A 6-high, 3-tandem precision rolling mill was designed and manufactured for a specific purpose of rolling the coelinver for power spring of wrist watches, at the required precision in thickness of product within ±1 μ at 0.1mm thickness. Special attentions were paid for the satisfaction of the requirements, namely, (1) the elastic deformation of the housing and rolls of rolling mill during rolling must be small, (2) the tension imposed upon and the speed of motion of the material must be automatically controlled with accuracy, (3) major parts of the mill must be finished as precisely as possible, (4) a number of pairs of AC motors and hydraulic torque converters must be employed as a power source.
An excellent yield of 98% was obtained at the practice run by the trial mill manufactured on the principles described above.
In the present report, the structure of the mill and the partial results of experiments obtained by the mill are discussed.

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In most cases, the inner surface of the inner ring of the roller bearing or the inner surface of bushings is ground by the roll type centerless internal grinder.
In this case, the work is held by 3 rolls and ground. Thus, the roll pressure imposed rdially on the work will restrict the vibration of work and, as well, will provide the work with axial thrust in the direction of the support. In auto-gaging, the gage pressure will work in the direction counter to the thrust and, if the work moves minutely in the direction of the axis, eventually working accuracy will be greatly affected adversely. As correlativity between the gage pressure and dimension accuracy exists, the correlativity between the roll pressure and thrust was sought for in order to establish the gage pressure.

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On the centerless internal grinder whereon the work is supported on the outer surface by rolls and is ground, the pressure of the roll, which acts on the work, seriously affects on work accuracy. This paper will treat the relationship between the support rigidity and accuracy of work.
Pressure roll possesses the function of restricting the vibration of work and holds grave influence on work accuracy. That is :
(1) From the standpoint of work accuracy, it is favorable to have the load imposed on the pressure roll as heavy as possible to the extent that plastic deformation is not caused.
(2) Roundness of the outer and inner diameter possesses proportional relationship and will not vary due to the pressure of the pressure roll.
(3) Roundness will not be improved although the work is repeatedly ground.

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Experimental results on the residual stresses induced in metal cutting are presented in this paper. The residual stress is computed by Sachs's method and Heyn's one respectively. Effects of rake angle of cutting tool, cutting speed, depth of cut and feed are examined. In cutting of ductile materials, such as carbon steel, generally the compressive residual stress is found to be concentrated near the surface. The amount of the residual stress increases with decreasing rake angle of cutting tool, and with increasing depth of cut and feed. Cutting temperature seems to have little effect on the residual stress.

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Small holes of about 1mm diameter are easy to be drilled on a glass plate by electricaldischarge machining, but large holes or holes of intricate forms are difficult to. For the purpose of drilling these holes, the author has devised a method of cutting a glass plate by an electrode of Nickel wire and made fundamental experiments with it.
In this report, the cutting speed on a glass plate under various conditions is discussed.

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In the electro-discharge machining, the discharge current is usually oscillatory. But the majority of energy which is discharged from charged condenser is dissipated in the first half cycle of the discharge current, so even if the second half cycle (which is reverse polarity) of the discharge current were stopped by germanium rectifiers, the ratio of electrode-wear (=wear of cathode/that of anode) does not decrease so much.
According to the results of the experiments made on various metals of anode and cathode respectively, an alloyed cathode metal having higher value of thermal conductivity, vaporizing point and latent heat of vaporization, has smaller ratio of the electrode-wear. Furthermore, a cathode metal which contains lower value of work-function has smaller ratio of electrode-wear. In the case of ferromagnetic cathode metal, the ratio of electrode-wear is getting higher value by longitudinal magnetic field.

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