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Threads & connections · Pneumatic glossary

Rc — Tapered internal pipe thread

Tapered internal pipe thread

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Term
Rc
Full form
Tapered internal pipe thread
Selection effect
Verify pairing and sealing practice rather than relying on nominal size.

01

Rc: definition and engineering context

Tapered internal pipe thread. BSP-family tapered female thread designation.

The term belongs to the threads & connections context. Its exact limits can depend on the cited standard, catalog convention, unit system, reference state, and component configuration.

02

Why Rc affects pneumatic selection

Verify pairing and sealing practice rather than relying on nominal size.

  • Tube OD: Metric and inch tube sizes are not interchangeable even when close.
  • Push-in fitting: Match tube material, OD, pressure, temperature, and release clearance.
  • NPT: Do not mate it with BSPT solely because nominal sizes appear similar.
  • BSPP / G: Sealing normally occurs with an O-ring, washer, or bonded seal, not on the thread flank.

03

How to evaluate Rc in a catalog or replacement project

Read the value together with its unit, test basis, operating pressure, temperature, circuit state, and manufacturer definition.

For replacement work, compare the complete datasheet and drawing. A matching abbreviation or nominal size does not by itself prove functional or dimensional interchangeability.

  • Tube outside diameter: Outside diameter used to size most push-in pneumatic fittings.
  • Push-to-connect fitting: Collet-and-seal tube connection installed by pushing prepared tube into the fitting.
  • National Pipe Taper thread: Tapered inch pipe-thread system widely used in North America.
  • British Standard Pipe Parallel thread: Parallel pipe thread commonly identified by G.

Selection checklist

What to verify before selection

  1. 01

    Verify pairing and sealing practice rather than relying on nominal size.

  2. 02

    Metric and inch tube sizes are not interchangeable even when close.

  3. 03

    Match tube material, OD, pressure, temperature, and release clearance.

  4. 04

    Do not mate it with BSPT solely because nominal sizes appear similar.

Application caution

Common mistakes

  • Treating Rc as a universal definition without checking the manufacturer or standard context
  • Mixing gauge and absolute values, incompatible units, or different reference conditions in one comparison
  • Selecting a component from the term or nominal value alone without checking the complete operating point and drawing

FAQ

Questions engineers often ask

01Terminology checkWhat does Rc mean in pneumatics?

Tapered internal pipe thread. BSP-family tapered female thread designation.

02Terminology checkWhy does Rc matter when selecting a component?

Verify pairing and sealing practice rather than relying on nominal size.

03Terminology checkCan Rc values be compared directly between catalogs?

Only after the unit, reference condition, test method, operating point, and manufacturer definition have been reconciled.

Source notes

Technical references

This lookup table explains practical usage. Definitions, reference conditions, symbols, and abbreviations may differ by standard or manufacturer. Treat the applicable datasheet and standard as authoritative.

  1. ISO 5598:2020

    Provides the international fluid-power vocabulary used to interpret pneumatic terminology.

  2. ASME B1.20.1

    Defines general-purpose inch pipe threads, including NPT thread form and gauging.