| Summary: | <p>Manufacturing observations of running machine taps show that a significant number of failures, as the breakages, arise from the threaded hole at the reverse. While a cutting part of the tap is inside the holes the chip roots, non-separated from the treated surface, remain there and under the reverse fall under the tooth relief with the main chip fragments, thereby leading to the tool failure.</p><p>Experience with chip-inside-taps (CIT) shows that their failures are less common than those of the standard design taps. This is due to the difference in structures of the cutting parts of taps. The teeth of the cutting part of CIT are shaped as a rigidly fixed cantilever beam the crosssection of which is a circular ring sector. Such shape of the teeth of CIT allows radially directed elastic deformation that reduces the effect of jamming the root and separating chips between the rear teeth surfaces of the tap and the treated surface and, as a consequence, reduces the force and the moment acting on the tool.</p><p>The reverse torque for standard taps and CIPs has been simulated. A device to simulate ingress of chip roots under the back surface of the taps has been developed. The effect of the chip root thickness at the moment of reverse has been experimentally studied using the high-speed standard taps and CIT sizes of M12x1.5. It has been found that for standard taps and CITs the moment of reverse under the same simulation conditions is nonlinearly dependent on the thickness of root chips and has a growing character. The reverse moment values for standard taps are up to four times more than those for CITs. This is to explain the fewer CIT failures observed during their operation.</p><p>Based on the experimentally obtained relationships, as the simulation results, a conclusion is proposed that it is expedient for the cutting part of taps to have elasticity to raise their efficiency.</p>
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