Thread ID Made Easy

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When it comes to hose and tube fittings, there are a number of different types of threads available. The number of fitting end options can make selecting the most appropriate fitting thread type a daunting task. The reliability of the fitting connection depends on selecting what&#;s optimal for the application.  First, we will educate you about six types of common thread types. Second, we will guide you through the thread identification process.

Six Most Common Types of Threads

When it comes to different thread types, most people who work in the fluid-power industry will recognize American pipe threads (NPT/NPTF) as well as SAE or Unified threads (UN/UNF). However, threads and connections are divided into six main types:

1. UN/UNF
2. NPT/NPTF
3. BSPP (BSP, parallel)
4. BSPT (BSP, tapered)
5. metric parallel
6. metric tapered

Let&#;s learn the difference between each one of them.

How to identify different types of
threads in four easy steps

Before you start, make sure you have two thread identifying tools on hand:

• Pitch Gauge

A pitch gauge is a tool used to measure the distance between the crests of threads. For NPT, UN/UNF, BSPP, and BSPP we measure the number of threads per inch. If you have the metric threads, the pitch gauge identifies the distance between each individual crest in millimeters.

• Caliper

A caliper is used to measure the diameter of a thread. For male threads, it measures the outside diameter, for a female thread &#; inside diameter, respectively. For advanced users, a digital caliper is available from multiple retailers. It saves your time and simplifies the process.

STEP 1. Parallel thread vs. tapered thread. Let&#;s learn the difference.

Parallel threads include:

• UN/UNF
• BSPP
• metric parallel

Tapered threads include:

• NPT/NPTF
• BSPT
• metric tapered

To identify whether the thread is tapered or parallel, look at the diameter of your thread. If the thread diameter gets thinner towards the end, you are looking at a tapered thread. On the contrary, if the thread diameter is the same at the top and the bottom of the thread, you have the parallel thread. See the graphics below to learn the visual difference between tapered and parallel threads.  Using a known parallel, like a pair of calipers can help to show if a fitting is tapered.  If the threads touch the entire length of the calipers, it is parallel but if it rocks you have tapered threads.

STEP 2. Determine the Pitch

Use a thread pitch gauge tool to determine the size of the thread. Thread pitch gauge helps you to accurately measure and calculate the number of threads within a given distance.

Try a number of gages from the pitch gauge tool against the white background before deciding which one fits your thread the best. Look at the common pitch sizes for each of the different thread types in the table below.

Thread Type Pitch Size UN/UNF
(SAE) 12, 14, 16, 18, 20, 24 NPT/NPTF
(American Pipe) 11 ½, 14, 18, 27 BSPP
(British Pipe) 11, 14, 19, 28 BSPT
(British Pipe) 11, 14, 19, 28 Metric Parallel 1.0, 1.5, 2.0 Metric Tapered 1.0, 1.5, 2.0

STEP 3. Thread size matters

When it comes to determining the thread size, you have two approaches at your disposal. Before you start, determine if your thread is a pipe thread (NPT/NPTF, BSPT, BSPP) or not (UN/UNF, Metric Parallel, Metric Tapered). Remember that tapered thread can both be a pipe thread or not.

If you have a pipe thread, compare the size of the thread with a nominal size profile, as shown in Figure 1. For non-pipe thread (UN/UNF, Metric Parallel, Metric Tapered), use the caliper tool to measure the outside diameter of the tread.

STEP 4. Designate the thread

This step involves designating the thread according to the industry standards for further use. Start with identifying the tread size (nominal or actual), then write down the type and the pitch (if applies). See the examples in the table below under STEP 4:

The company is the world’s best pipe thread types supplier. We are your one-stop shop for all needs. Our staff are highly-specialized and will help you find the product you need.

Additional reading:
Advantages of Post Tensioning Thread Type Step 1. Tapered or parallel Step 2. Determine the pitch Step 3. Thread size matters Step 4. Designate the thread UN/UNF (SAE) Parallel 12, 14, 16, 18, 20, 24 Measure with caliper Size-pitch, type 3/4-16 UN/UNF NPT/NPTF Tapered 11 ½, 14, 18, 27 Compare with profile Size-pitch, type 1/4-18 NPT BSPP Parallel 11, 14, 19, 28 Compare with profile G, size* G1/8 BSPT Tapered 11, 14, 19, 28 Compare with profile R, size* R1/2 Metric Parallel Parallel 1.0, 1.5, 2.0 Measure with caliper M, size X pitch M14X1.5 Metric Tapered Tapered 1.0, 1.5, 2.0 Measure with caliper M, size x pitch, keg or Taper, M10 x 1 keg or Taper

Summary

To sum up, the thread ID process consists of four simple steps. We have learned about different types of threads, including tapered and parallel, pitch sizes, thread sizes, and industry standards when it comes to identifying thread types. Remember that selecting the wrong part can result in physical or property damage if resulting in a leak, so always consult you, fluid connector specialist, if you have any questions to prevent your equipment from breaking or malfunctioning.

Pipe Thread Acronyms:

Abbreviation System Name BSP British Standard Pipe BSPP British Standard Pipe Parallel Thread BSPT British Standard Pipe Taper Thread NPT National Pipe Thread NPTF National Pipe Thread Fuel

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In the vast world of fittings, threaded fittings play a major role. They are ideal for fast assembly and disassembly and give you an opportunity to solve any possible faults, maintenances and malfunction.  In particular, two types of threads are mostly used, especially in hydraulics: BSP thread and NPT thread.

NPT Thread

NPT thread accounts for National Pipe Thread and represents the American standard complying with the norm ANSI B1.20.1. After the BSP thread, it is probably the most used one in the field of hydraulic fittings. It features a 60°- thread angle and it is characterized by a conical thread and not cylindrical one. They usually ensure a higher water tightness, even though the use of a gaskets is still recommended. You can refer it to as MPT, MNPT or NPT (M) for male external threads and FPT, FNPT or NPT (F) for internal female threads. Both threads have the same spacing, angle (60 degrees) and form (flat peaks and depressions).

BSP Thread 

The BSP thread form stands for the British Standard Pipe and is common in Australia and in the Commonwealth countries. BSP is based on threads following standard ISO 228 and Whitworth. The BSP threads were adopted at an international level for the interconnection and sealing of pipes and fittings. The BSP standard incorporates the threads following standard Whitworth, which was developed in as the first thread standard in the world and it is now extremely popular at an international level for the connections of pipes and fittings.

There are two types of BSP threads:

&#; BSPP (British Standard Pipe Parallel). Reference standard: BS ̶ ISO -6. This thread is used in Europe and has a cylindrical thread resulting from the &#;Whitworth&#; thread, but with different sizes and spacing. It is known as GAS cylindrical thread. The mechanical seal is reached with a 60° concave flaring on the male fitting. The seal with an O &#; ring gasket is located on the female fitting cone. The seal with flat seat on the male and female parts is guaranteed with a copper gasket.

&#; BSPT (British Standard Pipe Tapered). It is used in Europe and has a conic GAS thread. The seal is reached with the deformation of threads between the male and female part.  BSPT is similar to NPT, but there is an important difference. The thread angle is 55 degrees instead of 60 degrees, which is usual for NPT. Therefore, an NPT fitting will be inserted in a BSPT connection or vice versa, but they will not be sealed. The BSPT fittings are a common  connection method in China and Japan, but they are very rarely used in North America, unless the equipment to which they are connected has been imported.

What are the main differences between the two standards?

The main difference between BSP and NPT threads is mainly connected to &#;where&#; than to &#;what&#;. While NPT is prevalent in the USA and Canada, BSP is the main standard in the United Kingdom, Europe, Asia, Australia, New Zealand, South Africa and many other countries. Furthermore, to sum up, the NPT and BSP threads are not interchangeable due to the differences in the thread forms. The NPT threads are sharp in peaks and valleys, where BSP threads are rounded. In particular, the NPT thread angle is 60 degrees compared to the BSP 55-degree angle.

Right for this last difference, it is good to choose the suitable thread in order not to cause any fluid leakages or faults under pressure.

Are you interested in learning more about Threaded Fitting? Contact us today to secure an expert consultation!