Types Of Pipe Threads

Resource Description

Types Of Pipe Threads

It is significant to determine several specific pipe thread variations you require according to the equipment to operate perfectly. Air cylinders, valves, and air preparation units are pneumatic components that need specific types of pipe threads to be equipped with. For instance, pneumatic stuff is required to be equipped with NPT, PT, or G pipe threads. Selecting the proper pipe thread type will offer you the proper performance of your equipment.

At the first sight, pipe threads may seem to be similar. However, if you look closer, you will notice several differences between them. For instance, several pipe threads may have differences from each other by shape, type of angle, or thread pitches. The article includes several types of most common pipe threads, including NPT/NPTF, BSPP (or G), BSPT, PT, Metric (M), and SAE. You will need only two simple tools: a caliper and a pitch gauge.

Pipe Thread Determining Tools

Caliper

A caliper is a useful tool that determines the outside diameter of the male thread, and the inside diameter of the female thread. Applying the caliper will provide you with the most accurate measurements, however, if you don’t have one, you may use a straight steel ruler. Nevertheless, you may use the innovative digital caliper for easier work.

Pitch Gauge

A pitch gauge is a tool that helps to determine the pipe threads per inch. This tool determines the distance between the threads for the metric pipe threads.

Identifying Types Of Threads

Pipe threads can be male or female and this is an easy differentiation to understand. Male means that the thread is on the outside of the fitting, it looks like a bolt. The female thread looks like a nut, and it is on the inside of the fitting.

The other aspect you should know is the pitch. Thread pitch is the space among threads. To determine it, you should use a gauge pitch tool or caliper to identify the distance between the threads according to the length of the fitting. Metric threads are identified by the millimetric distance between them, while the other pitch of the thread is determined by the number of threads per inch. For instance, the distance between threads is 1 millimeter, so the pitch is 1 millimeter.

Parallel threads types:

● UN/UNF (SAE)

● BSPP

● metric parallel

Parallel threads

Parallel thread example

Tapered threads types:

● NPT/NPTF (American Pipe)

● BSPT (British Pipe)

● metric tapered

Tapered threads

Tapered thread example

Apply the caliper to determine the outside diameter of the male thread and the inside diameter of the female thread. Please note that small differences between measurement and size charts are due to various thread manufacturers.

The design of each thread can be tapered or parallel. There are two major classifications of pipe threads: parallel and tapered. The parallel thread is the type where the diameter has the same length as the thread. The tapered thread has a bigger diameter length than the length of the tool.

A flank angle and tapered angle are the only types of angles, even screws with tapered designs are also created with a taper angle. The flank angle relates to the angle between the flank and the cross-cutting line to the axis of the thread. The tapered angle is the angle between the taper and the center axis of the pipe.

How To Identify The Pipe Thread?

Pick up the information you have found out recently and select the proper pipe thread according to the Nominal Dimensions of Standard Threads chart. For example, according to the chart ½-14 NPT determines the pipe thread with nominal inside the diameter of ½ inch and 14 threads to the inch.

Size Pipe OD Tapered Threads Straight Threads
NPT BSPTr NPSH NPSM NST (NH) BSPP
TPI TPI TPI ODM (max) IDF (min) TPI ODM (max) IDF (min) TPI ODM (max) IDF (min) TPI ODM (max) IDF (min)
1⁄8" .405 27.0 28       27.0 0.397 0.358         0.383 0.337
1⁄4" .540 18.0 19       18.0 0.526 0.468         0.516 0.450
3⁄8" .675 18.0 19       18.0 0.662 0.603         0.656 0.588
1⁄2" .840 14.0 14 14.0 0.8248 0.7395 14.0 0.823 0.747         0.825 0.733
3⁄4" 1.050 14.0 14 14.0 1.0353 0.9500 14.0 1.034 0.958         1.041 0.950
1" 1.315 11.5 11 11.5 1.2951 1.1921 11.5 1.293 1.201 8.0 1.375 1.2246 11 1.309 1.193
1 1⁄4" 1.660 11.5 11 11.5 1.6399 1.5369 11.5 1.638 1.546       11 1.650 1.534
1 1⁄2" 1.900 11.5 11 11.5 1.8788 1.7758 11.5 1.877 1.785 9.0 1.990 1.8577 11 1.882 1.766
2" 2.375 11.5 11 11.5 2.3528 2.2498 11.5 2.351 2.259       11 2.347 2.231
2 1⁄2" 2.875 8.0 11 8.0 2.8434 2.6930 8.0 2.841 2.708 7.5 3.068 2.9104 11 2.960 2.844
3" 3.500 8.0 11       8.0 3.467 3.334 6.0 3.623 3.5306 11 3.460 3.344
4" 4.500 8.0 11       8.0 4.466 4.333 4.0 5.010 4.7111 11 4.450 4.334
4 1⁄2"                   4.0 5.760 5.4611      
5" 5.563 8.0 11       8.0 5.528 5.395 4.0 6.260 5.9602 11 5.450 5.359
6" 6.625 8.0 11       8.0 6.585 6.452 4.0 7.025 6.7252 11 6.450 6.359
8" 8.625 8.0                          
10" 10.750 8.0                          
12" 12.750 8.0                          

• ODM = Outside Diameter of the male; • IDF = Inside Diameter of the female; • TPI = Threads Per Inch; • GHT (3/4") -- 1.0625 ODM, 11-1/2 TPI; • Female NPT (Tapered Pipe) thread is not available on hose swivel nuts.

Identify The Pipe Thread Compatibility

When you find out all the details you need to identify the proper pipe thread you should make sure the fitting provides a compatible connection. The best solution to identify male and female fittings is to use this chart.

Abbreviation System Name Compatibility Seal Method
BSPP British Standard Pipe Parallel male BSPP with female BSPP washer
female BSPP with male BSPP washer
female BSPP with male BSPP washer
BSPTr British Standard Pipe Taper male BSPTr with female BSPTr thread
male BSPTr with female BSPP washer

female BSPTr with male BSPTr

female BSPTr not compatible with male BSPP

thread
CHT American Standard Fire Hose Thread (1" National Hose Thread is Chemical Hose Thread, also known as Booster Hose Thread) 1" male NH (NST) with 1" female NH (NST) washer
1" female NH (NST) with 1" female NH (NST) washer
1" thread is used on both 3/4" hose & 1" hose not compatible
GHT Garden Hose Thread male GHT with female GHT washer
female GHT with male GHT washer
thread is same for all size hose not compatible
IPS Iron Pipe Straight Thread

generic name for Straight Pipe Thread

see NPSH for compatibility

washer
IPT Iron Pipe Thread generic name for All Pipe Thread more information required
JIC Joint Industrial Committee used with other mating JIC threads mechanical
NH or NST American Standard Fire Hose Thread Coupling Thread (National Hose thread also known as National Standard Thread) male NH (NST) with female NG (NST) washer

female NH (NST) with male NG (NST)

thread pitch and diameters of fire threads may vary according to local and municipal regulations

not compatible with other systems

washer
NPT American Standard Taper Pipe Thread (National Pipe Tapered) male NPT with female NPT thread
male NPT with female NPTF thread
male NPT with female NPSM washer
male NPT with female NPSH washer
female NPT with male NPT thread

female NPT with male NPTF

female NPT not compatible with male NPSM or male NPSH

thread
NPTF American Standard Taper Pipe Thread (National Pipe Tapered) male NPTF with female NPTF thread
male NPTF with female NPT thread
male NPTF with female NPSM washer
male NPTF with female NPSH washer
female NPTF with male NPTF thread
female NPTF with male NPT thread

female NPTF with male NPSM or NPSH

NPTF with NPTF threads do not require sealant for the initial use, after that, sealant is required

not compatible
NPSH American Standard Straight Pipe for Hose Couplings (National Pipe Straight Hose) male NPSH with female NPSH washer
female NPSH with male NPSH washer
female NPSH with male NPT washer
female NPSH with male NPTF washer
female NPSH with male NPSM washer
NPSM American Standard Straight Mechanical Joints (National Pipe Straight Mechanical) male NPSM with female NPSM Seal can be either mechanical or washer. Mating fittings must be of same type.
male NPSM with female NPSH
female NPSM with male NPSM
male NPSM with female NPT
male NPSM with female NPTF
SIPT Straight Iron Pipe Thread generic name for Straight Pipe Thread washer
TIPT Tapered Iron Pipe Thread generic name for Tapered Pipe Thread thread
NYFD NYFD Fire Department straight thread used in New York City washer
Chicago Chicago Fire Department straight thread used in Chicago washer

Conclusion

Every worker knows it is to understand and be able to determine each type of thread. The most common types of threads are applied in the plumbing industry: UN/UNF.

Parallel Unified Thread Standard (UN) bolts are types of pipe threads applied in the plumbing systems in the US, Canada, and the UK. UN can be graded by the number of pipe threads per inch. For example, the pipe thread determined as UNF has the same length as UNC and the only difference is the higher amount of threads per inch. Moreover, UNEF is similar to UNF, but it also has a higher amount of threads per inch for each fitting size.

There are also 6 types of pipe thread that you should differentiate between them and their functions. When you have determined the type of device you need, you should fix it properly for the correct work.