1. Shaft: 3/8'. Capacity: 5/32' to 41/4' inner diameter or 0 to 41/4' outer diameter. Speed: Spindle rotates at 100 RPM. It is not recommended to exceed this speed. This is a professional indicator for locating the center of a workpiece on a drilling or milling machine (alignment) and the median side diameter. 2. The center dial indicator is a measuring tool that uses a lever to transfer the relative position from the workpiece's center to the display, converting it into the angular displacement of the pointer. It is an accurate, practical, and visible tool for finding the relative center of a machined part, such as the circumference and inner hole of the workpiece. 3. Supported measuring range: 00.15', resolution: 0.0005'. This COAX coaxial centering indicator can quickly and precisely set the center for drilling and milling on horizontal or vertical machines. When the stylus rotates, the dial faces the operator, enabling centering. 4. Operation from horizontal to vertical machines and from inner to outer diameters is possible by simply replacing the inductor without modification. When the machine spindle rotates, the indicator remains steady in any desired position, allowing the operator to use both hands for precise table positioning.