Metal deforming – By use of tool acting during relative rotation between tool... – Tool orbiting or rotating about an axis
Patent
1982-02-18
1985-01-01
Husar, Francis S.
Metal deforming
By use of tool acting during relative rotation between tool...
Tool orbiting or rotating about an axis
72 98, 72103, 10152T, B21H 308
Patent
active
044910029
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The invention relates to the art of metal working by pressure, and more particularly it concerns methods and tools for forming on a workpiece resilient threads having a closed helical cavity inside the thread by plastic deformation of the metal in a cold state.
DESCRIPTION OF THE PRIOR ART
Methods of forming threads by plastic deformation of the metal of a workpiece, by rolling in particular, which have wide application in modern practice (see, for example, Pisarevsky M. I., Nakativanie tochnikh rezb i shlitsev, Moscow-Leningrad, Mashgiz, 1968), together with such obvious advantages as high productive capacity, metal saving and high precision of resulting threads, are characterized by substantial disadvantages. Among these are, first of all, a strict tolerance for the size of a workpiece to prevent jamming of the tool when forming a thread in bores, and considerable thread-forming forces acting on the tool, which is particularly unwanted when forming a thread in bores of small diameter (less than 8 mm).
Known in the art is a method of forming a resilient thread having a closed helical cavity inside the thread disclosed in Japan Pat. No. 48-20,977 published June 25, 1973.
The above method comprises performing a helical groove in a workpiece and subsequent plastic deformation of its walls by means of a thread-forming tool. As noted in the patent specification, the helical groove is formed so as to have a depth in the range of 1/2 of the depth of thread to the complete depth of thread, but not in excess.
To form a thread, the thread-forming tool is deepened in the tops of the helical groove deforming its walls, which results in obtaining a thread having a closed helical cavity inside the thread.
The thread thus obtained, by virtue of the closed helical cavity inside the thread, allows widening of the tolerance for the size of a workpiece, reduction of the thread-forming forces acting on the tool and elimination of jamming of the tool in the operation of rolling a female thread.
However, when deforming a helical groove having a depth in the range of half the depth of the thread being obtained to its complete depth but not in excess, the future cavity is positioned at the tops of the thread and is limited by the size of its projections. Moreover, the most intensive deformation of the workpiece material under the action of the thread-forming portion of the tool takes place at the tops of the thread, and the cavity turns out to be narrow. It prevents the substantial increase of the thread resilience, widening of the range of tolerance for workpiece size, and reduction of the torque in the rotation of the thread-forming tool in the operation of forming a thread.
Known in the art is a threading tool-screw tap for rolling in bores resilient thread having a closed helical cavity inside the thread as in USSR Inventor's Certificate No. 625,824 published Sept. 30, 1978.
This screw tap comprises a groove-forming portion and a thread-forming portion arranged in series and rigidly connected with each other. Projections of the thread of both portions have the same pitch and are displaced along the axis of the screw tap at least by half the pitch relative to each other, the major diameter of the projections of the groove-forming portion not exceeding the major diameter of the thread-forming portion.
To obtain a resilient thread having a closed helical cavity inside the thread, the screw tap is screwed in a bore. In doing so, the first (groove-forming) portion forms a groove having a depth within the range of half the depth of the thread being obtained to its complete depth. In subsequent motion of the screw tap, the thread-forming portion following the groove-forming portion deepens in the tops of the helical groove and deforms its walls, which results in forming a thread having a closed helical cavity inside the thread.
As in the above-described method, the volume of the cavity in the thread obtained by this screw tap is limited by the size of the projections of its thread because the helical groo
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Didyk Rostislav P.
Shamenko Stepan P.
Toropov Anatoly A.
Toropov Gennady A.
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