British Standard Pipe

British Standard Pipe (BSP) is a family of technical standards for screw threads that has been adopted internationally for interconnecting and sealing pipes and fittings by mating an external (male) thread with an internal (female) thread. It has been adopted as standard in plumbing and pipe fitting, except in the United States, where NPT and related threads are the standard used.


BSPP Male Straight Thread
BSPP fitting

Two types of threads are distinguished:

  • Parallel (straight) threads, British Standard Pipe Parallel thread (BSPP; originally also known as[1] British Standard Pipe Fitting thread/BSPF and British Standard Pipe Mechanical thread/BSPM), which have a constant diameter; denoted by the letter G.
  • Taper threads, British Standard Pipe Taper thread (BSPT), whose diameter increases or decreases along the length of the thread; denoted by the letter R.
Colder BSPT Threads
BSPT Pipe Threads.[2]

These can be combined into two types of joints:

Jointing threads
These are pipe threads where pressure-tightness is made through the mating of two threads together. They always use a taper male thread, but can have either parallel or taper female threads. (International standards require all female threads to be parallel.)
Longscrew threads
These are parallel pipe threads used where a pressure-tight joint is achieved by the compression of a soft material (such as an o-ring seal or a washer) between the end face of the male thread and a socket or nipple face, with the tightening of a backnut.

Thread form

The thread form follows the British Standard Whitworth standard:

  • Symmetrical V-thread in which the angle between the flanks is 55° (measured in an axial plane)
  • One-sixth of this sharp V is truncated at the top and the bottom
  • The threads are rounded equally at crests and roots by circular arcs ending tangentially with the flanks where r ≈ 0.1373P
  • The theoretical depth of the thread is therefore 0.6403 times the nominal pitch h ≈ 0.6403P

Pipe thread sizes

At least 41 thread sizes have been defined, ranging from 116 to 18, although of these only 15 are included in ISO 7 and 24 in ISO 228.[3][4][5][6] The size number was originally based on the inner diameter (measured in inches) of a steel tube for which the thread was intended, but contemporary pipes tend to use thinner walls to save material, and thus have an inner diameter larger than this nominal size. In the modern standard metric version, it is simply a size number, where listed diameter size is the major outer diameter of the external thread. For a taper thread, it is the diameter at the "gauge length" (plus/minus one thread pitch) from the small end of the thread. The taper is 1 to 16, meaning that for each 16 units of measurement increase in the distance from the end, the diameter increases by 1 unit of measurement.

Tapping drill
R 95% G 80%
(in) (in−1) (mm) (in) (mm) (in) (mm) (in) (mm) (mm) (mm)
116 28 0.907 0.3041 7.723 0.2583 6.561 532 4.0 6.6 6.8
18 28 0.907 0.3830 9.728 0.3372 8.566 532 4.0 8.6 8.8
14 19 1.337 0.5180 13.157 0.4506 11.445 0.2367 6.0 11.5 11.8
38 19 1.337 0.6560 16.662 0.5886 14.950 14 6.4 15.0 15.3
12 14 1.814 0.8250 20.955 0.7335 18.631 0.3214 8.2 18.7 19.1
58 14 1.814 0.9020 22.911 0.8105 20.587 0.3214 8.2 20.7 21.1
34 14 1.814 1.0410 26.441 0.9495 24.117 38 9.5 24.2 24.6
78 14 1.814 1.1890 30.201 1.0975 27.877 38 9.5 28.0 28.3
1 11 2.309 1.3090 33.249 1.1926 30.291 0.4091 10.4 30.4 30.9
1 18 11 2.309 1.4920 37.897 1.3756 34.939 0.4091 10.4 35.1 35.5
1 14 11 2.309 1.6500 41.910 1.5335 38.952 12 12.7 39.1 39.5
1 38 11 2.309 1.7450 44.323 1.6285 41.365 12 12.7 41.5 42.0
1 12 11 2.309 1.8820 47.803 1.7656 44.845 12 12.7 45.0 45.4
1 58 11 2.309 2.0820 52.883 1.9656 49.926 58 15.9 50.1 50.5
1 34 11 2.309 2.1160 53.746 1.9995 50.788 58 15.9 50.9 51.4
1 78 11 2.309 2.2440 56.998 2.1276 54.041 58 15.9 54.2 54.6
2 11 2.309 2.3470 59.614 2.2306 56.656 58 15.9 56.8 57.2
2 14 11 2.309 2.5870 65.710 2.4706 62.752 1116 17.5 62.9 63.3
2 12 11 2.309 2.9600 75.184 2.8435 72.226 1116 17.5 72.4 72.8
2 34 11 2.309 3.2100 81.534 3.0935 78.576 1316 20.6 78.7 79.2
3 11 2.309 3.4600 87.884 3.3435 84.926 1316 20.6 85.1 85.5
3 14 11 2.309 3.7000 93.980 3.5835 91.022 78 22.2 91.2 91.6
3 12 11 2.309 3.9500 100.330 3.8335 97.372 78 22.2 97.5 98.0
3 34 11 2.309 4.2000 106.680 4.0835 103.722 78 22.2 103.9 104.3
4 11 2.309 4.4500 113.030 4.3335 110.072 1 25.4 110.2 110.7
4 12 11 2.309 4.9500 125.730 4.8335 122.772 1 25.4 122.9 123.4
5 11 2.309 5.4500 138.430 5.3335 135.472 1 18 28.6 135.6 136.1
5 12 11 2.309 5.9500 151.130 5.8335 148.172 1 18 28.6 148.3 148.8
6 11 2.309 6.4500 163.830 6.3335 160.872 1 18 28.6 161.0 161.5
7 10 2.540 7.4500 189.230 7.3220 185.979 1 38 34.9 186.1 186.6
8 10 2.540 8.4500 214.630 8.3220 211.379 1 12 38.1 211.5 212.0
9 10 2.540 9.4500 240.030 9.3220 236.779 1 12 38.1 236.9 237.4
10 10 2.540 10.4500 265.430 10.3220 262.179 1 58 41.3 262.3 262.8
11 8 3.175 11.4500 290.830 11.2900 286.766 1 58 41.3 287.0 287.6
12 8 3.175 12.4500 316.230 12.2900 312.166 1 58 41.3 312.4 313.0
13 8 3.175 13.6800 347.472 13.5200 343.408 1 58 41.3 343.6 344.2
14 8 3.175 14.6800 372.872 14.5200 368.808 1 34 44.5 369.0 369.6
15 8 3.175 15.6800 398.272 15.5200 394.208 1 34 44.5 394.4 395.0
16 8 3.175 16.6800 423.672 16.5200 419.608 1 78 47.6 419.8 420.4
17 8 3.175 17.6800 449.072 17.5200 445.008 2 50.8 445.2 445.8
18 8 3.175 18.6800 474.472 18.5200 470.408 2 50.8 470.6 471.2

These standard pipe threads are formally referred to by the following sequence of blocks:

  • the words, Pipe thread,
  • the document number of the standard (e.g., ISO 7 or EN 10226)
  • the symbol for the pipe thread type:
    • G, external and internal parallel (ISO 228)
    • R, external taper (ISO 7)
    • Rp, internal parallel (ISO 7/1)
    • Rc, internal taper (ISO 7)
    • Rs, external parallel
  • the thread size

Threads are normally right-hand. For left-hand threads, the letters, LH, are appended.

Example: Pipe thread EN 10226 Rp ​2 12

The terminology for the use of G and R originated from Germany (G for gas, as it was originally designed for use on gas pipes; R for rohr, meaning pipe.)

Pipe and fastener dimensions

G / R
Typ. nut
Corresponding pipe
DN OD Wall
(in) (mm) (mm) (mm) (mm)
116 3
18 15 6 10.2 2
14 19 8 13.5 2.3
38 22 or 23 10 17.2 2.3
12 27 15 21.3 2.6
34 32 20 26.9 2.6
1 43 25 33.7 3.2
1 14 53 32 42.4 3.2
1 12 57 40 48.3 3.2
2 70 50 60.3 3.6
2 12 65 76.1 3.6
3 80 88.9 4
4 100 114.3 4.5
5 125 139.7 5
6 150 168.3 5

ISO 7 (Pressure Tight threads)

The standard ISO 7 - Pipe threads where pressure-tight joints are made on the threads consists of the following parts:

  • ISO 7-1:1994 Dimensions, tolerances and designation
  • ISO 7-2:2000 Verification by means of limit gauges

ISO 228 (Non Pressure Tight Threads)

The standard ISO 228 - Pipe threads where pressure-tight joints are not made on the threads consists of the following parts:

  • ISO 228-1:2000 Dimensions, tolerances and designation
  • ISO 228-2:1987 Verification by means of limit gauges

See also


  1. ^ "BSPM = British Standard Pipe Mechanical". Retrieved 14 July 2016.
  2. ^ "Archived copy" (PDF). Archived from the original (PDF) on 2013-10-07. Retrieved 2013-12-27.CS1 maint: Archived copy as title (link)
  3. ^ maryland metrics. "Maryland Metrics thread data charts". Retrieved 14 July 2016.
  4. ^ "RoyMech: Pipe Threads". Retrieved 14 July 2016.
  5. ^ "How to ID British (BSP) Threads" (PDF). Retrieved 20 November 2017.
  6. ^ "BSP Thread data". Retrieved 2016-07-15.

External links


BSPP may stand for:

Brigade des Sapeurs-Pompiers de Paris, the Paris Fire Brigade

the British Society for Plant Pathology

British standard parallel pipe thread, see British standard pipe thread

the Burma Socialist Programme Party

BSPP (drug)

British Standard Brass

British Standard Brass or British Brass Thread is an imperial unit based screw thread. It adopts the Whitworth thread form with a pitch of 26 threads per inch and a thread angle of 55 degrees for all diameters. It is often wrongly called British Standard Brass but is not actually covered by a British Standard.

The reason for adopting 26 tpi, is brass tube has a relatively similar wall thickness irrespective of the outside diameter of the tube, therefore as BSW thread depths are determined by the threads per inch, a lower tpi would reduce the strength of the tube or cut right through it. Brass tube threads can be confused with the British Standard Cycle thread, one of which that is most common is also 26 tpi. The difference being the thread angle of the British Standard Cycle is the same as the metric thread angle of 60 degrees.

Nominal sizes are usually in the range ​1⁄8 to 2 inches.

British Standard Whitworth

British Standard Whitworth (BSW) is an imperial-unit-based screw thread standard.

Coupling (piping)

A coupling (or coupler) (used in piping or plumbing) is a very short length of pipe or tube, with a socket at one or both ends that allows two pipes or tubes to be joined, welded (steel), brazed or soldered (copper, brass etc.) together.

Alternatively it is a short length of pipe with two female National pipe threads (NPT) (in North American terms, a coupler is a double female while a nipple is double male) or two male or female British standard pipe threads.

If the two ends of a coupling are different (e.g. one BSP threaded and one NPT threaded), then it is usually referred to as an adapter. Another variation is one plain socket and one threaded socket. Yet another variation would be 3/4" NPT to 1/2" NPT.

When the two ends use the same connection method but are of a different size, the terms reducing coupling or reducer are used.

Garden hose

A garden hose, hosepipe, or simply hose is a flexible tube used to convey water. There are a number of common attachments available for the end of the hose, such as sprayers and sprinklers (which are used to concentrate water at one point or to spread it over a large area). Hoses are usually attached to a hose spigot or tap.

ISO metric screw thread

The ISO metric screw threads are the worldwide most commonly used type of general-purpose screw thread. They were one of the first international standards agreed when the International Organization for Standardization (ISO) was set up in 1947.The "M" designation for metric screws indicates the nominal outer diameter of the screw, in millimeters (e.g., an M6 screw has a nominal outer diameter of 6 millimeters).

JIC fitting

JIC fittings, defined by the SAE J514 and MIL-DTL-18866 standards, are a type of flare fitting machined with a 37-degree flare seating surface. JIC (Joint Industry Council) fittings are widely used in fuel delivery and fluid power applications, especially where high pressure (up to 10,000 psi) is involved. The SAE J514 standard replaces the MS16142 military specification, although some tooling is still listed under MS16142. JIC fittings are dimensionally identical to AN (Army-Navy) fittings, but are produced to less exacting tolerances and are generally less costly. SAE 45-degree flare fittings are similar in appearance, but are not interchangeable, though dash sizes 2, 3, 4, 5, 8, 10, 14, and 16 share the same thread size. Some couplings may have dual machined seats for both 37-degree and 45-degree flare seats.

Komatsu and JIS (Japanese Industrial Standard) fittings have flare ends similar to JIC fittings. Komatsu and JIS both use a 30-degree flare seating surface. The only difference is Komatsu uses millimeter thread sizes while JIS use a BSP (British Standard Pipe) thread.

JIC fitting systems have three components that make a tubing assembly: fitting, flare nut, and sleeve. As with other flared connection systems, the seal is achieved through metal-to-metal contact between the finished surface of the fitting nose and the inside diameter of the flared tubing. The sleeve is used to evenly distribute the compressive forces of the flare nut to the flared end of the tube. Materials commonly used to fabricate JIC fittings include forged carbon steel, forged stainless steel, forged brass, machined brass, Monel and nickel-copper alloys.

JIC fittings are commonly used in the Fluid Power industry in a diagnostic and test-point setting. A three-way JIC coupling provides a port inline of circuit by which a user can connect a measurement or diagnostic device to take pressure readings and perform circuit and system diagnostics.

List of drill and tap sizes

Below is a comprehensive drill and tap size chart for all drills and taps, imperial and metric, up to 36.5 millimetres (1.44 in) in diameter.

In manufactured parts, holes with female screw threads are often needed; they accept male screws to facilitate the building and fastening of a finished assembly. One of the most common ways to produce such threaded holes is to drill a hole of appropriate size with a drill bit and then tap it with a tap. Each standard size of female screw thread has one or several corresponding drill bit sizes that are within the range of appropriate size—slightly larger than the minor diameter of the mating male thread, but smaller than its pitch and major diameters. Such an appropriately sized drill is called a tap drill for that size of thread, because it is a correct drill to be followed by the tap. Many thread sizes have several possible tap drills, because they yield threads of varying thread depth between 50% and 100%. Usually thread depths of 60% to 75% are desired.

People frequently use a chart such as this to determine the proper tap drill for a certain thread size or the proper tap for an existing hole.

National pipe thread

American National Standard Pipe Thread standards, often called national pipe thread standards for short, are U.S. national technical standards for screw threads used on threaded pipes and pipe fittings. They include both tapered and straight thread series for various purposes including rigidity, pressure-tight sealing, or both. The various types are each named with a symbol and a full name; examples of the symbols include NPT, NPS, NPTF, NPSC, and others.

MIP is an acronym for male iron pipe, and FIP is an acronym for female iron pipe.Outside the United States, some US pipe threads are found, as well as many British Standard Pipe threads and ISO 7-1, 7-2, 228-1, and 228-2 threads.

Nominal Pipe Size

Nominal Pipe Size (NPS) is a North American set of standard sizes for pipes used for high or low pressures and temperatures. "Nominal" refers to pipe in non-specific terms and identifies the diameter of the hole with a non-dimensional number (for example – 2-inch nominal steel pipe" consists of many varieties of steel pipe with the only criterion being a 2.375-inch (60.3 mm) outside diameter). Specific pipe is identified by pipe diameter and another non-dimensional number for wall thickness referred to as the Schedule (Sched. or Sch., for example – "2-inch diameter pipe, Schedule 40"). NPS is often incorrectly called National Pipe Size, due to confusion with the American standard for pipe threads, "national pipe straight", which also abbreviates as "NPS". The European and international designation equivalent to NPS is DN (diamètre nominal/nominal diameter/Durchmesser nach Norm), in which sizes are measured in millimetres, see ISO 6708. The term NB (nominal bore) is also frequently used interchangeably with NPS.

In March 1927 the American Standards Association authorized a committee to standardize the dimensions of wrought steel and wrought iron pipe and tubing. At that time only a small selection of wall thicknesses were in use: standard weight (STD), extra-strong (XS), and double extra-strong (XXS), based on the iron pipe size (IPS) system of the day. However these three sizes did not fit all applications. Also, in 1939, it was hoped that the designations of STD, XS, and XXS would be phased out by schedule numbers, however those original terms are still in common use today (although sometimes referred to as standard, extra-heavy (XH), and double extra-heavy (XXH), respectively). Since the original schedules were created, there have been many revisions and additions to the tables of pipe sizes based on industry use and on standards from API, ASTM, and others.Stainless steel pipes, which were coming into more common use in the mid 20th century, permitted the use of thinner pipe walls with much less risk of failure due to corrosion. By 1949 thinner schedules 5S and 10S, which were based on the pressure requirements modified to the nearest BWG number, had been created, and other "S" sizes followed later. Due to their thin walls, the smaller "S" sizes can not be threaded together according to ASME code, but must be fusion welded.

North American Fire Hose Coupler Incompatibilities

Despite fire hose and hydrant coupler standardization efforts that are at least 144 years old, there remain significant areas in Canada, the United States, and Mexico that use fire hose and hydrant threads and other couplings that are incompatible with those used by neighboring fire departments. This is notable because the first fire hydrant was invented by Manhattan fire fighter George Smith in 1817, making these devices 200 years old.These incompatibilities have led to well-documented loss of life and buildings, including the Great Boston fire of 1872, the Great Baltimore Fire in 1904, and the Oakland Firestorm of 1991. As of 2017, San Francisco still maintains fire hydrants with a size and thread that are incompatible with those used by most or all other nearby fire departments that would respond in mutual aid conditions, such as occurred during the 1989 Loma Prieta earthquake.

As a result of the 1872 Boston fire, the International Association of Fire Engineers designed and published a fire hydrant coupling standard. As a result of the 1904 Baltimore fire, the National Fire Protection Association formed a committee, and in 1905 published its first report on the subject, which would eventually become an official standard, NFPA 1963. This standard specified that each fire hydrant have one large diameter pumper (a.k.a. "steamer") port 4.5 inches in diameter with 4 threads per inch (meant for supplying water to a pumper truck or other high-capacity distribution device), and two medium-diameter ports, each 2.5 inches with 7.5 threads per inch, meant for supplying individual attack hoses directly.

During at least two periods, specialized thread-adjusting tool sets were developed to enable fire departments using diameters and threads similar to but incompatible with the NFPA standard to convert them to the national standard. The first of these was used around 1911, developed by the Greenfield Tap and Die Corporation, and documented as late as 1922, wherein it was claimed that the 70% of municipalities not already using the NFPA standard threads could convert their couplings to the new standard. Around 1950, San Diego Battalion Chief and Master Fire Mechanic Robert Ely developed a similar machine, now known as the “Ely Fire Hose Thread Standardizer" that could do the job in 90 seconds.One of the reasons for the incompatibilities is that there are three U.S. national hose threaded hose coupling standards. NFPA 1963, which defines the vast majority of fire hose couplings in existence, and ANSI-ASME B1.20.7, which defines garden hose thread (sometimes used by wildland fire fighting crews) along with (non-tapered) iron pipe thread, and ANSI B26, FIRE-HOSE COUPLING SCREW THREAD FOR ALL CONNECTIONS HAVING NOMINAL INSIDE DIAMETERS OF 2 ½, 3, 3 ½, AND 4 ½ INCHES".

Note: the straight iron pipe thread is a temporary connection and seals with a gasket, just like garden hose threads and fire hose threads, and is distinct from tapered iron pipe thread (NPT), which is a permanent connection sealed by the threads in conjunction with pipe dope or teflon tape wrapped around the threads. However, because the straight and tapered iron pipe threads differ only in their taper, it is possible for small NPSH/SIPT female hose couplings in sizes ​1⁄2″ to 4″ (inclusive) to be joined to NPT male pipe ends. The connection uses a gasket to seal, and is temporary.

Pipe (fluid conveyance)

A pipe is a tubular section or hollow cylinder, usually but not necessarily of circular cross-section, used mainly to convey substances which can flow — liquids and gases (fluids), slurries, powders and masses of small solids. It can also be used for structural applications; hollow pipe is far stiffer per unit weight than solid members.

In common usage the words pipe and tube are usually interchangeable, but in industry and engineering, the terms are uniquely defined. Depending on the applicable standard to which it is manufactured, pipe is generally specified by a nominal diameter with a constant outside diameter (OD) and a schedule that defines the thickness. Tube is most often specified by the OD and wall thickness, but may be specified by any two of OD, inside diameter (ID), and wall thickness. Pipe is generally manufactured to one of several international and national industrial standards. While similar standards exist for specific industry application tubing, tube is often made to custom sizes and a broader range of diameters and tolerances. Many industrial and government standards exist for the production of pipe and tubing. The term "tube" is also commonly applied to non-cylindrical sections, i.e., square or rectangular tubing. In general, "pipe" is the more common term in most of the world, whereas "tube" is more widely used in the United States.

Both "pipe" and "tube" imply a level of rigidity and permanence, whereas a hose (or hosepipe) is usually portable and flexible. Pipe assemblies are almost always constructed with the use of fittings such as elbows, tees, and so on, while tube may be formed or bent into custom configurations. For materials that are inflexible, cannot be formed, or where construction is governed by codes or standards, tube assemblies are also constructed with the use of tube fittings.

Propane, butane, and LPG container valve connections

Major differences between connectors of containers used for transport and storage of liquefied petroleum gas, propane and butane exist between countries. Even within a single country more than one type can be in use for a specific application. This requires adequate tooling and adapters for replenishment in multiple countries. For example for overlanders and users of autogas traveling with a container originating in one country to other parts of the world this is a major concern. This article describes existing standards and the standards in use for a number of countries. For disposable containers the availability per country is described. Filling stations may be able and allowed to fill foreign containers if adequate adapters. are available. Adapters are provided by a.o. camping stores. The iOverlander database maintained by travelers, My LPG and the Facebook group "Cooking Gas Around the World" provide more information about individual sources per country. Much general information about global LPG use and standardization is available from the World LPG Association and the AEGPL

Screw thread

A screw thread, often shortened to thread, is a helical structure used to convert between rotational and linear movement or force. A screw thread is a ridge wrapped around a cylinder or cone in the form of a helix, with the former being called a straight thread and the latter called a tapered thread. A screw thread is the essential feature of the screw as a simple machine and also as a fastener.

The mechanical advantage of a screw thread depends on its lead, which is the linear distance the screw travels in one revolution. In most applications, the lead of a screw thread is chosen so that friction is sufficient to prevent linear motion being converted to rotary, that is so the screw does not slip even when linear force is applied, as long as no external rotational force is present. This characteristic is essential to the vast majority of its uses. The tightening of a fastener's screw thread is comparable to driving a wedge into a gap until it sticks fast through friction and slight elastic deformation.

Threaded pipe

A threaded pipe is a pipe with screw-threaded ends for assembly.

Unified Thread Standard

The Unified Thread Standard (UTS) defines a standard thread form and series—along with allowances, tolerances, and designations—for screw threads commonly used in the United States and Canada. It is the main standard for bolts, nuts, and a wide variety of other threaded fasteners used in these countries. It has the same 60° profile as the ISO metric screw thread, but the characteristic dimensions of each UTS thread (outer diameter and pitch) were chosen as an inch fraction rather than a millimeter value. The UTS is currently controlled by ASME/ANSI in the United States.

ISO standards by standard number

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