RU1815036C - Graded tap - Google Patents

Abstract

Usage: the tap improves the accuracy of the thread being cut by eliminating axial cuts and the stepping of the thread profile at feeds different from the thread pitch / SUMMARY OF THE INVENTION: The threaded part of the tap contains a rough 1 and final 2 steps. The average, inner and outer diameters of the threads of the roughing step 1 are smaller than the average, inner and outer diameters of the threads of the finishing step 2. In the case when, for example, the feed rate of the tap is less than the value of the thread pitch, the thread pitch of the roughing step 1 of the tap is performed larger than the thread pitch its finishing step 2 by the value of A P. Moreover, the lateral surface a of the teeth of the last thread of the draft tread 1 of the tap is a continuation of the lateral surface b of the teeth of its finishing step 2: 3 il.

Description

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The invention relates to metalworking, in particular to taps, and can be used in all engineering industries to increase the accuracy of thread machining with taps.

The purpose of the invention is to increase the accuracy of a thread cut by a tap by eliminating its stepping at feeds different from the thread pitch.

In FIG. 1 shows a general view of the tap; figure 2 is a thread profile of the rough and clean, howl tread of the tap; in Fig.3 is a diagram of the steps of the tap.

The tap thread consists of two successively arranged steps - draft 1 and finish 2. Each step has an intake cone. Medium (d24epH), inner and outer diameters of the thread of the draft tread of the tap are smaller than average (d24MCT). inner and outer diameters of the thread of the final stage of the tap. For cases, as shown in Fig. 2, when the tap feed is less than the thread pitch, the thread pitch of the taper roughing step is performed greater than the thread pitch of its finishing step by an amount AP, and the lateral surface a of the teeth of the last thread of the roughing tread of the tap facing the tap end, is a continuation of the corresponding lateral surface b of the teeth of its finishing step. A condition under which the lateral surface of the teeth of the last thread of the rough tread of the tap is a continuation of the corresponding lateral surface of the teeth of the final tread of the tap is 0.288 (d24MCT - d24epH). The value of D P is determined from the ratio

AR 0.577 (drcT - dfpH) - n + (1 ... 3)

where n is the number of threads of the thread of the tap on the roughing step if it was equal to the number of threads of the thread in the work hole (usually the number of threads of the thread of the tap in the rough step is less than the number of threads in the work hole);

Si and Za are metal cross-sections in the threaded grooves of the hole to be machined, removed with the teeth of the draft and finishing stages of the tap, respectively. 3, 4. 5 - the first thread of the thread, m - the last thread of the thread in the hole to be machined.

The tap works as follows. When entering the hole of its rough stage, at a feed not equal to the thread pitch (for example, a smaller pitch), the thread is axially cut, which leads to the formation of steppedness on the sides of the thread1 opposite to the cut, distortion of the thread pitch and taper formation. When entering the hole of the finishing step of the tap, the axial cutting by the teeth of this step is completely eliminated or sharply reduced. This is achieved by the fact that the ongoing axial thread cutting by the teeth of the taper roughing step with an increased thread pitch in relation to the operation of the teeth of its finishing step with a normal thread pitch is compensated by the increased axial displacement of the tap in the opposite direction due to the increased thread pitch on its rough step. Alignment of the reaction between the feed, a smaller thread pitch, and a larger axis

By moving the tap due to the increased thread pitch at its rough stage, it is ensured by the selection of the value of AP. As you enter the hole of the finishing step of the tap, the decreasing resistance to the feed, which is not equal to the thread pitch, due to the continuing exit of the teeth of the rough stage from the hole, is compensated by the increase in the number of surfaces L of the teeth of the finishing step

tap. The shift of the thread of the draft tread of the tap by 0.288 (02CLEAN - d24epH) towards the thread of the finishing step provides the final formation of the cut side of the thread in the hole

the sides b of the teeth of the finishing step of the tap and at the same time the complete removal of the steppedness of the thread profile in the hole formed by the teeth of the rough step on the threads 3, 4, 5 and other threads of the thread. Complete removal of steppedness as compared to the prototype tap is achieved in that for this tap, a part of the width of the teeth of the finishing step used to remove the steppedness of the thread profile is formed.

double-tooth teeth, twice as many. Calculation of А Р from the condition of dividing 0.577 (d24MCT- - d24epH.) By n + (1 ... 3) ensures that the thread profile in the hole ends with the teeth of the finishing step of the tap on the last thread of the teeth as well. The same effect is preserved when a value of P less than the calculated. Similarly, the tap works with a feed greater than the thread pitch. This tap eliminates

steppedness in the thread being cut at feeds different from the thread pitch provides a significant increase in the accuracy of thread cutting and the quality of the thread surface. ,

Claims (1)

The claims A stepped tap containing a threaded part consisting of a roughing and finishing steps, the middle, inner and outer diameters of the threads on the roughing step being smaller than on the finishing, different in that, in order to improve the accuracy of the thread being cut, the thread pitch of the taper roughing step is different from the threading step of the finishing step, while one of the tooth flanks of the last thread of the tapping roughing step is a continuation of the corresponding lateral surface of the teeth of the finishing step.