American Pipe Threads
Pipe Threads (PTF) are larger in diameter than most UNF or SAE-LT threads and also provide additional strength. PTF threads have a taper like SAE-LT threads to provide a leakproof installation. These threads are designated by nominal pipe diameter.
The 1/8 PTF thread is about 3/8" diameter, and the 1/4 PTF thread is about 1/2" in diameter. A tapped hole is required for installation. PTF fittings are used most often in construction and in the agricultural industry where heavy machinery is required.
Maximum Pressure is 8,000 PSI. All zinc dichromate fittings minimum 72 hours to red rust. All zinc fittings case hardened to Vickers HV1 or 83 min Rockwell 15N. All stainless steel fittings are type 303 stainless.