These are the basic parts for the tapping fixture. As you can see most of the parts are 1/2 inch galvanized pipe. The tube is used for the tap handle extension, and was a piece of 3/4 inch O.D. stainless that I had in my scrap box. I'm sure a piece of thick wall conduit would work just as well. I suggest that you assemble the galvanized pipe at the hardware store so you can check it for squareness. The length of the pipe nipples are not critical, you can make this any size that suits you. I have been considering building one of these half size out of 1/4 pipe for use with a smaller tap handle although I have used this one with a #2-56 tap with no problems.
Parts list.
1/2 inch pipe floor flange
1/2 inch pipe nipple, 6 inches long
1/2 inch pipe nipple, 12 inches long
1/2 inch pipe tee
1/2 inch pipe 90 degree elbow
3/4 inch O.D. conduit or tube of choice, 12 inches long
Tap handle