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Pipe & Pneumatic Fittings · ASME B1.20.1 · Application guide

What Are NPT Pipe Thread Fittings Used For?

What Are NPT Pipe Thread Fittings Used For? application image

NPT Pipe Thread Fittings are used primarily for joining and sealing fluid or pneumatic lines. This page lists the industries and assemblies where they are specified, the selection criteria that matter for each application, installation practice, and the cases where a different fastener type is the correct choice. Parts are supplied to ASME B1.20.1. Stocked across roughly M1 to M312, they cover general to heavy-duty work.

Typical Applications for NPT Pipe Thread Fittings

The most common settings where these are specified:

  • Pneumatic systems: connecting air lines, cylinders and valves on automation rigs.
  • Hydraulic & fluid power: sealed, pressure-rated joints in fluid lines.
  • Process & plant piping: tapped connections on manifolds and equipment.
  • General machine building: fastening covers, brackets, motors and sub-assemblies on production equipment.
  • Maintenance & repair (MRO): a stocked size for servicing existing plant where the original fastener spec must be matched.

How to Specify NPT Pipe Thread Fittings for Your Application

  • Size: Match the nominal size to the mating thread or hole. This product spans M1–M312; check the full table below for the exact dimensions of each size.
  • Thread & pressure: Match the thread form (BSP/NPT/metric) and pressure rating to the line, and seal appropriately (tape, sealant or O-ring).
  • Environment: For damp, coastal or chemical exposure prefer A4/316 stainless or a suitable coating; indoors, plated steel or A2 is usually sufficient.
  • Standard: This product is supplied to ASME B1.20.1. Quoting the standard on your order guarantees interchangeable dimensions between suppliers.

Installation & Assembly Practice

  • Seal tapered threads with PTFE tape or anaerobic sealant applied clear of the first thread; parallel threads seal on a washer or O-ring, not on the thread.
  • Tighten to the fitting manufacturer's torque — over-tightening tapered threads splits female ports.

Common Selection Mistakes with NPT Pipe Thread Fittings

  • Mating BSP and NPT threads directly — the 55°/60° forms do not seal against each other.
  • Exceeding the pressure rating of the lowest-rated component in the line.

Where NPT Pipe Thread Fittings Are Not the Right Choice

Do not mix thread forms (BSP into NPT) without an adapter, and do not exceed the pressure rating of the lowest-rated component.

Technical Drawing

Customize the parameters below — every spec field is editable, and the drawing redraws to match the values you choose. Changing the size will snap the other fields to that size's standard values; you can then override any individual value.

Sends the selected values to the quote form below.

Request a Quote

Set the size and options in the drawing above, then send the exact configuration straight to this form.

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Specification
Business Information

Dimensions & Specifications (ASME B1.20.1)

SizeNominal size (in)Major diameter (mm)Pitch (mm)Threads per inch (TPI)TaperReference standardNotes
1/16 NPT1/167.9380.941271:16ASME B1.20.1Tapered pipe thread, self-sealing
1/8 NPT1/810.2870.941271:16ASME B1.20.1Tapered pipe thread, self-sealing
1/4 NPT1/413.7161.411181:16ASME B1.20.1Tapered pipe thread, self-sealing
3/8 NPT3/817.1451.411181:16ASME B1.20.1Tapered pipe thread, self-sealing
1/2 NPT1/221.3361.814141:16ASME B1.20.1Tapered pipe thread, self-sealing
3/4 NPT3/426.671.814141:16ASME B1.20.1Tapered pipe thread, self-sealing
1 NPT133.4012.20911.51:16ASME B1.20.1Tapered pipe thread, self-sealing
1-1/4 NPT1-1/442.1642.20911.51:16ASME B1.20.1Tapered pipe thread, self-sealing
1-1/2 NPT1-1/248.262.20911.51:16ASME B1.20.1Tapered pipe thread, self-sealing
2 NPT260.3252.20911.51:16ASME B1.20.1Tapered pipe thread, self-sealing
2-1/2 NPT2-1/273.0253.17581:16ASME B1.20.1Tapered pipe thread, self-sealing
3 NPT388.93.17581:16ASME B1.20.1Tapered pipe thread, self-sealing
3-1/2 NPT3-1/2101.63.17581:16ASME B1.20.1Tapered pipe thread, self-sealing
4 NPT4114.33.17581:16ASME B1.20.1Tapered pipe thread, self-sealing
5 NPT5141.33.17581:16ASME B1.20.1Tapered pipe thread, self-sealing
6 NPT6168.2753.17581:16ASME B1.20.1Tapered pipe thread, self-sealing

Frequently Asked Questions

Can I mix BSP and NPT NPT Pipe Thread Fittings?

Not directly — the thread forms differ in angle and taper. Use a dedicated BSP-to-NPT adapter, and seal with the method suited to the thread (tape, sealant or O-ring).

What material should NPT Pipe Thread Fittings be for outdoor use?

For damp, coastal or chemical environments specify A4 (316) stainless or a suitably coated steel. For indoor or dry use, A2 (304) stainless or zinc-plated steel is normally adequate.

Are NPT Pipe Thread Fittings made to a recognized standard?

Yes — they are manufactured to ASME B1.20.1, so dimensions are interchangeable between suppliers when you quote the standard on your order.

What are NPT Pipe Thread Fittings used for?

Joining and sealing fluid or pneumatic lines. They are supplied to ASME B1.20.1.

Can I get a quote for NPT Pipe Thread Fittings in the size and material I need?

Yes. Use the technical drawing and quote form on this page to set the size and options, then send the exact configuration to our team for pricing and lead time.