Clamp

The utility model discloses a clamp which is used for coordinately machining hollow rods. The clamp comprises main support, a mandrel, an adjusting ring and a dial indicator. The main support comprises a middle support, a left stop block and a right stop block, wherein the left stop block and the right stop block are disposed at the ends of the middle support, and tips are disposed on the two stop blocks respectively. The dial indicator, the adjusting ring and the fixing clamp are disposed on the middle support. The diameter of the mandrel is matched with the aperture of an inner hole of a hollow rod. The mandrel penetrates through the adjusting ring. Tip holes matched with the tips are arranged at two ends of the mandrel. Adjusting screws are disposed along the circumference of the adjusting ring at intervals of every other 90 degrees. The dial indicator is disposed on the adjusting ring. By the clamp, location degree requirements of excircles at two ends of the rod and an middle inner hole of the rod can be