NH is a busy little designation. It is used for Fire Hose and Garden Hose.
NH as it is used for Fire Hoes has many sizes as are defined in NFPA
Garden Hose thread has only one base size, but it is called by six different size designations: 1/2"-11-1/2 NH or 5/8"-11-1/2 NH or 3/4"-11-1/2 NH or 1/2"-11-1/2 NHR or 5/8"-11-1/2 NHR or 3/4"-11-1/2 NHR. Let's take the differences and similarities one at a time.
NH or NHR:
Both designations are used for garden hose; the difference is only in how the thread is manufactured. Both will fit on the standard faucet. NH is for standard garden hose coupling threads of full form as produced by cutting or rolling. NHR is for standard garden hose coupling threads where the design utilizes thin walled material which is formed to the desired thread.
They are designated differently because they do have some small differences in the manufactured size, and to best benefit your production of either of these threads it is best that you have the correct designation identified and the correct screw thread gages purchased for the designation required in your application.
1/2" or 5/8" or 3/4"
All three size designations are used for garden hose, the difference is only in how the thread is defined and what it is attached to. All three will fit on the standard faucet. Let me explain. Most screw threads are designated by the nominal major diameter of the screw thread, but this is not true for pipe or hose screw threads. In the case of pipe and hose; screw thread size designations are based on the nominal size of the pipe or hose. The nominal size of the pipe or hose is usually the size of the lumen or hole; the inside diameter, which defines the carrying capacity of the pipe or hose. Garden hose in America comes in three sizes: 1/2" or 5/8" or 3/4", but since the faucet size used for American garden hose connections has only one size, all three sizes are really identical in fit and function.
Original Posting: 4/20/2012
Last Revised: 6/4/2013
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