The invention relates to a method and device for making a T-branch for a pipe by joining the shaped end of the branch pipe with internal welding to the ed-ges of a hole in the main pipe. The hole in the main pipe (T) and the arcs corresponding to the main pipe at the end of the branch pipe (P) are mechanically cut by removing one solid part from the hole and two (22) solid parts from the end of the branch pipe in a dry mechanical process, in which the cleanliness of the joint areas remains weldable. The shaped end of the branch pipe (P) is placed around the hole in the main pipe (T) and the joint seam between the pipes is welded by internal welding without a welding additive. A branch hole suitable for this is made by punching perpendicularly against the central axis of the main piped so that punch (1) pushes the piece that detaches from the main pipe into the punch hole (10) of the inner support (9).