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Rigid conduit thread is an NPT straight thread. The threads cut on galvanized and black iron and copper require a leak resistant joining, those on conduit do not. If 3/4" electrical fittings are what you are trying to accomplish, I would suppose that a 3/4" hand die for water/gas line would suffice though it would be unnecessary as conduit threaders are cheaper and I am not sure if the fine/coarseness of the threads will match up with pre-threaded electrical fittings.
The two most prevalent threads that are cut are NPT and NPSM. NPT (National Pipe Taper) is used to join pipe in which a seal is desired. NPSM (National Pipe Straight Mechanical) is a straight or parallel thread. This thread is traditionally used to join heavy wall conduit together. As far as which one to use, be sure to check the code in your area to ensure that you are using the correct thread. Actually both of these threads maintain the same thread pitch, so they will screw together just remember that a NPT and an NPSM thread will not seal.