ASME B2.1-1968 PDF

Full title and description

St ASME B2.1-1968 — Pipe Threads (Except Dryseal). This American national standard (issued as USAS/ANSI B2.1 in 1968) specifies thread forms, designations, dimensions, tolerances and gaging practice for common inch pipe threads (NPT, NPS and related forms) except dryseal (self-sealing) types.

Abstract

The B2.1-1968 standard defines the USA standard pipe thread form and gives the graphic and dimensional data, designations (NPT, NPS, etc.), recommended gaging points and manufacturing/gaging notes for general-purpose pipe threads. Dryseal (NPTF) and special fuel/oil instrument threads are excluded and handled in companion documents. The standard uses inch units and assumes right‑hand threads unless otherwise noted.

General information

• Status: Cancelled / superseded (historical standard).
• Publication date: January 1, 1968.
• Publisher: Issued under USAS/ANSI designation (commonly referenced as ASME/ANSI in later revisions).
• ICS / categories: Special screw threads / pipe and screw threads (commonly aligned with ICS 21.040.30 class for special screw threads).
• Edition / version: 1968 edition (original).
• Number of pages: Approx. 50 pages (sources report ~50–51 pages).

Scope

This standard covers the dimensional specifications, thread forms and gaging references for a range of USA pipe threads used for general‑purpose piping, fittings and valves (tapered external threads and corresponding internal threads, plus straight/coupling forms where applicable). It explicitly excludes dryseal (self‑sealing/NPTF) thread types, which are covered in the companion B2.2 (later redesignated standards). All nominal dimensions are given in inches.

Key topics and requirements

• Designation system and nomenclature for USA pipe threads (NPT, NPS, NPSC, NPSM, etc.).
• Thread profile and geometry (60° thread angle; truncated crest/root and basic height formulas used for manufacture and gaging).
• Dimensional tables for nominal sizes, pitches (threads per inch), major/minor/pitch diameters and limits.
• Gaging points and references for limit and working gauges used to verify conformity.
• Exclusions and cross‑references (dryseal/NPTF threads treated in separate standard).
• Notes on handedness (right‑hand unless specified) and manufacturing/inspection guidance for avoiding leakage and galling.

Typical use and users

Used historically by piping and fitting manufacturers, valve makers, plumbing and HVAC equipment designers, inspection and metrology labs, gauge manufacturers and procurement/specification engineers who needed standard dimensions and gaging practices for inch‑based pipe threads. Today it is primarily of interest for legacy drawings, historical reference and for understanding the lineage of current ASME/ANSI pipe‑thread standards.

Related standards

Key related and successor standards include USAS/ANSI B2.2 (Dryseal Pipe Threads — 1968), and the later revision/redesignation ASME/ANSI B1.20.1 (Pipe Threads, General Purpose, Inch — 1983 and subsequent editions). Other related documents include ASME B1.20.3 (NPTF / Dryseal) and international standards such as ISO/EN pipe‑thread documents (e.g., ISO 7‑1 / EN 10226).

Keywords

B2.1-1968, Pipe threads, NPT, NPS, USAS B2.1, ANSI B2.1, thread gaging, tapered threads, pipe fittings, NPTF (dryseal), ASME B1.20.1 (successor).

FAQ

Q: What is this standard?

A: St ASME B2.1-1968 (issued as USAS/ANSI B2.1 in 1968) is the historical American standard that defined pipe thread forms, designations and dimensional/gaging data for general‑purpose inch pipe threads (excluding dryseal types).

Q: What does it cover?

A: It provides thread profiles, designation rules (NPT/NPS etc.), dimensional tables (major/minor/pitch diameters, threads per inch), tolerances and recommended gaging practices for general‑purpose pipe threads; dryseal (self‑sealing) threads are excluded and handled elsewhere.

Q: Who typically uses it?

A: Historically, manufacturers of pipe fittings, valves and gauges, inspection/metrology labs, designers and specifiers in piping/plumbing industries; today it is mainly referenced for legacy documentation and to trace requirements adopted into later ASME/ANSI standards.

Q: Is it current or superseded?

A: It has been cancelled/superseded — the content of ANSI/USAS B2.1‑1968 was revised and redesignated under ASME/ANSI B1.20.1 (Pipe Threads, General Purpose, Inch) in later revisions (notably the 1983 redesignation and subsequent ASME B1.20.1 editions). Consult the active ASME B1.20.1 edition for current requirements.

Q: Is it part of a series?

A: Yes — it originally formed part of the family of US pipe‑thread standards (B2 committee documents) together with B2.2 (dryseal) and related gaging and instrument thread subdocuments; the family was later reorganized under the ASME/ANSI B1.20.x series.

Q: What are the key keywords?

A: NPT, NPS, pipe threads, tapered threads, thread gaging, USAS B2.1, ANSI B2.1, ASME B1.20.1, dryseal (excluded), inch threads.