

The Graco 100077 Hex Heavy Jam Nut is a durable OEM lock-nut designed for securing threaded components in Graco high-pressure sprayers and pumps.
Based on Graco parts manuals and exploded views, Graco 100077 appears in the following equipment assemblies:
The Graco 100077 Hex Heavy Jam Nut is a robust, low-profile lock-nut used to secure threaded components in high-pressure pump and fluid-handling assemblies. Its jam-nut profile helps prevent loosening under vibration and pressure cycling.
| Part Number | 100077 |
|---|---|
| Type | Hex Heavy Jam Nut (lock-nut style, low-profile) |
| Thread | 5/16-18 UNC (as referenced in Graco parts listings for certain assemblies) |
| Typical Use | Securing priming/valve rods, brackets, and sub-assemblies in airless pumps, proportioners, line drivers, and dispense valves. |
| Finish/Material | Heavy-duty steel nut (finish may vary by kit/build; verify per model BOM) |