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ASTM F436M — Metric Hardened Steel Washers
ASTM F436M is the metric-series companion specification to F436. It covers hardened steel washers for fasteners with nominal thread diameters from M12 through M100. The mechanical, hardness, and chemical requirements are identical to F436 inch-series washers; only the dimensional tables differ to match metric thread sizes. Both Type 1 carbon steel and Type 3 weathering steel grades are available in metric.
F436 vs F436M Difference
F436 is the inch-series specification (1/4 in. through 4 in. nominal thread diameter). F436M is the metric-series companion (M12 through M100). Hardness, mechanical, marking and chemical-composition clauses are shared; the dimensional tolerance and per-size tables are sized to inch or metric thread series. A washer stamped to F436M meets the same HRC 38–45 through-hardened hardness as an F436 washer of equivalent grade.
F436M Mechanical Properties
F436M through-hardened metric washers shall have a hardness of 38 to 45 HRC, except when zinc-coated by the hot-dip process, in which case they shall have a hardness of 26 to 45 HRC. Carburized washers shall be carburized to a minimum depth of 0.38 mm (the metric-series value; the inch-series equivalent is 0.015 in.) and shall have a surface hardness of 69 to 73 HRA or 79 to 83 HR15N. Hot-dip galvanized carburized washers must meet 63 to 73 HRA or 73 to 83 HR15N. Carburized cores must reach a minimum 30 HRC or 65 HRA. Metric washers through M36 are through-hardened; washers over M36 may be either through-hardened or carburized.
F436M Dimensional Tolerances (Metric Washers)
| Dimensional Characteristics | 12mm through 16 mm Nominal Size |
>16 mm Nominal Size |
|---|---|---|
| Flatness: max deviation from straightedge placed on cut side shall not exceed | B | B |
| Concentricity, mm: center of hole to outside diameter | 0.6 mm FIRA | 0.9 mm FIRA |
| Burr shall not project above immediately adjacent washer surface more than (mm) | 0.25 mm | 0.25 mm |
|
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Common F436M Metric Sizes
F436M metric washers are supplied in standard fastener thread sizes M12, M14, M16, M20, M22, M24, M27, M30, M36, M42, M48, M56, M64, M72, M80, M90 and M100. Per-geometry inside diameter, side dimension and thickness data for metric Type 1 are published on the circular and beveled variant pages.
F436M Chemistry — Same as F436
Chemistry requirements for F436M are identical to F436. Type 1 limits P max heat analysis 0.040 / product analysis 0.050; S max heat 0.050 / product 0.060. Type 3 weathering steel requires Cu 0.25–0.45, Ni 0.25–0.45, Cr 0.45–0.65, Si 0.15–0.35 (heat analysis) plus a Corrosion Resistance Index of 6.0 or higher per ASTM G101. Full chemistry tables: F436 washer specifications.
Companion Metric Fastener Standards
F436M metric washers are typically supplied with: F3125/F3125M heavy hex structural bolts (Grades A325M, A490M), A563M heavy hex nuts, and F959M direct-tension-indicator (DTI) squirter washers where joint tension verification is required.
Frequently asked questions
What is the difference between ASTM F436 and F436M?
F436 and F436M are the same standard with two dimension systems. F436 covers inch washers from 1/4 in. through 4 in. nominal bolt size; F436M covers metric washers from M12 through M100. Chemistry, mechanical and corrosion requirements are identical between F436 and F436M — the only difference is the dimensional table and tolerance system. Both Types (1 carbon steel and 3 weathering steel) and all four styles (circular, beveled, clipped, extra thick) exist in both inch and metric versions.
What are the F436M metric size ranges?
F436M Table 4 covers metric circular washers from M12 through M100. The standard thickness band scales with bolt diameter: nominal 3 mm at M12 through M22, 4 mm at M24 through M36, 5 mm at M42 through M64, and 6 mm at M72 through M100. Extra-thick variants run nominal 8 mm in 1/2 in. through 4 in. equivalent metric sizes for structural oversized-hole applications.
Are F436M washers used with metric structural bolts?
Yes. F436M washers pair with ASTM F3125 Grade A325M / A490M structural metric bolts (the metric equivalents of A325 / A490) for high-strength structural connections. The matching nut standard is ASTM A563M. F436M is also referenced in ISO 7415 (high-strength structural joints, HSFG) and in EN 14399-6 (structural bolting flat washers) for cross-system compatibility on global EPC projects.
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