RU2093322C1 - Screw tap manufacturing method - Google Patents

Abstract

FIELD: mechanical engineering. SUBSTANCE: this is used in tool production for relieving upper parts of sides of teeth in entering cone of screw tap. This relieving operation is performed separately by one-side grinding wheel preset for required thread profile angle. In operation, grinding wheel is moved along entering cone by axial feed. At relieving left-hand side of thread profile, axial feed value is selected to be lower than pitch of thread, and at relieving right-hand side of thread profile it is larger than pitch of thread. Given in description are formulas for determining aforesaid feed values depending on pitch of thread, angle of profile and angle of entering cone of screw tap. EFFECT: high efficiency. 2 dwg

Description

 The present invention relates to the field of metalworking, namely to tool production.

 A known method of manufacturing a tap, in which separate grinding of the sides of the teeth of the intake and calibrating parts is carried out. The backing is carried out on thread grinding machines equipped with a special device and two cams for separate backing of the intake and calibrating parts (see, for example, Matveev V.V. Cutting of exact threads. M. Mechanical Engineering, 1968).

 The disadvantage of this method is the inability to manufacture taps with different sizes of backing along the height of the sides of the profile of the teeth of the intake part. Meanwhile, taps, in which the upper parts of the lateral sides of the teeth of the intake part are made with a backing larger than the lower parts, provide a sharp increase in tool life by reducing the friction of the working surfaces on the material being processed.

 A known method of manufacturing a tap, which is the prototype of the proposed solution, in which, in addition to the main backing of the upper parts of the sides of the teeth of the tap, the upper parts of the sides of the teeth of the intake part are milled with a multi-grinding grinding wheel tucked onto a cone with an angle equal to the slope of the tap intake part. The width of the peripheral working sections of the circle is selected depending on the pitch of the thread (see, for example, AC N 1537430).

The known method has significant disadvantages:
the difficulty in maintaining the width of the peripheral sections of the circle when refueling on a cone;
a change in the width of these sections during wear of the circle, and therefore there is a need for re-rolling the thread onto the circle and refueling it onto the cone. The fundamental impossibility of maintaining a constant neck height h on all teeth of the tap thread. If the backing height was set on the first tooth of the tap thread, for example, equal to h = a, then on the second tooth it will be h = 2a on the third tooth h = 3a, etc. With the number of feathers of the tap Z on the last tooth of the tap thread, the height of the backing will be h = Z • a. That is, with the known method, the height of the neck on the teeth of the tap thread can only be variable.

где S шаг резьбы, мм;
ε угол профиля резьбы, град.To increase the productivity and manufacturing quality of the tap was made possible by using a method in which the upper parts of the sides of the teeth of the taper intake tap are ground with a grinding wheel, while their grinding is performed separately with a single-thread circle tucked at the angle of the thread profile, which is moved along the intake cone during grinding the left side of the thread profile with the axial feed S _{1 is} less, and the right side of the profile with the feed S _{2 is} greater than the thread pitch, and the feed limit from dependencies:

where S is the thread pitch, mm;
ε angle of the thread profile, deg.

 v angle of the intake cone of the tap, deg.

 In FIG. 1 shows a pattern of backing of the left sides of the profile of the teeth of the intake cone of the tap; FIG. 2 shows a pattern of backing of the right sides of the same teeth.

Section l ₁ represents the intake, and section l _{2 the} calibrating parts of the tap 1. The tap cone is made with an angle v. The teeth of the tap have a profile angle e. The grinding wheel 2 is tucked at the same angle.

 In order to increase the resistance of the tap, on the lateral sides of the teeth of the intake cone between the outer and middle diameters at a height h, backing was performed with a value greater than the backing of these teeth along the average diameter of the tap.

 Initially, the tap, as in the known method, zatylivaet on the sides of the cutting teeth of the intake part and the sides of the calibrating teeth. Backing is carried out as with conventional taps on a thread grinding machine with a single-thread circle using a special cam. The angle of the profile of the circle is taken equal to the angle of the profile of the cut thread. The value of the feed is taken equal to the size of the step of the backed thread. Then the tap is backed up along the outer diameter of the teeth of the intake part to form trailing corners like conventional taps. After that, the upper parts of the lateral sides of the teeth of the intake part are hardened at a height h.

According to the proposed method, this backing is carried out in a single-circle circle, with a profile angle equal to the angle of the thread profile, separately of the right and left sides of the teeth. To do this, the grinding wheel is installed at the beginning of the intake cone at the desired height h of the tooth backing and move it along the intake cone. When grinding the left side of the tooth profile, the value of the axial feed S ₁ , take less, and when grinding the right side of the profile, the feed value S ₂ take more than the thread pitch.

где S шаг резьбы, мм;
ε угол профиля резьбы, град.The feed rates are determined from the dependencies:

where S is the thread pitch, mm;
ε angle of the thread profile, deg.

 v angle of the intake cone, deg.

In contrast to the known method of manufacturing a tap, the proposed method provides:
improving the quality of the manufacture of the tap due to the ability to withstand the specified height of the backing on all the teeth of the tap thread;
increasing labor productivity by reducing the complexity of the process of editing the circle and adjusting the backing operation;
automation of obtaining the required size of the teeth of the tap.

The proposed method is easily implemented on a thread grinding machine with a standard grinding wheel. To implement the method, it is only necessary to correctly determine the feed rates S ₁ and S ₂ depending on the thread pitch, thread profile angles, and tap intake cone according to the above dependencies.

 Below is the rationale for choosing these innings.

The rationale for the choice of feed S ₁ .

The amount of feed S ₁ when grinding the left sides of the teeth is determined from the grinding scheme shown in FIG. one.

To ensure the backing at a constant height h, the same for all the teeth of the tap intake without distorting the profile of the tap teeth, the top of the circle should move from point D to point D ₁ . The necessary movement of the circle in the direction perpendicular to the axis of the tap is provided by a carbon ruler mounted on the wall at an angle equal to the angle of the intake cone v.

Axial movement of the circle along the axis of the tap from point C to point C _{1 is} achieved by installing on the thread grinding machine a feed per revolution of the tap equal to CC ₁ S ₁ . It is from geometric constructions.

In accordance with the circuit of FIG. 1 S ₁ CC ₁ BB ₁ - B ₁ C ₁ + BC.

From FIG. 1 segment BB ₁ is equal to the thread pitch i.e. BB ₁ S.

Find the segment B ₁ C ₁ . From the right-angled triangle B ₁ C ₁ D ₁ , in which the angle at the vertex D ₁ is equal to half the angle of the thread profile, we have B ₁ C ₁ B ₁ D ₁ sin 0.5 e.

Тогда

Аналогично находит отрезок BC. Из прямоугольного треугольника BCD: BC BD Sin 0,5 ε. Из косоугольного треугольника BDE:

С учетом проведенных вычислений получаем выражение для S₁:

После преобразований получаем выражение для подачи S₁:

Обоснование выброса подачи S₂.In the oblique triangle B ₁ D ₁ E _{1, the} angle at the apex B _{1 is} also equal to half the angle of the thread profile 0.5 e, and the angle at the apex E ₁ is (90 v), leg B ₁ E ₁ B ₁ F ₁ + E ₁ F ₁ where E ₁ F ₁ h, where h is the height of the teeth of the intake cone on which the backing is carried out. From a right-angled triangle AB ₁ F ₁ B ₁ F ₁ AB ₁ • tg v or taking into account that AB ₁ 2 S
B ₁ F ₁ = 2StgΦ.
Then B ₁ F ₁ = 2StgΦ + h.
In the oblique triangle B ₁ D ₁ E ₁

Then

Similarly, finds the segment BC. From a right triangle BCD: BC BD Sin 0.5 ε. From the oblique triangle BDE:

Based on the calculations, we obtain the expression for S ₁ :

After the transformations, we obtain the expression for the feed S ₁ :

Substantiation of discharge feed S ₂ .

The amount of feed S ₂ when grinding the right lateral sides of the teeth of the intake part of the tap is determined from the pattern of grinding shown in FIG. 2 by analogy with the above calculations.

According to the feed circuit S ₂ CC ₁ BB ₁ + B ₁ C ₁ BC. The line BB ₁ is equal to the thread lead BB ₁ S. It is required to find the lines B ₁ C ₁ and BC.

Find the segment B ₁ C ₁ . From the right triangle B ₁ C ₁ D ₁ , in which the angle at the vertex D ₁ is equal to half the angle of the thread profile 0.5ε, we have
B ₁ C ₁ = B ₁ D ₁ • sin 0.5ε.

Find the value of B ₁ D ₁ from the oblique triangle B ₁ D ₁ E ₁ . In it cathet
B ₁ E ₁ B ₁ F ₁ + E ₁ E ₁ ,
E ₁ F ₁ h,
B ₁ F ₁ = 2S • tgΦ
Then B ₁ E ₁ = 2S • tgΦ + h
Express the desired value of B ₁ D ₁ through the found leg of B ₁ E ₁ .

Поскольку углы

имеем

Тогда отрезок B₁C₁ будет равен:

Найдем отрезок BC.From an oblique triangle B ₁ D ₁ E ₁ :

Since the corners

we have

Then the segment B ₁ C ₁ will be equal to:

Find the segment BC.

It is similar to segment B ₁ C ₁ . From a right triangle BCD: BC = BD • sin 0.5ε.

Находим величину подачи S₂.Find the value of BD from the oblique triangle BDE:

Find the feed rate S ₂ .

За счет осуществления указанных приемов и использования подачи S₁ и S₂ обеспечивается автоматизация процесса затылования зубьев на заборной части метчика с высокой точностью, стабильностью и производительностью.S ₂ BB ₁ + B ₁ C ₁ BC
Substituting the expressions of the terms of the segments, after the transformations, we obtain the desired feed expression:

Due to the implementation of these methods and the use of feed S ₁ and S ₂ , the process of grinding the teeth on the intake part of the tap is automated with high accuracy, stability and performance.

Claims (1)

A method of manufacturing a tap, in which the upper parts of the flanks of the teeth of the intake cone of the tap are milled with a grinding wheel, characterized in that they are milled separately with a single thread circle, tucked at the angle of the thread profile, which is moved along the intake cone when the left side of the tooth profile is axially dimensioned the feed S _{1 is} less, and the right side of the profile with the feed S _{2 is} greater than the thread pitch, and the feed is determined from the dependencies

where S is the thread pitch, mm;
ε is the angle of the thread profile, deg;
Φ - angle of the intake cone of the tap, deg.

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