The experimental research was conducted to find an end mill with an ideal helix angle, which has a superior anti-vibration effect and a low machining tolerance. A conventional endmill which all low blades are $30^{circ}$ helix angles and a different helix angle endmill which the opposite two blades are $30^{circ}$ and the other opposites are different helix angles were studied. The cutting farce, machining tolerance and surface roughness were obtained. The AE signals appeared to have low values in up-milling rather than in down-milling. These are also appeared to have low values at low spindle revolutions rates. The cutting force values of Fxy and Fxyz were found to be increased according to the value of helix angle. In up-milling, it was difficult to find a definite tendency in machining tolerance, but in down-milling machining tolerance of the different helix angle end mill was found to be lower than that of the convention end mill. There is a definite tendency that the surface roughness gets better as the RPM increases. In down-milling, Type A($25^{circ}$＋$30^{circ}$) appeared to bring the most satisfactory result.