CN112756712B

CN112756712B - Method for machining tool withdrawal groove-free blind hole wave-shaped threads by using numerical control lathe

Info

Publication number: CN112756712B
Application number: CN201910999987.5A
Authority: CN
Inventors: 黄献萩; 张敏
Original assignee: Jsi Rock Tools Co ltd
Current assignee: Jsi Rock Tools Co ltd
Priority date: 2019-10-21
Filing date: 2019-10-21
Publication date: 2022-04-22
Anticipated expiration: 2039-10-21
Also published as: CN112756712A

Abstract

The invention discloses a method for machining a non-tool withdrawal groove blind hole wave-shaped thread by a numerical control lathe, and aims to provide a method for turning a non-tool withdrawal groove thread by a sharp cutter. Dividing the thread form into a plurality of cutting points according to the geometric shape of the thread form; sequentially taking each cutting point as a starting point, respectively cutting and feeding the blind holes, wherein the feeding distance of each time is equal to the length of the thread; taking the position after each feed is finished as the withdrawal starting point of the cutting, withdrawing the cutting to a preset end point in an inclined manner according to the direction forming an alpha included angle with the feed direction, and then quickly returning to the next cutting point until the thread cutting is finished for n times; alpha is more than 90 degrees and is more than or equal to 15 degrees. The method has the advantages of small cutting resistance and less cutter abrasion, and is a method for processing the thread without the tool withdrawal groove.

Description

Method for machining tool withdrawal groove-free blind hole wave-shaped threads by using numerical control lathe

Technical Field

The invention relates to a thread turning method, in particular to a method for processing a tool withdrawal free blind hole wave thread by a numerical control lathe; belongs to a method for machining blind hole threads in a turning mode.

Background

The wave thread is a mining thread for connecting a drill bit and a drill rod, and is generally processed by means of profiling machining, cyclone milling and the like at present. No matter which processing mode is adopted, a tool withdrawal groove is required to be arranged, otherwise, the cutting allowance of the tail end of the thread is suddenly increased, so that the tool tip is broken, or the processed thread is damaged. However, the relief groove reduces the fatigue life of the drill bit magazine, and if the relief groove can be eliminated, not only the bit life can be increased, but also the machining cost can be reduced.

With the popularization of numerical control machines, the machining of the blind hole threads without the tool withdrawal groove by utilizing the characteristic that the numerical control machines have accurate tail withdrawal amount becomes possible, but the machining is carried out by utilizing a forming cutter which is matched with a cutter point angle and a thread profile angle. For example, "CN 105345172A" discloses a method for processing internal threads of blind holes without tool withdrawal grooves, which utilizes a tool with a tool tip angle corresponding to the thread profile angle to process triangular threads. However, the use of a formed thread tool for threading not only has the defects of troublesome tool sharpening, large cutting resistance, easy reduction of thread precision caused by tool abrasion in the machining process and the like, but also needs to select an adaptive tool according to the thread form, and has various tool specifications and troublesome management. Therefore, the problems of large thread cutting resistance, serious tool abrasion and unstable thread quality in machining the blind hole without the tool withdrawal groove by using the numerical control lathe are to be solved urgently.

Disclosure of Invention

In order to overcome the defects in the prior art, the invention aims to provide a method for machining a corrugated thread of a blind hole without a tool withdrawal groove by using a numerical control lathe.

In order to achieve the purpose, the invention adopts the following technical scheme:

1) dividing the thread form into a plurality of cutting points Q according to the geometry of the thread form₁、Q₂……Q_n；

2) Sequentially using each cutting point Q₁、Q₂……Q_nAs a starting point, respectively cutting and feeding the blind hole by a sharp tool according to thread machining parameters, wherein the feeding distance L is₁、L₂……L_n= thread length L;

3) taking the position after the completion of each cutting feed as the tool withdrawal starting point T of the cutting_nThe cutter is inclined and retreated to a preset terminal point Z according to the direction forming an included angle alpha with the cutter feeding direction, and then the cutter rapidly returns to the next cutting point Q_nUntil the thread cutting is completed for n times; the preset terminal point Z is positioned on the bottom surface of the blind hole and the primary tool retracting starting point T₁Between the bottom surface (1) of the blind hole and the initial point T of one-time tool withdrawal₁The distance H between the two screw bolts is less than or equal to the distance C between the starting point of the external thread of the matched screw bolt and the front end surface of the screw bolt; alpha is more than 90 degrees and is more than or equal to 15 degrees.

The thread processing parameters comprise nominal diameter, thread bottom diameter, thread pitch and thread shape.

In the technical scheme, the more the number of the selected cutting points is, the higher the machining precision (such as smoothness) is, but the lower the machining efficiency is; therefore, the number and distribution of the cutting points can be comprehensively considered according to the precision requirement of the workpiece, the geometric shape of the tooth form and the combination of the processing efficiency. The cutting depth of each feed can be determined according to the precision requirement of a workpiece, the strength which can be borne by a cutter and the performance of a machine tool.

Compared with the prior art, the invention has the following advantages due to the adoption of the technical scheme:

1) because the inclined tool retracting mode is adopted, the thread form is not damaged;

2) the sharp cutter is used for cutting, so that the cutting resistance can be reduced, the abrasion of the cutter can be reduced, the thread processing quality can be improved, the specification of the cutter can be reduced, and the production management cost can be reduced.

Drawings

FIG. 1 is a schematic structural view of a wave thread of a blind hole of a drill bit;

FIG. 2 is a schematic view of the construction of a wave thread on a drill rod;

FIG. 3 is a schematic drawing of the machining of a blind wave thread.

In the figure: blind hole bottom surface 1, double-screw bolt front end face 2.

Detailed Description

The invention is further described with reference to the following figures and specific examples.

As shown in the figures 1-3, the specific operation steps are as follows:

2) At a first cutting point Q₁Taking the initial point as the starting point, respectively carrying out one-time cutting feed on the blind hole by using a sharp cutter according to thread machining parameters, wherein the one-time feed distance is L₁；

3) Taking the position after one-time cutting feed completion as the tool retracting initial point T of one-time cutting₁The cutting tool is inclined and retreated to a preset terminal point Z according to the direction forming an included angle alpha with the cutting feed direction, and then the cutting tool rapidly returns to a second cutting point Q₂Starting a secondary cutting feed at a position with a secondary feed distance of L₂(ii) a The preset terminal point Z is positioned on the bottom surface 1 of the blind hole and the primary tool retracting starting point T₁Bottom surface of blind hole1 and one-time tool retracting initial point T₁The distance H between the two screw bolts is not more than the distance C between the starting point of the external thread of the matched screw bolt and the front end surface 2 of the screw bolt, and the angle alpha is not less than 15 degrees and is more than 90 degrees;

4) according to the method of the step 3), sequentially using a third cutting point Q₃The fourth cutting point Q₄… … nth cutting point Q_nCutting feed is carried out on the blind hole for a starting point, the sharp cutter retreats to a preset end point Z after each feed is finished, then the sharp cutter quickly returns to the position of the next cutting point to start the next cutting feed until n times of thread cutting are finished, and the feed distance L of each feed is long₃、L₄……L_n= thread length L.

In the above-described embodiment, H.ltoreq.C is selected in order to ensure that the front end face 2 of the drill rod is in contact with the blind hole bottom face 1 of the drill bit during operation, so that the thread load can be reduced. In consideration of the tool retracting efficiency, alpha is more than or equal to 15 degrees and more than 90 degrees.

The thread forming parameters in the above embodiments include nominal diameter, thread root diameter, thread pitch, thread profile.

The method of the invention can be used for processing wave-shaped internal and external threads, trapezoidal internal and external threads and rectangular internal and external threads.

Claims

1. A method for processing a tool withdrawal free blind hole wave thread by a numerical control lathe is characterized by comprising the following steps:

3) taking the position after the completion of each cutting feed as the tool withdrawal starting point T of the cutting_nThe cutter is inclined and retreated to a preset terminal point Z according to the direction forming an included angle alpha with the cutter feeding direction, and then the cutter rapidly returns to the next cutting point Q_nTo a position ofFinishing the thread cutting for n times; the preset terminal point Z is positioned on the bottom surface (1) of the blind hole and the primary tool retracting starting point T₁Between the bottom surface (1) of the blind hole and the initial point T of one-time tool withdrawal₁The distance H between the two screw bolts is less than or equal to the distance C between the starting point of the external thread of the matched screw bolt and the front end surface (2) of the screw bolt; alpha is more than 90 degrees and is more than or equal to 15 degrees.

2. The method for machining the relief-free blind hole wave thread by the numerical control lathe as claimed in claim 1, wherein the method comprises the following steps: the thread processing parameters comprise nominal diameter, thread bottom diameter, thread pitch and thread shape.