Yes, Sch 40 stainless steel pipe can be threaded. Threading involves cutting threads into the end of the pipe so that it can be screwed into fittings or other pipes. Stainless steel is a material commonly used for pipes due to its corrosion resistance and durability, and Sch 40 refers to the thickness of the pipe wall according to the Schedule system.

Threading stainless steel pipe schedule 40 requires specialized tools and techniques to ensure the threads are cut cleanly and accurately without damaging the pipe. It's often done using a threading machine or a handheld pipe threading tool.

However, it's important to note that not all stainless steel pipes are threaded. Depending on the application and requirements, pipes may be joined using other methods such as welding, compression fittings, or flanges. Threading is typically used for pipes that need to be easily connected and disconnected or for installations where welding is not feasible or desired.