Detached and combined type beam compass for lofting

The utility model relates to a detached and combined type beam compass for lofting. The beam compass comprises a front end rod, a middle rod and a rear end rod, wherein the front end rod is connected with the middle rod through a first connecting piece, the other end of the middle rod is connected with the rear end rod through a second connecting piece, a movable sleeve is arranged on the front end rod, and a marking pin is arranged at the lower end of the movable sleeve which is matched with the front end rod through a fastening piece I; and a fixed sleeve is arranged on the rear end rod, a fixed pin is arranged at the lower end of the fixed sleeve which is matched with the rear end rod through a fastening piece II. The diameter of the beam compass can be adjusted according to size requirements of castings, and the beam compass is simple in structure and convenient to use, and has quite high popularization value.