Method for manufacturing external thread with reduced pitch diameter based on standard metric external thread

Abstract

The invention discloses a method for manufacturing an intermediate-diameter-reduced external thread based on a standard metric external thread. The method comprises the steps that a finished bolt meeting the standard metric thread standard serves as a standard bolt to be used for manufacturing an intermediate-diameter-reduced bolt; according to the fact that the pitch diameter of the thread is equivalent to the diameter of the thread rolling blank, the diameter d 'P = dP-deltad2 of the thread rolling blank of the bolt with the reduced pitch diameter is obtained through calculation; calculating the difference value delta VP between the volume V1 of the thread rolling blank of the standard bolt and the volume V2 of the thread rolling blank of the reduced pitch-diameter bolt according to # imgabs0 #; the thread cutting depth delta d is calculated according to delta VP = delta V = F (delta d); the thread cutting depth delta d serves as the turning depth, the original thread outer circle of the standard bolt is turned, and a semi-finished product bolt is obtained; and performing thread rolling on the semi-finished product bolt according to the original thread lines on the semi-finished product bolt, and obtaining the bolt with the reduced pitch diameter after surface treatment is completed. The small-pitch-diameter bolt can be manufactured and machined through the finished bolt, the production process is simplified, and the production efficiency is improved.

Description

Technical Field

[0001] The invention relates to the technical field of fastener manufacturing, and in particular to a method for manufacturing a reduced-mid-diameter external thread based on a standard metric external thread. Background Art

[0002] The fasteners in standard parts mainly include bolts, nuts, etc. In general, bolts and nuts are mainly connected by threads. The thread profiles are divided into triangular threads, rectangular threads, trapezoidal threads and serrated threads. Among them, the most commonly used thread profile is triangular thread, and the most commonly used external thread tolerance is 6g. Bolts with standard metric threads usually have good interchangeability, complete specifications on the market, and are easy to purchase. However, for some users' requirements for bolts with reduced mean diameter (reducing the mean diameter of standard metric threads), they are non-standard bolts, and products on the market usually cannot meet the technical requirements.

[0003] In the prior art, the production of bolts with reduced center diameter generally includes the following processes: cutting → beating → turning → thread rolling / thread rubbing → heat treatment → surface treatment. This production process has good cost control for large-volume orders, but for small and medium-volume orders, this process is particularly complicated, not only with low production efficiency but also high cost. Summary of the invention

[0004] In view of this, the present invention provides a method for producing reduced middle diameter external threads based on standard metric external threads with a tolerance of 6g and a thread profile of 60° triangle. The method can realize the production and processing of reduced middle diameter bolts using finished bolts, simplify the production process and improve production efficiency.

[0005] The present invention is implemented by the following technical solution: A method for manufacturing a reduced-diameter external thread based on a standard metric external thread comprises the following steps:

[0006] Step 1: Measure the thread pitch diameter and major thread diameter of the finished bolt, and compare them with the standard. The finished bolts that meet the standard metric thread standard are used as standard bolts to make bolts with reduced pitch diameter;

[0007] Step 2: Know the thread rolling blank diameter d of the standard bolt P , the reduction in the mean diameter is Δd2. Since the mean diameter of the thread is equivalent to the diameter of the thread rolling blank, it can be known that the reduction in the diameter of the thread rolling blank is Δd P =Δd2, calculate the thread rolling blank diameter d' of the reduced mid-diameter bolt P =d P -Δd2;

[0008] Step 3: According to Calculate the difference ΔV between the volume V1 of the thread rolling blank of the standard bolt and the volume V2 of the thread rolling blank of the reduced pitch diameter boltP , where L is the known standard metric thread length;

[0009] Step 4: Difference ΔV P The thread cutting volume ΔV is the same as the thread cutting volume ΔV that needs to be removed on the outer circle of the original thread of the standard bolt. The thread cutting volume ΔV is a one-dimensional function F(Δd) of the thread cutting depth Δd. P =ΔV=F(Δd) to calculate the thread cutting depth Δd;

[0010] Step 5: Using the thread cutting depth Δd as the turning depth, turning the outer circle of the original thread of the standard bolt to obtain a semi-finished bolt;

[0011] Step 6: According to the original thread pattern on the semi-finished bolt, roll the thread and complete the surface treatment to obtain the reduced diameter bolt.

[0012] Furthermore, in step 4, the univariate function F(Δd) is: Among them, D0 is the major diameter of the original thread, P is the standard metric thread pitch, and H is the original triangle height of the standard metric thread.

[0013] Furthermore, in step 2, the thread rolling blank diameter d of the standard bolt p Utilize d P =D-0.695P, where D is the nominal diameter of the standard metric thread.

[0014] Furthermore, in step 2, the thread rolling blank diameter d of the standard bolt p Utilize d P =d2, where d2 is the average mid-diameter of the finished bolt thread.

[0015] Furthermore, in step 4, D0 is taken as the nominal diameter D of the standard metric thread.

[0016] Furthermore, in step 4, the value of D0 is taken as the average value d of the major diameter of the finished bolt thread.

[0017] Compared with the prior art, the present invention has the following beneficial effects:

[0018] 1. The present invention is based on the equal volume method, that is, ΔV P =ΔV, the finished bolts are modified to reduce the middle diameter bolts, which reduces the cutting, hammering and heat treatment links, simplifies the production process and improves the efficiency; and does not damage the heat treatment performance of the original workpiece, and protects the mechanical properties of the workpiece to the maximum extent.

[0019] 2. The present invention is flexible and adjustable for different mid-diameter reduction amounts, and can calculate the original thread cutting depth, so it has universal applicability.

[0020] 3. The method of the present invention has high calculation accuracy and is low-cost and fast for small and medium batch customization of reduced diameter bolts. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 A flow chart of a method for producing external threads with reduced mid-diameter.

[0022] Figure 2 Flow chart for calculating the cutting depth of the external thread.

[0023] Figure 3 Comparison chart of standard bolts and reduced diameter bolts.

[0024] Figure 4 Schematic diagram of thread outer circle cutting depth. DETAILED DESCRIPTION

[0025] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0026] The present invention provides a method for manufacturing a reduced middle diameter external thread based on a standard metric external thread, wherein a reduced middle diameter external thread with a middle diameter reduction amount of Δd2 is manufactured for a standard metric external thread with a tolerance of 6g and a tooth profile of 60° triangle, and the pitch of the reduced middle diameter external thread is the same as the pitch of the original standard metric external thread, such as Figure 1 As shown in FIG. 3, the method comprises the following steps (the following data units are all mm, and the following threads all refer to external threads):

[0027] Step 1: Measure the pitch diameter and major diameter of the finished bolt. The pitch diameter can be measured with a pitch micrometer and the major diameter can be measured with a vernier caliper. Compare the measured pitch diameter and major diameter of the finished bolt with the standard GB / T15756-2008 (limit size of ordinary threads) or the standard GB / T197-2018 (tolerance of ordinary threads) to check whether the pitch diameter and major diameter of the finished bolt meet the standards of standard metric threads. Only finished bolts that meet the above standards can be used as standard bolts to make reduced pitch diameter bolts.

[0028] Step 2: The required thread diameter reduction of the bolt is Δd2 compared to the standard metric thread. The required thread diameter reduction of the bolt is in is the standard metric thread pitch diameter; since the thread pitch diameter is similar to the thread rolling blank diameter, the thread pitch diameter d'2 of the reduced pitch diameter bolt is equivalent to the thread rolling blank diameter d' of the reduced pitch diameter bolt PIt can be seen that the reduction in the mean diameter Δd2 is approximately the reduction in the diameter of the thread rolling blank Δd P , calculate the thread rolling blank diameter d' of the reduced mid-diameter bolt P =d P -Δd P =d P -Δd2,d P It is the thread rolling blank diameter of the standard bolt.

[0029] Standard bolt thread rolling blank diameter d P is a known number, and its value is obtained according to the standard GB / T 18685-2017 (diameter of the blank before ordinary thread rolling and rolling). The thread rolling blank diameter is the diameter of the thread rolling blank processed by the bolt before thread rolling, and the thread rolling is formed by extruding the thread rolling blank using a thread rolling wheel.

[0030] Step 3: Calculate the difference ΔV between the volume V1 of the thread rolling blank of the standard bolt and the volume V2 of the thread rolling blank of the reduced diameter bolt according to formula (1): P :

[0031]

[0032] Where L is the known standard metric thread length.

[0033] Step 4: During the thread rolling process, no solid material is removed, that is, the volume of the thread rolling blank of the bolt is the same as the volume of the bolt made from it. It can be obtained that the volume of the thread rolling blank of the reduced pitch diameter bolt is the same as the volume of the reduced pitch diameter bolt. In other words, the difference between the volume of the standard bolt and the volume of the reduced pitch diameter bolt is equal to the difference ΔV between the volume of the thread rolling blank of the standard bolt V1 and the volume of the thread rolling blank of the reduced pitch diameter bolt V2 P . Make the difference ΔV P It is the same as the thread cutting volume ΔV removed on the original thread outer circle of the standard bolt, that is, the volume after removing ΔV on the original thread outer circle of the standard bolt is the same as the volume of the bolt with reduced mid-diameter.

[0034] The thread cutting volume ΔV is a univariate function F(Δd) of the thread cutting depth ΔΔd, and is calculated by formula (2) at the thread cutting depth ΔΔd:

[0035] ΔV P =ΔV=F(Δd) (2);

[0036] The univariate function F(Δd) is derived from the volume of the thread portion that needs to be removed by cutting on the outer circle of the original thread. This portion is a helical structure. The volume of the thread portion that needs to be removed by cutting can be obtained by calculating the volume of the helical structure. The width of the helical structure, i.e., the thread cutting depth ΔΔd, is known. The rest of the data are known. Formula (3) is derived:

[0037]

[0038] Among them, D0 is the major diameter of the original thread; P is the standard metric thread pitch, and H is the original triangle height of the standard metric thread. Both P and H can be obtained by looking up the table of GB / T192-2003 (basic tooth profile of ordinary thread).

[0039] In specific implementation, according to the finished bolt situation, if the thread pitch diameter and thread major diameter of the finished bolt are almost the same as those of the standard metric thread, D0 can be taken as the standard metric thread nominal diameter D; or D0 can also be taken as the average value d of the thread major diameter of the standard bolt. Because only finished bolts that meet the standard requirements can be used as standard bolts to make reduced pitch diameter bolts, and the thread major diameter of the standard bolt meets the range required by the standard metric thread major diameter, the error of the results obtained by the two value-taking methods can be ignored.

[0040] Step 5: Figure 4 As shown, the thread cutting depth ΔΔd is used as the turning depth, and the original thread outer circle of the standard bolt is turned to obtain a semi-finished bolt; the volume of the semi-finished bolt is the same as the volume V2 of the thread rolling blank of the reduced middle diameter bolt, that is, the same as the volume of the reduced middle diameter bolt, and can be used to make the reduced middle diameter bolt.

[0041] Step 6: According to the original thread pattern on the semi-finished bolt, the thread rolling wheel automatically aligns along the original thread pattern, rolls the thread, and obtains a bolt with reduced mid-diameter after surface treatment.

[0042] Example 1

[0043] This embodiment further explains steps 2 and 4. After confirming that the thread of the finished bolt meets the standard metric thread by random inspection, the standard metric thread nominal diameter D and the standard metric thread pitch P can be used to calculate the thread rolling blank diameter d of the standard bolt. p and reduce the thread rolling blank diameter d′ of the mid-diameter bolt p , which can greatly reduce the tedious steps of measuring and testing the finished bolts and comparing them with GB / T18685-2017 to obtain the blank diameter. Step 2, through a large number of experimental measurements, the calculation formula for the standard metric thread rolling blank diameter is obtained. For the finished bolts that meet the standard metric thread standard, the thread rolling blank diameter d p It can also be calculated using formula (4):

[0044] d P =D-0.695P (4)

[0045] Where D is the nominal diameter of the standard metric thread, and P is the standard metric thread pitch;

[0046] Then reduce the thread rolling blank diameter d' of the medium diameter bolt p Using formula (5) we can calculate:

[0047] d' P =D-0.695P-Δd2 (5)

[0048] Among them, Δd2 is the reduction of median diameter;

[0049] In step 4, the standard metric thread nominal diameter D and the standard metric thread pitch P are substituted into formula (3), and D0 is taken as the standard metric thread nominal diameter D, and the result is:

[0050]

[0051] At this time, formulas (1)-(5) give:

[0052]

[0053] Simplifying gives:

[0054]

[0055] Among them, D, H, P, Δd2 are all constants, and the thread cutting depth Δd is obtained by solving. From the above calculation, it can be seen that the thread cutting depth Δd can be solved without knowing the standard metric thread length L.

[0056] For example, after testing, the thread diameter and major diameter of the finished bolt meet the standard of GB / T5783M30*100 with a tolerance of 6g and a pitch of 3.5mm for the standard metric thread. On this basis, a reduced diameter bolt with a reduced diameter of 0.3mm is made. Then, where D=30, H=3.03, P=3.5, Δd2=0.3, the final result is:

[0057] -4Δd 3 +87.73Δd 2 +68.18Δd-74.71=0

[0058] The thread cutting depth Δd=0.618 mm is obtained, that is, the outer circle of the thread of the finished bolt is turned away from the outer thread with a depth of 0.618 mm.

[0059] Example 2

[0060] This embodiment further explains steps 2 and 4. After confirming that the thread of the finished bolt meets the standard metric thread, the thread rolling blank diameter d of the standard bolt can be calculated using the average value of the pitch diameter of the standard bolt thread that meets the standard. p and reduce the thread rolling blank diameter d' of the mid-diameter bolt p .

[0061] Step 2: The bolt pitch diameter is approximately equal to the bolt thread rolling blank diameter. The thread rolling blank diameter d of the standard bolt is p The average value d2 of the thread diameter of the batch of standard bolts can be taken, and the thread rolling blank diameter d p Using formula (6), we can calculate:

[0062] d P =d2(6)

[0063] Then reduce the thread rolling blank diameter d' of the medium diameter bolt p Using formula (7), we can calculate:

[0064] d' P =d2-Δd2 (7)

[0065] Among them, Δd2 is the reduction in median diameter.

[0066] In step 4, the average value d of the major diameter of the standard bolt thread is substituted into formula (3), that is, D0 is taken as the average value d of the major diameter of the standard bolt thread, and the result is:

[0067]

[0068] At this time, formulas (1)-(3) and (6)-(7) give:

[0069]

[0070] Simplifying gives:

[0071]

[0072] Among them, d2, d, H, P, Δd2 are all constants, and the thread cutting depth Δd is obtained by solving.

[0073] For example, after testing, the thread diameter and major diameter of the finished bolts meet the standard of GB / T 5783M30*100 with a tolerance of 6g and a pitch of 3.5mm for standard metric threads, and can be used as standard bolts for the next step of production. The average d2 of the thread diameter of this batch of standard bolts is 27.55mm, and the average d2 of the major diameter of the thread is 29.78mm. Take d2=27.55, d=29.78, and make reduced diameter bolts with a reduced diameter of 0.3mm based on this batch of standard bolts, where H=3.03, P=3.5, Δd2=0.3, and finally:

[0074] -4Δd 3 +87.07Δd 2 +67.68Δd-74.66=0

[0075] The thread cutting depth Δd=0.621 mm is obtained, that is, the outer circle of the thread of the finished bolt is turned away from the outer thread with a depth of 0.621 mm.

[0076] The thread cutting depth Δd obtained in Example 1 and Example 2 of the present invention differs by 0.003 mm. Based on the standard metric thread nominal diameter D=30 mm, the error is 0.1‰, which can be ignored. Whether Example 1 uses the standard metric thread nominal diameter D and the standard metric thread pitch P for calculation, or Example 2 uses the average value d2 of the standard bolt thread middle diameter and the average value d of the thread major diameter, the turning cutting depth Δd can be obtained, and the errors of the results obtained by the two calculations are extremely small, and the accuracy of the results is high.

[0077] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for producing a reduced-diameter external thread based on a standard metric external thread, characterized in that: The following steps are involved: Step 1: Measure the thread pitch diameter and major thread diameter of the finished bolt, and compare them with the standard. The finished bolts that meet the standard metric thread standard are used as standard bolts to make bolts with reduced pitch diameter; Step 2: Know the thread rolling blank diameter d of the standard bolt P , the reduction in the mean diameter is Δd2. Since the mean diameter of the thread is equivalent to the diameter of the thread rolling blank, it can be known that the reduction in the diameter of the thread rolling blank is Δd P =Δd2, the diameter of the thread rolling blank d of the reduced mid-diameter bolt is calculated ’ P =d P -Δd2; Step 3: Calculate the difference ΔV between the volume V1 of the thread rolling blank of the standard bolt and the volume V2 of the thread rolling blank of the reduced pitch diameter bolt according to the following formula: P : Where L is the standard metric thread length; Step 4: Difference ΔV P The thread cutting volume ΔV is the same as the thread cutting volume ΔV that needs to be removed on the outer circle of the original thread of the standard bolt. The thread cutting volume ΔV is a one-dimensional function F(Δd) of the thread cutting depth Δd, and the thread cutting depth Δd is calculated by the following formula: ΔV P =ΔV=F(Δd); Step 5: Using the thread cutting depth Δd as the turning depth, turning the outer circle of the original thread of the standard bolt to obtain a semi-finished bolt; Step 6: According to the original thread pattern on the semi-finished bolt, roll the thread and complete the surface treatment to obtain the reduced diameter bolt.

2. The method according to claim 1, characterized in that In step 4, the univariate function F(Δd) is: Among them, D0 is the major diameter of the original thread, P is the standard metric thread pitch, and H is the original triangle height of the standard metric thread.

3. The method according to claim 2, characterized in that In step 2, the thread rolling blank diameter d of the standard bolt p Calculated using the following formula: d P =D-0.695P Where D is the nominal diameter of the standard metric thread.

4. The method according to claim 2, characterized in that In step 2, the thread rolling blank diameter d of the standard bolt p Calculated using the following formula: d P =d2 Among them, d2 is the average value of the thread diameter of the finished bolt.

5. The method according to claim 3 or 4, characterized in that In step 4, D0 is taken as the nominal diameter D of the standard metric thread.

6. The method according to claim 3 or 4, characterized in that In step 4, D0 is taken as the average value d of the major diameter of the finished bolt thread.

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