These Boring tool devices are used to set boring tool to the exact diameter on boring machines and machine tools with rotation boring tools. Because of their magnetic bases, they can be held directly on boring spindle. The clamps can fit at any desired position whereby any particular bore size can be set on the device. These devices have ON / OFF switches, as per requirements and aid in holding the job on boring spindle. The ‘ V ‘ slot is ground to 5micron accuracy.