ASME B1.1 UNC Thread Limiting Dimensions — External 2A / Internal 2B (#1 – 4 in)

Documents

Shipments are backed by Mill Test Certificate (MTC), Dimensional Report, Salt Spray Test Report on request, with full batch traceability from raw material to finished product. Quality management follows the owner-confirmed compliance list: ISO 9001:2015, RoHS, REACH. Exact document sets are confirmed on the order.

Quotation

• The fastener family (ASME B1.1 UNC Thread Limiting Dimensions — External 2A / Internal 2B (#1 – 4 in)) plus the standard designation from your drawing — DIN / ISO / JIS / ASTM / ANSI, or a drawing for custom parts.
• Size (diameter and length), thread type (metric or inch), property class or grade, and coating or finish.
• Quantity per size and your target delivery date.
• Destination country, and any required documents (for example a mill test certificate) so the quote includes them.

Sample & supply

Minimum order quantity is 10,000 pieces. Stock items run 3–7 days. Quantities or variants outside the standard range are confirmed at quotation.

Storage & shipping

Parts are packed for export and shipped factory-direct to buyers in Europe, Asia, the Americas and the Middle East. Store fasteners dry and protected until installation, and keep coated parts in their packaging until use; specific packing and preservation requirements can be stated on the order and confirmed at quotation.

How do I use the 2A/2B limiting dimensions in practice — what do the max/min values mean for inspection and for plating?

Each max/min pair is a gage envelope, not a target. A 2A bolt thread must measure at or under the major max and pitch max and at or above the minimums — in practice, verified with a GO/NOGO thread ring; the internal 2B values are the mirror image checked with a thread plug. The tolerance bands are asymmetric by design: the external thread sits below basic size and the internal above, and the gap between them is the allowance that guarantees a commercial bolt always enters a commercial nut — 2A/2B is the everyday pair of volume assembly. Two places the numbers bite in practice. Plating: coating applied after threading grows every diameter, which is exactly what the 2A allowance budgets for — a heavily plated thread still assembles; but if the part is plated before threading or re-gaged after heavy galvanizing, check against the table rather than assuming fit. Inspection economics: the limits let receiving inspection accept or reject on measurement instead of trial assembly — a bolt that gauges NOGO against the pitch limits is a nonconformance even if it winds in by hand. For 3A/3B tighter classes or UNEF limits beyond these charts, that is a per-RFQ line with the gaging plan named.

What is the MOQ and lead time for threaded parts on this standard?

The minimum order quantity is 10,000 pieces. Stock items ship in 3–7 days; non-stock items are confirmed at quotation. Common thread sizes on this standard are widely stocked; confirm the exact schedule against quantity and size mix at quotation.