Abstract: A hand held power tool has a rotatable spindle, a tool holder arranged on the spindle, a tool inserted in the tool holder, locking members fixing the tool holder with the spindle and engaging both in the tool holder and the spindle, a rotatable ring holding the locking members in its locking position and provided with depressions for receiving the locking members not locking position, and a gripping sleeve connected with the ring and operating simultaneously as an actuating member for unlocking the tool inserted in the tool holder.

Abstract: The present invention relates to a printed circuit board presser device in a drilling machine. The board presser device is arranged such that it includes an axially movable upper-plate presser device which is provided on the outer side of a contact surface of the board presser device with a printed circuit board so that a top end surface of the upper-plate presser device extends to the side of a table beyond the contact surface; and an urging device for pushing the upper-plate presser device against the table by a force larger than an attraction force generated from the board presser device. With such construction, an upper plate is suppressed from floating during drilling the printed circuit board, and a distance of useless transfer movement of a drill decreased, to thereby improve an efficiency of a drilling operation.

Abstract: A cutter insert for a ball end mill is disclosed which includes a plate-like insert body having a front face and a side face extending from the front face. The front face has a generally convexly curved marginal ridge defined by the intersection of the front face with the side face. The marginal ridge serves as a cutting edge. The front face serves as a rake surface for the cutting edge while the side face serves as a relief surface for the cutting edge. The cutting edge has a leading portion to be indexed in the end cutting position and a trailing portion to be indexed in the peripheral cutting position. A land is formed on the rake surface so as to extend along the cutting edge. The land has a width gradually increasing in a direction from the leading portion of the cutting edge toward the trailing portion thereof.