OSG 28392TN 7/8-14 NF H4 3-Flute TiN Plug Tap Hy-Pro
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The OSG 28392TN is a new 7/8-14 UNF (fine thread) H4 tolerance plug tap from OSG's Hy-Pro series, manufactured from high-speed steel (HSS-E) and finished with a TiN (Titanium Nitride) coating visible as the gold finish on the threaded portion of the tool. The H4 pitch diameter limit designates a tolerance range of +0.0015" to +0.0020" over basic pitch diameter, producing threads suitable for 3B class fits with standard tolerances. The 3-flute (3S/P) straight-flute design and plug chamfer (3–5 leading threads) make this tap well-suited for through-hole and moderately deep blind-hole applications in steel, cast iron, and aluminum. OSG's Hy-Pro geometry features a modified high-helix relief and precision-ground threads for consistent chip formation and reduced torque in production tapping operations. The square drive shank is compatible with standard tap holders, chucks, and tapping attachments accepting 7/8" diameter shank tooling.
Product Specifications
| Brand | OSG |
| Part Number | 28392TN |
| Thread Size | 7/8-14 |
| Thread Standard | UNF (Unified National Fine) |
| Threads Per Inch | 14 TPI |
| Tap Style | Plug (3–5 thread chamfer) |
| Number of Flutes | 3 |
| Pitch Diameter Limit | H4 |
| Thread Class | 3B |
| Material | High-Speed Steel (HSS-E) |
| Coating | TiN (Titanium Nitride) |
| Series | Hy-Pro |
| Flute Type | Straight Flute |
| Drive Type | Square Shank |
| Condition | New |