Method of making blind tapped holes in connecting flanges of heat exchangers

摘要

A method of making blind tapped holes in heat-exchanger connecting flanges is proposed in which a blind hole is drilled with a drilling tool and a thread is cut with a tap. Before the thread is cut, the hole to be drilled is drilled to the desired length and as deep as possible, and while producing a plane drill-hole bottom in the process, with a drilling tool which has an at least approximately plane end face and thus a point angle of roughly between 150@ and 180@, and after this the thread is then cut in the drill hole with a tap which has a plane end face and having a chamfer which leads from there to the cutting thread and comes to about 1 1/2 thread turns. Thus tapped holes of the greatest possible depth can be made in the flange at a small flange cross-section.