Attaching an air compressor to your new compressed air system can be done many different ways. How you do this depends on what compressor you are using. We have had luck cutting and tapping the metal lines of all three of these A/C compressors. We have used both 1⁄8-inch, 27 tpi NPT and 1⁄4-inch, 18 tpi NPT taps to cut threads in the aluminum outlet lines of York and Harrison R4 compressors. Then you can use brass NPT fittings to attach various lines, switches, one-way valves, and so on. You also can have custom hoses made, as we did .