| 摘要 |
PURPOSE:To facilitate a change of a set value by indicating a ratio of an allowable set value of a cutting resistance of a drill to an actual cutting resistance value of the drill, in a device wherein a step feed is carried out based on the ratio of the allowable set value of the cutting resistance of the drill to the actual cutting resistance value of the drill. CONSTITUTION:An output shaft 1a of a motor 1 is connected with a main shaft 4 through a power transmission spring 2 and a spline shaft 3, a main shaft cylinder 8 supporting the main shaft 4 is advanced by an air cylinder 10 and a drilling process is made by a drill. When an actual cutting resistance value obtained through the quantity of torsion of the transmission spring 2 exceeds the maximum allowable set values, a step feed is carried out by switching a solenoid valve 13 and making the main shaft cylinder retreat. Then an indicator showing a ratio of the maximum allowable set value to the acutal cutting resistance value is provided and the maximum allowable set value is changed based on the indication of breakage of an edge of the drill detected by the indicator. |
