16 circular tube can be drilled with 9 diameters?

16 circular tube can be drilled with 9 diameters. It is relatively simple to punch holes with a circular pipe punch. Sometimes, in order to improve work efficiency, a circular pipe puncher is often used to punch multiple holes at a time, sometimes as many as 30 holes, which can improve efficiency. When the mandrel hole is put into the pipe, the alignment between the mandrel hole and the punching needle may not be so accurate and straight, otherwise the pipe will roll when punching, and the punching will easily damage the tool mandrel and cause the mandrel to be lost.