An erosion mechanism of the electric discharge machining process has been studied on a view-point of a cathode phenomena. The T-F theory was applied to the electron emission from a cathode in this method and the electron current density at a cathode spot was calculated from that theory and the Mckeown's relation. Then the energy distribution between the gap electrodes was found to be mainly decided by the positive ion current density at a cathode.
The electrode erosion of various materials was measured. It became clear from the results that the electrode erosion per one discharge is dependent on three elements of energy, discharging duration and its thermal property. The kind of the tool electrode materials has a relatively small effect upon machining speed while the erosion of the tool electrode is widely changed by its thermal property.
The negative half cycle of the oscillatory discharging current in a condenser discharge was rectified by using a silicon power rectifier, but the erosion ratio of electrodes was not improved so much and in some cases it became worse than that by the oscillatory current.

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Although explosive forming, that, is high-energy and high strain rate forming Process. started as an experimental-process a couple of years ago, it has now grown to be on a production scale in several plants.
In the previous report, we confirmed the basic data concerning the explosive forming.
In this paper, we assessed the practical value of this procces based on above results. Series of experiments were made with the metal die, shown in Fig. 2, and reinforced epoxy resine dies, shown in Fig. 3, 4, and condition of explosive forrnine. accuracy and strain distribution of products were studied.

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In the present paper the authors calculated the effects of the inclination of gear axis on the tooth profile error.
Due to the inclination of gear axis, the measuring surface of profile is inclined to the plane of rotation. Consequently the trace of feeler is deviated from true involute curve.
The amount of this deviation was studied theoretically.
In consequence we got following results.
(1) In the measurement of spur gear, said deviation is negligible, for instance in the case of inclination angle ψ=1°, module m=4 and tooth number z=18, the maximum error s is no more than 1.1μ.
(2) In the measurement of herical gear the inclination of gear axis has to be avoided, for the said deviation is of considerable amount.

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The constitution of an ultrasonic machining apparatus and the experimental results of its abilities are described in this paper. This apparatus is controled by a feed back loop from a pick up electrode on the horn, and has the following abilities.
1) Driving frequency of the vibrator always follows automatically as the machining load varies.
2) The input power of the vibrator or the amplitude in machining time is held constant independently of the variation of machining load.

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It is common experience that threaded fastenings can be loosened by vibration even though they are initially tight.
In order to know the mechanism of the relaxation of threaded fastenings, the experiments were carried out by using a newly designed "repeated load test machine", on which the bolt to be tested was tightened on the seats.
The tightening force were measured by strain gauge pasted on the bolt tee tested.
As the experimental result, the mechanism of the relaxation of threaded fastening was clarified to some extent and the authors recommend the value of 0. 20. 5 for the coefficient of friction between bolt and nut.
Furthermore, the relaxing characteristic of threaded fastening under repeated load was formulized by some theoretical considerations.

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