The Washer,flat, cataloged under National Stock Number 5310-01-031-5018, is classified within Federal Supply Class 5310 (Nuts and Washers) of the Hardware and Abrasives group. The manufacturer of record is Unison Industries Llc. Government technical data includes 7 specifications, cited from the U.S. Government catalog. The record lists 1 manufacturer part number for this item, enabling identification through both NSN and commercial part number lookups. 1 additional reference document (drawings, advisory and superseded references) is recorded in the U.S. Government catalog. 1 item shares a part number with this NSN in the catalog (possible match — not a government interchangeability claim). Current acquisition status: Active.
| Parameter | Value |
|---|---|
| NSN | 5310-01-031-5018 |
| Primary Part Number | 117998 |
| Item Name | Washer,flat |
| FSC / FSG | 5310 / 53 — Nuts and Washers |
| Manufacturer | Unison Industries Llc |
| Status | ACTIVE |
| Width Across Flats | 0.610 INCHES MINIMUM AND 0.630 INCHES MAXIMUM IN |
| Cross-Sectional Shape Style | RECTANGULAR |
| Peripheral Shape Style | SQUARE |
| Hole Width Across Flats | 0.265 INCHES MINIMUM AND 0.270 INCHES MAXIMUM IN |
| Center Hole Shape Style | ROUND W/FLATS |
| Hole Diameter | 0.318 INCHES MINIMUM AND 0.328 INCHES MAXIMUM IN |
| Thickness | 0.008 INCHES MINIMUM AND 0.012 INCHES MAXIMUM IN |
| Acquisition Status | ACTIVE |
| DEMIL Code | DEMIL A — No Demilitarization Required |
| Hazard | No hazard code in the DLA record (HMIC N) |
| Criticality Code | X |
| Part Number | Manufacturer |
|---|---|
| 117998 PRIMARY | Unison Industries Llc (USA) |
| Reference | Meaning |
|---|---|
| 117998 | 5/9 Secondary reference U.S. Government activity |
NSN 5310-01-031-5018 is a Washer,flat, manufactured by Unison Industries Llc, classified under FSC 5310, Nuts and Washers. Status: active.
NSN 5310-01-031-5018 has 1 manufacturer part number on file: 117998 (Unison Industries Llc).
1 possible match (shared part number, not a government interchangeability claim): 5110-01-186-7748. Verify interchangeability with system specifications before substitution.
Key specifications for 117998: Width Across Flats: 0.610 INCHES MINIMUM AND 0.630 INCHES MAXIMUM IN; Cross-Sectional Shape Style: RECTANGULAR; Peripheral Shape Style: SQUARE; Hole Width Across Flats: 0.265 INCHES MINIMUM AND 0.270 INCHES MAXIMUM IN. 7 specifications are documented in the U.S. Government catalog.
No hazard code in the DLA record (HMIC N). Hazard information on this page is shown exactly as it appears in the DLA record.
U.S. Government catalog: edition PUBLOGDVD v12.0.0 (OCT 2026), edition date 2026-10-01, retrieved 2026-10-16.
U.S. Government catalog: edition PUBLOGDVD v12.0.0 (OCT 2026), edition date 2026-10-01, retrieved 2026-10-18.