API Spec 5B-2017 (2021) PDF

Full title and description

API SPEC 5B — Threading, Gauging, and Inspection of Casing, Tubing, and Line Pipe Threads. Sixteenth Edition (December 1, 2017) issued by the American Petroleum Institute, published with subsequent errata and addenda through Addendum 3 (January 2021). The specification defines thread forms, dimensions, tolerances, marking, and the gauges and inspection methods used to verify compliance for casing, tubing and line pipe threads.

Abstract

This specification provides detailed dimensional requirements, tolerance limits, and gauging/inspection procedures for API thread forms used on casing, tubing and line pipe. It covers functional gauges (ring and plug), individual element measurement instruments, measurement of thread features (standoff, diameter, ovality, addendum, taper, lead, height and angle), and rules for acceptance and rejection of threaded connections. The 16th edition (2017) has been published with errata and addenda through 2021 to maintain alignment with the API Monogram program and field practice.

General information

• Status: Current (16th edition with addenda through 2021; verify API for any later revisions as needed).
• Publication date: 1 December 2017 (Sixteenth Edition); Addendum 3 issued January 2021 (monogram effective date noted in addendum).
• Publisher: American Petroleum Institute (API).
• ICS / categories: Petroleum and natural gas industries — casing, tubing and drill pipe (commonly indexed under ICS 75.180.10).
• Edition / version: 16th edition (2017) with Errata 1 & 2 and Addenda 1–3 (latest addendum January 2021).
• Number of pages: 115 pages (PDF/print product length).

Scope

Specifies thread types, dimensional limits, tolerances, gauging practices, and inspection techniques for API-standard threads used on casing, tubing, and line pipe. Applies to manufacture-stage inspection, intermediate inspections, delivery inspections, and purchaser/manufacturer acceptance testing. It includes requirements for functional gauges, individual-element measuring instruments, and procedures for determining conformance of threads that have 11½ turns per inch or fewer (0.45 turns per mm) and other typical thread forms used in the oil and gas industry.

Key topics and requirements

• Definitions of API thread forms for casing, tubing and line pipe (round, buttress, extreme-line and common proprietary forms).
• Dimensional drawings and tolerances for thread elements (pitch diameter, addendum, height, taper, lead, angle, etc.).
• Specification and use of ring, plug and working/reference master gauges including certification requirements.
• Inspection methods and instruments for individual thread element measurement and functional gauging.
• Acceptance and rejection criteria, marking and record-keeping for gauging results.
• Guidance on gauge certification traceability and the API Monogram program effective dates as referenced in the addenda.

Typical use and users

Used by pipe and connection manufacturers, quality and inspection personnel, third-party inspectors, gauge manufacturers and calibration laboratories, drilling and completion contractors, and purchasers specifying thread acceptance criteria. It is a reference for gauge makers producing API ring/plug/working gauges and for organizations participating in the API Monogram and gauge certification programs.

Related standards

Closely related API publications include API RP 5B1 (Gauging and Inspection of Casing, Tubing and Line Pipe Threads) and the family of API casing/tubing/line-pipe specifications such as API Spec 5CT and API Spec 5L; ISO documents historically referenced include ISO 10422 (which adopted earlier editions of API STD 5B) and other ISO/API interfaces for pipe and thread standards. Users should consult API RP 5B1 for gauging practice details and API Spec 5CT/5L for the product requirements that use API 5B thread definitions.

Keywords

API SPEC 5B, threads, gauging, ring gauge, plug gauge, casing threads, tubing threads, line pipe threads, thread inspection, API Monogram, addendum 2021, standoff, pitch diameter, ovality, addendum, taper, lead.

FAQ

Q: What is this standard?

A: API SPEC 5B is the American Petroleum Institute specification that sets the dimensional, tolerance, gauging and inspection requirements for casing, tubing and line pipe threads used in oil and gas operations (16th edition, 2017, with addenda through January 2021).

Q: What does it cover?

A: It covers thread forms and dimensions, tolerances, the design and use of functional gauges (ring and plug), instruments for measuring individual thread elements, inspection procedures, and acceptance/rejection criteria for threaded connections.

Q: Who typically uses it?

A: Manufacturers of casing/tubing/line pipe, gauge makers and calibration labs, inspection and quality personnel, purchasers specifying threaded connections, drilling/completion contractors, and organizations participating in API Monogram/gauge certification programs.

Q: Is it current or superseded?

A: As of February 19, 2026, the authoritative published edition remains the Sixteenth Edition (December 1, 2017) with errata and addenda through Addendum 3 (January 2021). No later 5B edition was found in public API listings during this check, but users should verify the API standards catalog or API Standards Department for the absolute latest status before relying on the standard for compliance.

Q: Is it part of a series?

A: Yes — it is part of the API casing/tubing/line-pipe family of specifications and references related practices (for example API RP 5B1) and other product specs such as API Spec 5CT and API Spec 5L that depend on the thread definitions in 5B.

Q: What are the key keywords?

A: Threading, gauging, inspection, ring gauge, plug gauge, casing, tubing, line pipe, API Monogram, tolerances, standoff, addendum, pitch diameter, ovality.