RU1819724C - Chipless tap - Google Patents

Abstract

Usage: metal forming, obtaining internal threads by cold plastic deformation. SUMMARY OF THE INVENTION: The tap comprises a conical intake portion, on which the tops and troughs of the threads are formed on generators mutually converging to the front end. One of the generators, bounding the tops of the thread turns along the outer diameter, belongs to a cone, the large base of which is located in the plane dividing the intake and calibrating parts of the tap. The forming, bounding hollows of the thread turns along the inner diameter, belongs to a cone, the small base of which is located in the said plane. 2 ill.

Description

The invention relates to mechanical engineering and can be used to produce internal threads by cold plastic deformation.

The aim of the invention is to improve the quality of the obtained threads by indicating the tops of the threads in the inner diameter (elimination of the crater) and to increase the tool life by reducing the deformation forces when rolling the tops of the threads in the inner diameter during the reverse stroke of the tap with the threads of the threads on the intake part .

In FIG. 1 shows the thread profile of the tap on the intake and part of the calibrating part and the profile of the formed thread in the forward stroke of the tap; in FIG. 2 - the same, with the reverse stroke of the tap.

In FIG. 1 and 2 the following notation is accepted:

dene - diameter of the hole for the thread;

D, d - respectively, the outer diameter of the thread and tap;

rg, dz - respectively, the average diameter of the thread and tap;

Di, di - respectively, the internal diameter of the thread and tap;

P-thread pitch.

The vertices 1 of the thread turns on the intake part are made parallel to the tap axis and are located along the generatrix 2 of the cone, the larger base of which is located in the transition plane 3. The cavities of the 4 thread threads on the intake part are also parallel to the tap axis and are located along the generatrix 5 of the truncated cone, the smaller base of which also located in the transition plane 3. The width of the threads of the threads on the inner diameter on the calibrating part of the tap is standard and can be determined by known dependencies for taps working on the principle of open loop. On the turns of the intake part, the width of the pads gradually increases from the transition plane to the front end of the tap. It

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Depends on the executive sizes of a tap and a tilt angle. In this case, the profile of the threads on the intake part is made different from the profile of the resulting thread and its angle must be greater than the profile angle of the standard thread. Moreover, the largest value of the angle is made at the first turn. Then, the profile angle gradually decreases, reaching the profile angle of the resulting thread at the first turn of the calibrating part of the tap. On the intake part, the taps are made with a number of threads to produce the corresponding threads (usually taps for through threads and taps for shearling blind threads). On the calibrating part, the hollows of the thread turns are made as with taps designed to receive threads with an open loop, i.e. during threading, the internal diameter of the gauge portion is not involved in the formation of the vertices of the threads.

The tap works as follows. - In the direct course, the first turn of the fence

part begins to penetrate into the metal and

pushes a helical groove in it. Extruded metal flows along the sides of the profile. Since the tension on the first turn is small and the threaded groove is just beginning to form, the plastic zone is small and does not reach the site in terms of inner diameter. When the next turns of the thread of the intake part come into operation, the height of the formed thread profile increases, the threaded groove deepens. The threads of the thread of the calibrating part of the tap finally form a thread profile with an open loop (i.e., the tops of the threads of the thread of the inner diameter are not deformed by the inner diameter of the threads of the thread of the tap of the calibrating part and they remain with the boat. When the thread is reversed, the mark of the thread of the thread turns on the intake part gradually begins deform the tops of the turns of the obtained thread, rolling the formed crater. The site starts on the transitional loop first. Gradually, the remaining sites also come into operation, the final diameter of the threads obtained by the inner diameter. The size of the obtained thread by the inner diameter is determined by the size at which the first (from the front end) of the tap area on the inner diameter is made. This size can be made so as to ensure that the thread has an inner diameter within specified in the thread standard Nominal inside diameter DI defined 5 0

5

0 5 0. 5 0 5

is made for metric threads GOST 24705-81, the tolerance on it is GOST 16093- 81. In order for the inner diameter of the thread to be guaranteed to be in the tolerance field, the inner diameter of the tap on the first (from the end of the tap) turn should be equal to ch + e / 2. Then the angle of inclination p of the troughs of the threads of the inner diameter can be determined by the following relationship

(n-l) / .-- where e is the tolerance on the internal diameter of the thread, mm;: -.

P - thread pitch, mm;

p - the number of threads on the intake part of the tap,

The use of the proposed tap allows you to get a higher quality thread than conventional chipless taps, because the resulting thread always has an inner diameter of & tolerance and without crater on the tops of the turns. Unlike chipless taps, operating on the principle of a closed loop, the proposed tap first forms a thread profile (with a forward stroke), and then closes the contour (rolls a crater - with a reverse stroke). This separation significantly reduces the load on the tap during thread formation, which increases tool life. The technology for making taps is also simplified. there is no need to use special copy rulers for profiling the intake part of the tap. The tap can be made on a multi-thread grinding machine.

Claims (1)

Formula of the invention A chipless tap containing a conical intake and calibrating parts with an incomplete profile height, which is included in that, in order to improve the quality of processing and increase durability by reducing the deformation force during for machining the threads along the inner diameter, the peaks and troughs of the thread profile are located on the generators mutually converging to the front end of the tap, and the forming, bounding the tops of the turns of the thread profile in the outer diameter, belongs to the cone, a large base which is located in the transition plane between the intake and gauge parts, and the generatrix, which limits the hollows of the turns of the threaded profile along the inner diameter, belongs to a cone, the smaller base of which is located in the said plane. Nut ZoShawn part Editor  Fm.2 Compiled by S. Rickman Tehred M. Morgenthal / ymu $ umshchd Vffc / ffb Corrector; M. Keretsman