Cylindrical pipe thread BSP (BSPP). Cylindrical pipe thread How to determine the pitch of an inch thread

MAIN DIMENSIONS
PIPE TAPER THREAD
(GOST 6211-81)

The standard applies to tapered pipe threads with a taper 1: 16 . used in conical threaded connections, as well as in connections of external conical threads with internal cylindrical threads with a profile in accordance with GOST 6357-81.

Taper 2tg(φ /2) = 1: 16;
φ = 3°34"48"; φ/2 = 1°47"24";
d and D are the outer diameters of the outer and internal threads s;
d 1 and D 1 - internal diameters of external and internal threads, respectively;
d 2 and D 2 - average diameters of external and internal threads, respectively;
P - thread pitch;
φ - cone angle; φ/2 - slope angle;
H - height of the original triangle;
H 1 - working height of the profile;
R - radius of curvature of the top and bottom of the thread;
C - cut of the tops and bottoms of the thread;
l 1- working thread length;
l 2- the length of the external thread from the end to the main plane.

dimensions, mm

Thread size designation	Step P	Number of steps per length 25.4 mm	H	H 1	C	R	Thread diameters in the main plane			Thread length
							d = D	d2 = D2	d 1 = D 1	l 1	l 2
1/16"	0,907	28	0,870935	0,580777	0,145079	0,124511	7,723	7,142	6,561	6,5	4,0
1/8"							9,728	9,147	8,566
1/4"	1,337	19	1,283837	0,856117	0,213860	0,183541	13,157	12,301	11,445	9,7	6,0
3/8"							16,662	15,806	14,950	10,1	6,4
1/2"	1,814	14	1,741870	1,161553	0,290158	0,249022	20,955	19,793	18,631	13,2	8,2
3/4"							26,441	25,279	24,117	14,5	9,5
1"	2,309	11	2,217187	1,478515	0,369336	0,316975	33,249	31,770	30,291	16,8	10,4
1 1/4"							41,910	40,431	38,952	19,1	12,7
1 1/2"							47,803	46,324	44,845
2"							59,614	58,135	56,656	23,4	15,9
2 1/2"							75,184	73,705	72,226	26,7	17,5
3"							87,884	86,405	84,926	29,8	20,6
3 1/2"							100,330	98,851	97,372	31,4	22,2
4"							113,030	111,551	110,072	35,8	25,4
5"							138,430	136,951	135,472	40,1	28,6
6"							163,830	162,351	160,872

DESIGNATION

The thread designation must include: letters (R - for tapered external threads, R c - for tapered internal threads, R p - for cylindrical internal threads) and a designation of the thread size:
external pipe conical thread - R 1 1/2
internal pipe conical thread - R with 1 1/2
internal pipe cylindrical thread - R p 1 1/2
left thread - R 1 1/2LH, R with 1 1/2LH, R p 1 1/2LH.

A threaded connection is designated by a fraction, for example Rc/R or Rp/R in the numerator of which the letter designation of the internal thread is indicated, and in the denominator - the external thread and the thread size.
For example: R with /R 1 1/4LH.

TOLERANCES OF PIPE TAPER THREAD
(GOST 6211-81)

dimensions, mm

Thread profile	Designation size threads	Offset of the main thread plane		Limit deviations diameter internal cylindrical threads
		±Δ 1 l 1	±Δ 2 l 2
	1/16"	0,9	1,1	±0.071
	1/8"
	1/4"	1,3	1,7	±0.104
	3/8"
	1/2"	1,8	2,3	±0.142
	3/4"
	1"	2,3	2,9	±0.180
	1 1/4"
	1 1/2"
	2"
	2 1/2"	3,5	3,5	±0.217
	3"
	3 1/2"
	4"
	5"
	6"
In the main plane, the average diameter has a nominal value.
Note. The maximum deviation ±Δ 1 l 1 and ±Δ 2 l 2 does not apply to threads with lengths shorter than those indicated in the first table.

Shorter thread lengths may be used.

Difference between actual sizes l 1 - l 2 must be no less than the difference in nominal sizes l 1 And l 2 indicated in the first table.

Related documents:

GOST 3469-91 - Microscopes. Lens thread. Dimensions
GOST 4608-81 - Metric thread. Preference fits
GOST 5359-77 - Eyepiece thread for optical instruments. Profile and dimensions
GOST 6042-83 - Edison round thread. Profiles, dimensions and limits
GOST 6111-52 - Conical inch thread with a profile angle of 60 degrees
GOST 6211-81 - Tapered pipe thread
GOST 6357-81 - Cylindrical pipe thread
GOST 8762-75 - Round thread with a diameter of 40 mm for gas masks and calibers for it. Main Dimensions
GOST 9000-81 - Metric threads for diameters less than 1 mm. Tolerances
GOST 9484-81 - Trapezoidal thread. Profiles
GOST 9562-81 - Single-start trapezoidal thread. Tolerances
GOST 9909-81 - Tapered thread of valves and gas cylinders
GOST 10177-82 - Persistent thread. Profile and main dimensions
GOST 11708-82 - Thread. Terms and definitions
GOST 11709-81 - Metric thread for plastic parts
GOST 13535-87 - Reinforced thrust thread 45 degrees
GOST 13536-68 - Round thread for sanitary fittings. Profile, main dimensions, tolerances
GOST 16093-2004 - Metric thread. Tolerances. Landings with clearance
GOST 16967-81 - Metric threads for instrument making. Diameters and pitches
GOST 24737-81: Single-start trapezoidal thread. Main Dimensions
GOST 24739-81 - Multi-start trapezoidal thread
GOST 25096-82 - Persistent thread. Tolerances
GOST 25229-82 - Metric tapered thread
GOST 28487-90: Conical locking threads for drill string elements. Profile. Dimensions. Tolerances

Straight pipe threads are mainly used for pipe connections, pipeline fittings and fittings. This thread covers diameters from 1/16 to 6" with the number of threads per 1" from 28 to 11.

The nominal diameter of a pipe thread is conventionally related to the internal diameter of the pipe. In terms of the ratio of pitches and diameters, pipe thread is a crushed inch thread according to OST 1260. Therefore, pipe thread at one time, before the standardization of small metric threads, was used not only for pipe connections, but also for fasteners, when there was a need to make threads with relatively in small steps, with large diameters. Pipe thread is a pan-European standard for pipes and pipe connections.

STRAIGHT PIPE THREAD DIMENSIONS
(GOST 6357-81)

The standard applies to cylindrical pipe threads used in cylindrical threaded connections, as well as in connections of internal cylindrical threads with external conical threads in accordance with GOST 6211-81.

Tolerances (according to GOST 6357-81) of the average thread diameter are established in two accuracy classes - A and B. Tolerances of the average thread diameter are total. Tolerances for diameters d 1 and D are not established.

dimensions, mm

Thread designation		Number of steps z at a length of 25.4 mm	Step P	Thread diameter			Working height of profile H 1	Curvature radius R	H	H/6
1st row	2nd row			outer d = D	average d 2 = D 2	internal d 1 = D 1
1/16" 1/8"	-	28	0,907	7,723	7,142	6,561	0,580777	0,124557	0,871165	0,145194
				9,728	9,147	8,566
1/4" 3/8"	-	19	1,337	13,157	12,301	11,445	0,856117	0,183603	1,284176	0,214029
				16,662	15,806	14,950
1/2"	5/8"	14	1,814	20,955	19,793	18,631	1,161553	0,249115	1,742331	0,290389
				22,911	21,749	20,587
				26,441	25,279	24,117
				30,201	29,039	27,877
1"	1 1/8" 1 3/4"	11	2,309	33,249	31,770	30,291	1,478515	0,317093	2,217774	0,369629
				37,897	36,418	34,939
				41,910	40,431	38,952
				44,323	42,844	41,365
				47,803	46,324	44,845
				53,746	52,267	50,788
				59,614	58,135	56,656
2 1/2" 3 1/2"	2 1/4" 3 3/4"			65,710	64,231	62,752
				75,184	73,705	72,226
				81,534	80,055	78,576
				87,884	86,405	84,926
				93,980	92,501	91,022
				100,330	98,851	97.372
				106,680	105,201	103,722
4"	4 1/2" 5 1/2"			113,030	111,551	110.072
				125,730	124,251	122,772
				138,430	136,951	135,472
				151,130	149,651	148,172
				163,830	162,351	160,872
When choosing thread sizes, row 1 should be preferred to row 2.

MAKE-UP LENGTHS according to GOST 6357-81

Make-up lengths are divided into two groups: normal N and long L.

dimensions, mm

Designation thread size	Step P	Make-up length
Designation thread size	Step P	N	L
1/16", 1/8"	0,907	St. 4 to 12	St. 12
1/4", 3/8"	1,337	St. 5 to 16	St. 16
1/2", 5/8"	1,814	St. 7 to 22	St. 22
1", 1 1/8", 1 1/4", 1 3/8"	2,309	St. 10 to 30	St. 30
1 1/2", 1 3/4", 2", 2 1/4", 2 1/2", 2 3/4", 3"		St. 12 to 36	St. 36
3 1/4", 3 1/2", 3 3/4", 4", 4 1/2", 5", 5 1/2", 6"		St. 13 to 40	St. 40
Numerical values of make-up lengths are established empirically.

The symbol for left-hand threads is supplemented with the letters LH.

Examples of symbols for threads of accuracy class A:

G 1 1/2-A
left-hand thread accuracy class B:

G 1 1/2 LH-B

The make-up length N is not indicated in the thread designation.
The make-up length L is indicated in millimeters.

G 1 1/2 LH-B-40

The fit is indicated by a fraction: the numerator of which indicates the designation of the accuracy class of the internal thread, and the denominator indicates the designation of the accuracy class of the external thread.

G 1 1/2-A/A; G 1 1/2 LH-A/B

The connection of an internal pipe cylindrical thread of accuracy class A according to this standard with an external pipe conical thread in accordance with GOST 6211-81 is designated as follows:

G/R 1 1/2 - A

P.S. At one time, the profile of cylindrical pipe threads (according to OST 266) extended to diameters up to 18" with the number of threads per 1" from 28 to 8.

1. PROFILE

1.1. The nominal profile of the pipe conical thread (external and internal) and the dimensions of its elements must correspond to those indicated in Figure 1 and Table 1.

Damn.1. Nominal profile of pipe tapered thread (external and internal) and dimensions of its elements

Taper ; ; ; - outer diameter of the external tapered thread; - internal diameter of external tapered thread; - average diameter of external tapered thread; - outer diameter of the internal tapered thread; - internal diameter of the internal tapered thread; - average diameter of the internal tapered thread; - thread pitch; - cone angle; - slope angle; - height of the original triangle; - working height of the profile; - radius of curvature of the top and bottom of the thread; - cutting off the tops and bottoms of the thread.

Table 1

Dimensions in millimeters


	Number of steps per length 25.4 mm

Note. The numerical values of the steps are determined from the ratio with rounding to the third decimal place and taken as the initial ones when calculating the main elements of the profile.

1.2. The dimensions of the internal cylindrical thread profile elements are in accordance with GOST 6357.

2. MAIN DIMENSIONS

2.1. The designation of thread size, steps and nominal values of the main dimensions of conical (external and internal) threads must correspond to those indicated in Figure 2 and Table 2.

Damn.2. Designation of thread size, steps and nominal values of the main sizes of tapered (external and internal) threads

Working thread length; - length of external thread from end to main plane

Table 2

Dimensions in millimeters


Designation thread size	Thread diameters in the main plane	Thread length

Shorter thread lengths may be used.

2.2. Numerical values of diameters and are calculated using the following formulas

The numerical values of the diameter are established empirically.

2.3. The difference between the actual dimensions must be no less than the difference between the nominal dimensions and indicated in Table 2.

2.4. The length of the internal tapered thread must be at least 0.8 (where - in accordance with Table 3)*.
________________
* The text of the document corresponds to the original. - Database manufacturer's note.

Table 3

Dimensions in millimeters


Thread size designation	Offset of the main thread plane	Limit deviations diameter of internal cylindrical thread





2; 3; 3; 4; 5; 6

Note. Maximum deviations do not apply to threads with lengths shorter than those indicated in Table 2.

2.5. The designation of thread sizes, pitches and nominal values of the outer, middle and inner diameters of the internal cylindrical thread must correspond to those indicated in Figure 3 and Table 2.

Damn.3. Designation of thread sizes, pitches and nominal values of outer, middle and inner diameters of internal cylindrical threads

2.6. The design of parts with internal threads (conical and cylindrical) must ensure screwing in external conical threads to a depth of at least .

3. TOLERANCES

3.1. The axial displacement of the main plane of the external and internal threads (Fig. 4) relative to the nominal location should not exceed the values specified in Table 3.

Damn.4. Axial displacement of the main plane of external and internal threads

Note. In the main plane, the average diameter has a nominal value.

The displacement of the main plane is total, including deviations of the average diameter, pitch, angle of inclination of the side of the profile and cone angle.

3.2. The maximum deviations of the average diameter of the internal cylindrical thread must correspond to those indicated in Table 3.

3.3. It is allowed to connect an external conical thread with an internal cylindrical thread of accuracy class A according to GOST 6357.

4. NOTATION

4.1. The thread designation must include: letters ( - for conical external threads, - for conical internal threads, - for cylindrical internal threads) and a designation of the thread size.

The symbol for left-hand threads is supplemented with the letters .

Examples of thread symbols:

- external pipe conical thread 1:

Internal pipe tapered thread 1:

Internal pipe straight thread 1:

Left hand thread:

4.2. A threaded connection is designated by a fraction, for example, or, the numerator of which indicates the letter designation of the internal thread, and the denominator - the external thread, and the thread size.

Examples of symbols for threaded connections:

- pipe conical thread (internal and external):

Internal pipe cylindrical thread (with tolerances according to this standard) and external pipe tapered thread:

Internal pipe cylindrical thread of accuracy class A according to GOST 6357 and external pipe conical thread:

APPENDIX (reference). LIMIT DEVIATIONS OF INDIVIDUAL THREAD PARAMETERS

APPLICATION
Information

1. This appendix contains information on the maximum deviations of individual thread parameters, which are the initial ones when designing a thread-forming tool and calculating thread gauges and are not subject to mandatory control, unless specifically stated.

2. The maximum deviations of the cut of the peaks and valleys (size), the angle of inclination of the side of the profile, the pitch and the cone angle (the difference in the average diameters along the length) of the conical thread are shown in Figure 1 and in the table.

Damn.1. Limit deviations of the cut of the peaks and valleys, the angle of inclination of the side of the profile, the pitch and the angle of the cone

es - upper deviation of the cut of the top and bottom of the external thread; ES - upper deviation of the cut of the top and bottom of the internal thread; ei - lower deviation of the cut of the top and bottom of the external thread; EI - lower deviation of the cut of the top and bottom of the internal thread; - tolerance of the angle of inclination of the side of the thread profile.

3. The maximum deviations of the cut of the peaks and valleys (size) of the internal cylindrical thread (Fig. 2) should not exceed:

- cut of vertices +0.05 mm (ES=+0.05 mm, EI=0);

- cut of depressions ±0.025 mm (ES=+0.025 mm, EI=-0.025 mm)

Damn.2. Limit deviations of cut of tops and bottoms of internal cylindrical threads

Dimensions in millimeters


Thread size designation	Prev. off			Average diameter difference thread length
			step on length
	peaks	depressions			Prev. off
					external thread	internal thread
					0,028 -0,014	0,014 -0,028
					0,042 -0,021	0,021 -0,042
					0,044 -0,022	0,022 -0,044
					0,058 -0,028	0,028 -0,058
					0,066 -0,034	0,034 -0,066
					0,073 -0,036	0,036 -0,073
					0,089 -0,045	0,045 -0,090
					0,111 -0,056	0,056 -0,111
					0,122 -0,062	0,062 -0,122
						0,073 -0,144
					0,155 -0,078	0,078 -0,155
					0,177 -0,089	0,089 -0,177
					0,200 -0,101	0,101 -0,200

Note. The value refers to the distances between threads. The actual deviation may have a minus or plus sign.

Electronic document text
prepared by Kodeks JSC and verified against:
official publication
Inch and special threads: Sat. GOST. -
M.: IPK Standards Publishing House, 2003

It would seem that there is something complicated in the pipes? Connect and twist... But, if you are not a plumber or an engineer with a specialized education, then you will definitely have questions for answers to which you will have to go wherever you look. And most likely the first thing they look at is the Internet)

We have previously talked about the diameters of metal pipes in this material. Today we will try to clarify the threaded connections of pipes for various purposes. We tried not to clutter the article with definitions. Basic terminology contains GOST 11708-82 which everyone can familiarize themselves with.

Pipe cylindrical thread. GOST 6357 - 81

Direction: Left

Accuracy class: Class A (increased), Class B (normal)

Why in inches?

The inch size came to us from Western colleagues, since the requirements of the current in the post-Soviet space GOST and are formulated on the basis of thread B.S.W.(British Standard Whitworth or Whitworth carving). Joseph Whitworth (1803 - 1887), a design engineer and inventor, demonstrated the screw profile of the same name for detachable connections back in 1841 and positioned it as a universal, reliable and convenient standard.

This type of thread is used both in the pipes themselves and in the elements of pipe connections: locknuts, couplings, elbows, tees ( see picture above). In the profile section we see an isosceles triangle with an angle of 55 degrees and roundings at the tops and bottoms of the contour, which are made for high tightness of the connection.

Threading of threaded connections is carried out on sizes up to 6”. All larger pipes are fixed by welding to ensure a reliable connection and prevent rupture.

Symbol in the international standard

International: G

Japan: PF

UK: BSPP

The letter G and the bore diameter (internal Ø) of the pipe are indicated in inches. The outer diameter of the thread itself is not included in the designation.

Example:

G 1/2- cylindrical external pipe thread, internal pipe Ø 1/2"". The outer diameter of the pipe will be 20.995 mm, the number of steps over a length of 25.4 mm will be 14.

The accuracy class (A, B) and the direction of turns (LH) can also be indicated.

For example:

G 1 ½ - B- cylindrical pipe thread, internal Ø 1 ½ inches, accuracy class B.

G1 ½ LH- B- cylindrical pipe thread, internal Ø 1 ½ inches, accuracy class B, left.

The make-up length is indicated by the last one in mm: G 1 ½ -B-40.

For internal pipe cylindrical threads, only the Ø of the pipe for which the hole is intended will be indicated.

Parallel Pipe Thread Size Chart

Thread size	Thread pitch, mm	Threads per inch	Thread diameters
	Thread pitch, mm	Threads per inch

How to determine the pitch of an inch thread

I’ll give you a picture from the English-language Internet that clearly demonstrates the technique. Pipe threads are characterized not by the size between the tops of the profile, but by the number of turns per 1 inch along the thread axis. A regular tape measure or ruler can help. Apply it, measure one inch (25.4 mm) and visually count the number of steps.

In the picture with an example ( see above) threads - from English these are literally “threads of thread”. In this case there are 18 of them. by one inch.

It’s even easier if you have a thread gauge for inch threads lying around in your tool box. It is very convenient to take measurements, but it must be remembered that inch threads may differ in the apex angle of 55° and 60°.

Tapered pipe threads

drawing of pipe tapered threads

Tapered pipe thread GOST 6211-81 (1st standard size)

Parameter Unit: Inch

Corresponds to the rounded profile of a cylindrical pipe thread with an angle of 55°. Cm. top part (I) of the three-dimensional image "drawing of pipe tapered threads".

Symbol

International: R

Japan: PT

UK: BSPT

The letter R and the nominal diameter Dy are indicated. The designation R means external thread, Rc internal, Rp internal cylindrical. By analogy with cylindrical pipe threads, LH is used for left-hand threads.

Examples:

R1 ½- external pipe thread, nominal diameter Dy = 1 ½ inches.

R1 ½ LH- external pipe thread, nominal diameter Dy = 1 ½ inches, left.

Conical inch thread GOST 6111 - 52 (2nd standard size)

Parameter Unit: Inch

Has a profile angle of 60°. Cm. lower part (II) of the three-dimensional image "drawing of pipe tapered threads". It is used in pipelines (fuel, water, air) of machines and machines with relatively low pressure. The use of this type of connection assumes tightness and locking of the thread without additional special means (linen threads, yarn with red lead).

Symbol

Example:K ½ GOST 6111 - 52

It stands for: inch conical thread with an outer and inner diameter in the main plane approximately equal to the outer and inner Ø of a cylindrical pipe thread G ½

Table of main parameters of tapered inch threads

Thread size designation (d, inches)	Number of threads per 1" n	Thread pitch S, mm	Thread length, mm		Outer thread diameter in the main plane d, mm
Thread size designation (d, inches)	Number of threads per 1" n	Thread pitch S, mm	Working l1	From the end of the pipe to the main plane l2	Outer thread diameter in the main plane d, mm
1/16	27	0,941	6,5	4,064	7,895
1/8	27	0,941	7,0	4,572	10,272
1/4	18	1,411	9,5	5,080	13,572
3/8	18	1,411	10,5	6,096	17,055
1/2	14	1,814	13,5	8,128	21 793
3/4	14	1,814	14,0	8,611	26,568
1	11 1/2	2,209	17,5	10,160	33,228
1 1/4	11 1/2	2,209	18,0	10,668	41,985
1 1/2	11 1/2	2,209	18,5	10,668	48,054
2	11 1/2	2,209	19,0	11,074	60,092

Metric tapered thread. GOST 25229 - 82

Parameter unit: mm

Produced on surfaces with a taper of 1:16

Used when connecting pipelines. The angle at the top of the coil is 60°. The main plane is shifted relative to the end ( see pic above).

Symbol

The letters MK are followed by an indication of the diameter in the main plane and the thread pitch in mm: MK 30x2

Metric Tapered Thread Size Chart

Thread diameter d for row		Step P	Thread diameter in the main plane
1	2		d = D	d2=D2	d1=D1	l	l1	l2
6	---	1	6,000	5,350	4,917	8	2,5	3
8	---		8,000	7,350	6,917
10	---		10,000	9,350	8,917
12	---	1,5	12,000	11,026	10,376	11	3,5	4
---	14		14,000	13,026	12,376
16	---		16,000	15,026	14,376
---	18		18,000	17,026	16,376
20	---		20,000	19,026	18,376
---	22		22,000	21,026	20,376
24	---		24,000	23,026	22,376
---	27	2	27,000	25,701	24,835	16	5	6
30	---		30,000	28,701	27,835
---	33		33,000	31,701	30,835
36	---		36,000	34,701	33,835

Characteristics of cylindrical pipe/inch threads relative to metric

The main characteristics of "inch" and "pipe" cylindrical threads in relation to "metric" threads for basic sizes.

Nominal thread diameter in dm	Inch thread		Pipe thread
Nominal thread diameter in dm	outer diameter, mm	number of threads per 1"	outer diameter, mm	number of threads per 1"

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	Item number
	Introductory part, 1.2, 3.3, 4.2

Cylindrical pipe thread BSP (BSPP). Cylindrical pipe thread How to determine the pitch of an inch thread

1. PROFILE

Damn.1. Nominal profile of pipe tapered thread (external and internal) and dimensions of its elements

2. MAIN DIMENSIONS

Damn.2. Designation of thread size, steps and nominal values ​​of the main sizes of tapered (external and internal) threads

Damn.3. Designation of thread sizes, pitches and nominal values ​​of outer, middle and inner diameters of internal cylindrical threads

3. TOLERANCES

Damn.4. Axial displacement of the main plane of external and internal threads

4. NOTATION

APPENDIX (reference). LIMIT DEVIATIONS OF INDIVIDUAL THREAD PARAMETERS

Damn.1. Limit deviations of the cut of the peaks and valleys, the angle of inclination of the side of the profile, the pitch and the angle of the cone

Damn.2. Limit deviations of cut of tops and bottoms of internal cylindrical threads

Pipe cylindrical thread. GOST 6357 - 81

Why in inches?

Symbol in the international standard

Parallel Pipe Thread Size Chart

How to determine the pitch of an inch thread

Tapered pipe threads

Tapered pipe thread GOST 6211-81 (1st standard size)

Symbol

Conical inch thread GOST 6111 - 52 (2nd standard size)

Symbol

Table of main parameters of tapered inch threads

Metric tapered thread. GOST 25229 - 82

Symbol

Metric Tapered Thread Size Chart

Characteristics of cylindrical pipe/inch threads relative to metric

Damn.2. Designation of thread size, steps and nominal values of the main sizes of tapered (external and internal) threads

Damn.3. Designation of thread sizes, pitches and nominal values of outer, middle and inner diameters of internal cylindrical threads