ASME B18 series from the American Society of Mechanical Engineers defines dimensions and tolerances of inch-series bolts, nuts, screws and washers, typically used together with ASTM material standards in North American and global imperial projects.

ASME to GB & ISO Equivalents

• ASME B18.2.1 ≈ GB/T 5782/5783 (metric equivalent) — Hex bolts
• ASME B18.2.2 ≈ GB/T 6170 — Hex nuts
• ASME B18.22.1 ≈ GB/T 97.1 — Plain washers
• ASME B18.3 ≈ GB/T 70.1 — Socket head cap screws

Popular ASME Standard Numbers

Bolts & Screws

• ASME B18.2.1 — Square and hex bolts and screws (inch)
• ASME B18.2.3.1M — Metric hex cap screws
• ASME B18.2.3.2M — Metric hex bolts
• ASME B18.2.3.5M — Metric heavy hex bolts
• ASME B18.3 — Socket cap, shoulder and set screws (inch)
• ASME B18.3.1M — Metric socket head cap screws
• ASME B18.6.2 — Slotted and recessed head screws
• ASME B18.6.3 — Machine screws and tapping screws (inch)

Nuts

• ASME B18.2.2 — Square and hex nuts (inch)
• ASME B18.2.4.1M — Metric hex nuts
• ASME B18.2.4.2M — Metric hex nuts, style 2
• ASME B18.2.4.6M — Metric heavy hex nuts
• ASME B18.2.4.5M — Metric hex flange nuts
• ASME B18.16 — Prevailing torque locknuts (inch)

Washers

• ASME B18.22.1 — Plain washers (inch)
• ASME B18.21.1 — Lock washers (inch)
• ASME B18.22M — Metric plain washers
• ASME B18.21.2M — Metric lock washers
• ASME B18.8 — Spring pins (inch)

Related Dimensional Standards

• ASME B1.1 — Unified inch screw threads (UNC/UNF)
• ASME B1.13M — Metric screw threads (M profile)
• ASME B18.2.8 — Clearance holes for bolts, screws and studs
• ASME B18.18 — Quality assurance for fasteners
• ASME B18.24 — Part identifying number (PIN) code system for B18 fasteners