PartsTable TECHNICAL DATA SHEET
JULY 2026Technical Data Sheet

620-608Seat,valve

Steward Machine Co Inc · NSN 4820-00-063-8911 · FSC 4820 · No Item Name Available
Verified by PartsTable
NSN 4820-00-063-8911 — this item is cataloged by the U.S. Government under National Stock Number 4820-00-063-8911. Primary manufacturer part number: 620-608.
Features
  • Seat,valve — FSC 4820
  • Under Flange Height: 0.188 INCHES NOMINAL IN
  • Seat Angle in Deg: 30.000 NOMINAL
  • Material: COBALT ALLOY FACE
  • Seating Surface Shape: ANGULAR
  • Body Inside Diameter: 1.290 INCHES MINIMUM AND 1.292 INCHES MAXIMUM IN
  • Hardness Rating: 202.0 BRINELL STANDARD NOMINAL BODY
  • Material: STEEL COMP 410 BODY
Applications
  • Flow control in piping systems
  • Pressure regulation
  • Steam and fluid isolation
  • Applications requiring Cobalt Alloy Face construction
General Description

The Seat,valve, cataloged under National Stock Number 4820-00-063-8911, is classified within Federal Supply Class 4820 (No Item Name Available) of the Valves group. The primary manufacturer of record is Steward Machine Co Inc. Government technical data includes 12 verified specifications, sourced from the Federal Logistics Information System (FLIS). This item has 3 commercial cross-references from 2 manufacturers, enabling identification through both NSN and commercial part number lookups. 2 verified substitutes exist in the FLIS interchangeability database. Current acquisition status: Active.

Technical Specifications
ParameterValue
NSN4820-00-063-8911
Primary Part Number620-608
Item NameSeat,valve
FSC / FSG4820 / 48 — No Item Name Available
ManufacturerSteward Machine Co Inc
StatusACTIVE
Under Flange Height0.188 INCHES NOMINAL IN
Seat Angle in Deg30.000 NOMINAL
MaterialCOBALT ALLOY FACE
Seating Surface ShapeANGULAR
Body Inside Diameter1.290 INCHES MINIMUM AND 1.292 INCHES MAXIMUM IN
Hardness Rating202.0 BRINELL STANDARD NOMINAL BODY
MaterialSTEEL COMP 410 BODY
Style DesignatorPLAIN FLANGED
Hardness Rating202.0 BRINELL STANDARD NOMINAL FACE
Body Outside Diameter2.315 INCHES MINIMUM AND 2.320 INCHES MAXIMUM IN
Flange Seat to Disk End Height0.750 INCHES NOMINAL IN
Flange Diameter2.805 INCHES MINIMUM AND 2.810 INCHES MAXIMUM IN
Lifecycle & Compliance
Acquisition StatusACTIVE
HAZMATNo
Verified Substitutes 2
3020-00-251-0865 INTERCHANGEABLE
Gear,helical
2990-01-261-5430620608 INTERCHANGEABLE
Cap Assembly,protective,muffler-
Trw Inc Trw Intl Trade Government Sales Dept
Cross-Reference Index
Part NumberManufacturer
620-608 PRIMARY Steward Machine Co Inc (USA)
620-608 Hardie-Tynes Co., Inc. (USA)
60-620PC608 Hardie-Tynes Co., Inc. (USA)
Related Parts
3020-00-251-0865INTERCHANGEABLE
GEAR,HELICAL
2990-01-261-5430INTERCHANGEABLE
CAP ASSEMBLY,PROTECTIVE,MUFFLER-
620608

Frequently Asked Questions

What is NSN 4820-00-063-8911?

NSN 4820-00-063-8911 is a Seat,valve, manufactured by Steward Machine Co Inc, classified under FSC 4820 (No Item Name Available). Status: active.

What are the part numbers for NSN 4820-00-063-8911?

NSN 4820-00-063-8911 has 3 cross-referenced part numbers: 620-608 (Steward Machine Co Inc), 620-608 (Hardie-Tynes Co., Inc.), 60-620PC608 (Hardie-Tynes Co., Inc.).

What NSN replaces 4820-00-063-8911?

There are 2 known substitutes for 4820-00-063-8911: 3020-00-251-0865, 2990-01-261-5430. Verify interchangeability with system specifications before substitution.

What are the specifications of 620-608?

Key specifications for 620-608: Under Flange Height: 0.188 INCHES NOMINAL IN; Seat Angle in Deg: 30.000 NOMINAL; Material: COBALT ALLOY FACE; Seating Surface Shape: ANGULAR. 12 total characteristics are documented in the Federal Logistics Information System.

Validated with multiple authoritative sources, including Government, OEM, and Certified sources.
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