Noboru Shinozaki

The Standard of Wheel Selection:Studies on Wear and Redress Life of Grinding Wheel (4th Report)

In the case that a suitable grinding wheel is used under the optimum grinding condition, the purpose of grinding operation is attained. Even if the optimum grinding condition is established, the reasonable grinding operation cannot be done, when the selection of wheel grade is mistaken. So in grinding operations, the problem of wheel selection becomes most important. In this paper, the standard of wheel selection is considered on the theoretical basis. The results obtained are as follows : (1) The suitable wheel grade for grinding operation is given byE=1/-k5elog {1-mrθrJB√d0√kρc√υl/0.95k4 qR wV} orZg=mrθrJB√d0√kρc√υl/0.95k3 qR wVWhere, E : the modulus of longitudinal elasticity, Zg : the symbol mark of wheel grade, k4 : a constant, k5 : a constant, mr : the rate of normal force to tangential force, q : a constant, Rw : the flowing rate into the work of heat, θc : the critical grinding temperature corresponding to the occurence of burn mark, J : the heat equivalent of work, k : the thermal conductivity of a workpiece, ρ : the density of a workpiece, c : the specific heat of a workpiece, do : average grain diameter, l : the contact arc length between a wheel and a workpiece, V : wheel speed, υ : work speed, B : the width of grinding.(2) The standard of wheel selection in case that the type of grinding and grinding conditions change can be obtained.

On Surface Roughness Generated by Rolling Tool

This paper describes some analyses and experiments about surface roughness generated by rolling tool. The results obtained are as follows. When the tool point is not located on the rolling center, surface roughness depends on n/N (n : number of tool rolling, N : number of work rotation). At n/N= i (i = 0, 1, 2, …) surface roughness becomes minimum, and at n/N= i+ 0.5 it becomes maximum, while except the case of n/N=i, i+ 0.5, waviness is generated generally. But when the tool point is just on the rolling center, surface roughness is not affected by rolling.

Thermal Stress Resistance of Ceramic and Carbide Tool Materials

酸素アセチレンガスと水道水により,周期的に加熱冷却を繰り返す装置を試作し,この装置により,セラミックチップ,カーバイドS2,G2,チップに温度サイクルを加えて割れを発生せしめ,つぎのような知見を得た,1.割れは冷却時に入る。2.同じ熱応力振巾を与えても,体積の大きなものは早く割れが入り,1og(1-1/n)=κV.なる関係が得られる。すなわち寸法効果が認められる。3.試料の受ける温度差が大きいほど割れは早く入り,log ln(n/n-1)=mlogtd+C3なる関係が得られ,チップの材質によつてmとC3の値が異なる。熱応力抵抗はセラミック→S2→G2の順に高くなる。4.熱応力により試料に発生する割れは,熱応力の大きさによつては数回ないし数十回の繰り返しが必要である。換言すれば一回の熱応力により割れの入る確率は小さい。5.熱応力が平面上どの方向にも一様であれば,割れの入る方向は,どの方向にも同じ確率である。6.以上の結果は実際の超硬正面フライス作業において,切れ刃面に生ずる割れの出現経過とよく対応する。7.この実験方法は,脆性物質の熱応力抵抗および一様性を測定する便利な方法であると考えられる。8.また各種のカーバイド材質について実際の正面フライス実験を行ない,その熱応力抵抗はS2→T2→T3→G2→H1の順に高くなることが認められた。