Heavy Hex Nuts · ASTM A563 / A563M

ASTM A563 Heavy Hex Nuts

The nut specification for carbon and alloy steel bolting: Grade A for A307, Grade B for cast-iron flanges, C and D for 105 to 120 ksi bolts, and DH and DH3 heat treated for A325, A490, A354 and Grade 8 — with proof stress by grade and style.

Robust fastener with a thicker, wider hexagonal shape for high-stress applications. Manufactured and stocked across ASTM A194 grades from 2H to 8MA, plain or coated.

ASTM A563 covers the nuts that go with carbon and alloy steel bolts. Each grade is matched to a bolt strength by its proof stress: Grade A (90 to 100 ksi) for A307 and Grade 2 bolts; Grade B (105 to 133 ksi) for flanged joints; Grades C and D (130 to 150 ksi) for 120 ksi bolts; Grade DH (150 to 175 ksi, quenched and tempered) for A325, A490, A354 BD and Grade 8; and DH3, the weathering-steel version. Heavy hex nuts carry a higher proof stress than finished hex of the same grade because of their thicker section.

ASTM A563 Heavy Hex Nuts at a glance

Material specificationASTM A563 / A563M

UNS—

Grade A, heavy hex100 ksi proof

Grade B, heavy hex ≤1 in.133 ksi proof

Grade C / C3, heavy hex144 ksi proof

Grade D, heavy hex150 ksi proof

Grade DH / DH3, heavy hex175 ksi proof · 24–38 HRC

Matching boltsA307 · A449 · A325 · A490 · A354

CertificationEN 10204 3.1 material test report with every lot, traceable to the heat

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Mechanical properties

What ASTM A563 must meet.

Proof stress and hardness — ASTM A563 nuts by grade and style (UNC and 8 UN threads)

Grade · style · size	Proof stress, plain (ksi)	Proof stress, zinc coated (ksi)	Hardness, min	Hardness, max
A · hex · ¼–4	90	68	116 HBW / B68	302 HBW / C32
A · heavy hex · ¼–4	100	75	116 HBW / B68	302 HBW / C32
B · heavy hex · ¼–1	133	100	121 HBW / B69	302 HBW / C32
B · heavy hex · 1⅛–1½	116	87	121 HBW / B69	302 HBW / C32
C, C3 · heavy hex · ¼–4	144	144	143 HBW / B78	352 HBW / C38
D · heavy hex · ¼–4	150	150	159 HBW / B84	352 HBW / C38
DH, DH3 · heavy hex · ¼–4	175	150	248 HBW / C24	352 HBW / C38
DH · hex · ¼–4	150	150	248 HBW / C24	352 HBW / C38

Values per ASTM A563/A563M-21 Table 2 (verified against the specification). Confirm the edition called out on your purchase order with our estimating team. Zinc-coated nuts of Grades A, B and DH carry the lower proof stress shown; fine-thread nuts are listed separately in the specification.

Heat treatment

Grades A, B, C and D: not required. Grades DH and DH3: quenched and tempered at 800 °F minimum. Galvanized DH nuts are lubricated after coating; a dye to show the lubricant is an option under Supplementary Requirement S2.

Full A563 nuts data sheet: chemistry, physical properties and standards →

Dimensions & standards