Types stocked: 1 (carbon) · 3 (weathering)
Scope
ASTM F436 / F436M covers hardened steel washers intended for use with high-strength structural fasteners. These are the circular and slotted load-distribution washers required under the head and/or nut of F3125 bolts in properly-designed structural connections.
F436 washers are not general-purpose flat washers. They are heat-treated to prevent embedment into the mating structural steel at the high contact pressures developed by tensioned high-strength bolts. For general load-distribution use at lower stress, specify F844 instead.
Types
| Type | Material | Typical pairing |
|---|---|---|
| 1 | Carbon steel, Q&T | F3125 A325 Type 1, A490 Type 1, general structural |
| 3 | Weathering steel, Q&T | F3125 A325 Type 3, A490 Type 3; exposed-atmospheric construction |
Type 2 was removed from the standard previously.
Mechanical requirements
- Hardness: 38 HRC min, 45 HRC max (Rockwell C) for both Type 1 and Type 3
- Hardness testing: Full surface hardness is specified; decarburization limits apply
- Dimensional tolerance: Tight control on ID, OD, and thickness to ensure correct fit under heavy hex bolt heads and nuts
Configurations
- Circular (round) — the default F436 washer
- Circular, beveled (1:6 taper) — for use on sloped flanges of structural shapes where the bolt axis is not perpendicular to the bearing surface; beveled washers compensate for flange taper on S-shapes and C-channels
- Clipped (truncated) — one edge flattened to clear an adjacent fillet weld or beam flange
All three configurations are covered under F436.
Typical dimensions
For structural bolt sizes, F436 washers are thicker than standard F844 flat washers:
| Bolt size | Nominal OD | Nominal ID | Nominal thickness |
|---|---|---|---|
| 1/2" | 1-1/16" | 17/32" | 0.122"–0.177" |
| 5/8" | 1-5/16" | 11/16" | 0.122"–0.177" |
| 3/4" | 1-15/32" | 13/16" | 0.122"–0.177" |
| 7/8" | 1-3/4" | 15/16" | 0.136"–0.177" |
| 1" | 2" | 1-1/16" | 0.136"–0.177" |
| 1-1/8" | 2-1/4" | 1-1/4" | 0.136"–0.177" |
| 1-1/4" | 2-1/2" | 1-3/8" | 0.136"–0.177" |
| 1-3/8" | 2-3/4" | 1-1/2" | 0.136"–0.177" |
| 1-1/2" | 3" | 1-5/8" | 0.136"–0.177" |
When F436 is required
Per AISC and RCSC specifications, F436 washers are required under the element being turned (typically the nut) during installation, plus additional placements depending on installation method and hole geometry:
- Turn-of-nut with standard holes — washer under the turned element only
- Calibrated wrench tensioning — washer under the turned element only
- Twist-off (F1852, F2280) — no additional washer required at the splined end; washer under nut
- Oversized or slotted holes — F436 washer required at both ends of the bolt, or a plate washer over the slot per AISC
For F959 direct tension indicators, the DTI is placed under the bolt head and an F436 washer goes between the DTI and the turned element.
Coatings
- Hot-dip galvanized per F2329 — standard for A325 Type 1 exterior service
- Mechanical galvanized per B695 — alternative
- Zinc plated per F1941 — interior or controlled environments
- Plain — standard for interior protected applications and for Type 3 weathering
- Zinc-flake coatings (F3019, F1136, F2833) — paired with coated F3125 A490 assemblies
Type 3 weathering washers
Type 3 F436 washers are specified with Type 3 F3125 bolts (A325 or A490) in weathering-steel construction. The weathering chemistry provides atmospheric corrosion resistance matching the structural members (A588, A709 Grade 50W, etc.) and develops the characteristic dark oxide patina with similar timing to the surrounding steel.
Marking
F436 washers do not carry individual grade markings. The supplier's mill certificate identifies type, hardness test results, and batch traceability to the heat lot.
Applications
- F3125 structural bolted connections (the primary use case)
- F1554 Grade 105 anchor bolt terminations where hardened washers are called out
- A354 BD connections
- Any high-strength bolted joint where embedment of a non-hardened washer into the mating steel would cause pretension loss
What F436 is NOT for
- General mechanical assembly at low to moderate load — use F844 instead
- Direct tension indicating — use F959 (compressible DTI washer)
- Locking applications — F436 is a flat washer; for locking, specify split lockwashers, wedge-lock, or Nord-Lock per application requirements
Related specifications
- F3125 — Structural bolts (primary pairing)
- F1554 Grade 105 — High-strength anchor bolts
- F844 — Plain (unhardened) flat washers
- F959 — Direct tension indicators
- F2329 — HDG coating standard
- RCSC Specification — Installation and placement requirements for structural washers
Documentation
California Fastener F436 orders ship with mill certificates showing type, hardness test results, heat number, and coating thickness reports.