 2. The measuring tool according to claim 1, wherein the following is satisfied:

3. The flank angle of the male thread and the female thread is represented as θ, In the specific standard, the minimum value of the effective diameter of the female thread is represented as D2min, and the pitch of the female thread is represented as P, When the effective diameter of the male thread in the shaft portion is represented as d2 and the pitch of the male thread is represented as p, |D2min-d2| / (|P-p|・tan2θ)≧2 2. The measuring tool according to claim 1, wherein the following is satisfied:

4. 2. The measuring tool according to claim 1, wherein the pitch diameter of the male thread in the shank is smaller than a minimum value of the pitch diameter of the female thread in the specific standard.

5. 2. The measuring tool according to claim 1, wherein an effective diameter of the male thread in the shank is equal to or greater than a minimum value of an inside diameter of the female thread in the specific standard.

6. 3. The measuring tool according to claim 2, wherein the axial length of the male thread in the shank is four or more times the pitch of the male thread.

7. A method for measuring an axial center position of the female screw using the measuring tool according to any one of claims 1 to 6, comprising the steps of: an attachment step of screwing the male thread of the measuring tool into the female thread conforming to the specific standard until the corresponding male thread stops rotating; and a measuring step of measuring, after the attaching step, the axial positions of the plug portion and the shaft portion from an outer peripheral surface of the plug portion, and setting the axial position of the shaft portion to the axial position of the female thread.