Hose Routing Dos and Don'ts
Nominal Bore Hose follows the SAE 100R14 tubing standard which is typically labeled in 'dash' sizes (1/15 of an inch). For example, 1/2" tubing is 1/2" O.D. with a slightly smaller I.D. Thus, dash 8 (-08) nominal hose is 8/16" or 1/2" O.D., yielding an average I.D. of 13/32". All manufacturers of Nominal Fluoropolymer hose follow the same nominal I.D./O.D. standard.
True Bore Hose on the other hand follows the same I.D. as schedule 40 pipe; therefore, a typical 2" I.D. true bore hose is the exact same bore size as its mating 2" pipe.