The diameter of the male threaded portion of a #8 SAE/ORB (O-Ring Boss) hydraulic fitting, which corresponds to a dash size of -8, is **3/4-16 UNF**. This means the major diameter of the male thread is approximately **0.750 inches** (or 19.05 mm). The thread specification follows the SAE J1926 standard, with 16 threads per inch (TPI).

For precise measurements, you can use a caliper to measure the outside diameter of the male thread, which should be close to 0.750 inches, accounting for minor variations due to manufacturing tolerances. Always confirm with a thread identification chart or gauge for accuracy.[](https://www.qchydraulics.com/sae-thread-orb-fitting-size.html)[](https://affordabletool.com/mb-08-08-1-2-hose-x-8-sae-orb-male-boss-o-ring-hydraulic-hose-fitting/)