Abstract: A clamping device for controlling rotation of a chair about a support shaft of a base frame and the chair associated thereto. The clamping device includes a mounting block, clamping components, and calibrating components. The mounting block is securely affixed to a bottom portion of the chair and has first and second channels transversely connected to one another inside the mounting block. The mounting block is pivotably mountable onto a portion of the support shaft and is allowed to rotate thereabout. This portion is insertable into the first channel of the mounting block. The clamping components are mounted into the second channel of the mounting block and are operatively connected to the support shaft for clamping the same. The calibrating components are operatively connected to the clamping components for adjusting the extent with which the clamping components clamp the support shaft. The present clamping device provides a wide range of adjustable positions without any backlash.