Pipe threads: EN 10226-1 and EN ISO 228-1

Very often there are questions about the differences and the use of the two (most important) pipe thread types EN 10226-1 / ISO 7-1 and EN ISO 228-1.

For this reason a few explanations of these pipe threads are given below. (If you are looking for information on "dairy pipe threads" according to DIN 11851, please use the link to the corresponding page.)

Area of application

Pipe threads acc. EN 10226-1 / ISO 7-1 for thread sealing connections

The male thread is conical and seals when screwed into the cylindrical female thread. Hemp, teflon tape or sealing adhesive are used as sealing aids.

Tightness is achieved by a metallic connection between the thread flanks of the conical male thread and the cylindrical female thread, which is optimized by sealing aids. The production of the threaded connection requires know-how and practice.

Due to the large tolerances of the two threads, the screw-in depth can vary greatly. When combining external threads at the lower tolerance limit and internal threads at the upper tolerance limit, please do not produce the "missing" screw-in depth by increasing screw-in forces!

EN 10226-1 replaces the former DIN 2999, BS 21, ...

Pipe threads acc. EN ISO 228-1 for connections that do not seal in the thread ("fastening thread").

The tightness can only be produced by flat gaskets or O-rings.

In the meantime, the thread connection can also be made with special sealing adhesives for smaller diameters - but this was never the aim of this pipe thread standard for fastening threads!

EN ISO 228-1 replaces the former DIN 256.

KVT-QV-mit-Aussengewinde
KVT-QV-220

Pipe thread characteristics

The following table shows the (current) designations of the two thread types.

  EN 10226-1
 EN ISO 228-1
  "Connection thread" "Fastening thread"
  Female thread Male thread Female thread Male thread
  cylindircal cnical cylindircal cylindircal
Designation Rp 1" R 1" G 1" G 1"

Note: The male thread DIN ISO 228-1 can be manufactured in two tolerance classes (A and B).

What threads are produced at KVT?

Die KVT GmbH fertigt in der Regel alle Innengewinde und alle Außengewinde, die für den Anschluss von Rohren gedacht sind, entsprechend DIN EN 10226-1. Falls Sie Gewinde nach EN ISO 228-1 benötigen sollten, fragen Sie bitte an!

Can threads according to DIN EN 10226-1 and DIN ISO 228-1 be connected with each other?

Without special measures: No!

Screwing a cylindrical male thread according to EN 228 ("G") into a cylindrical female thread according to EN 10226 ("Rp") only works if the tolerance field of the male thread is restricted. This is done by some fitting manufacturers.

However, this connection does not result in a sealing connection unless special measures are taken.

DIN EN 10226-1: Pipe threads where pressure tight joints are made on the threads - Part 1: Taper external threads and parallel internal threads - Dimensions, tolerances and designation)

Nominal

thread

size

 Number
of pitches
on
25.4 mm		 Pitch Thread-profile height Outside diameter knife
(in the test plane) d = D		 Medium screw-in Usable thread length for nominal test length min.
    mm mm mm mm mm
1/16 28 0,907 0,581 7,723 2,5 6,5
1/8 28 0,907 0,581 9,728 2,5 6,5
1/4 19 1,337 0,856 13,157 3,7 9,7
3/8 19 1,337 0,856 16,662 3,7 10,1
1/2 14 1,814 1,162 20,955 5 13,2
3/4 14 1,814 1,162 26,441 5 14,5
1 11 2,309 1,479 33,249 6,4 16,8
1 1/4 11 2,309 1,479 41,91 6,4 19,1
1 1/2 11 2,309 1,479 47,803 6,4 19,1
2 11 2,309 1,479 59,614 7,5 23,4
2 1/2 11 2,309 1,479 75,184 14 26,7
3 11 2,309 1,479 87,884 17,1 29,8
4 11 2,309 1,479 113,03 21,9 35,8
5 11 2,309 1,479 138,43 25,1 40,1
6 11 2,309 1,479 163,83 25,1 40,1

DIN EN ISO 228-1:Pipe threads where pressure-tight joints are not made on the threads - Part 1: Dimensions, tolerances and designation (ISO 228-1:2000); German version EN ISO 228-1)

Dimensions for external threads DIN EN ISO 228-1:

  Outside-
diameter
d		 Flank diameter
d2

Nominal
thread
size

d max

d min

d2 max

d2 min
Tolerance
class A

d2 min
Tolerance
class B
1/16 7,723 7,509 7,142 7,035 6,928
1/8 9,728 9,514 9,147 9,04 8,933
1/4 13,157 12,907 12,301 12,176 12,051
3/8 16,662 16,412 15,806 15,681 15,556
1/2 20,955 20,671 19,793 19,651 19,509
5/8 22,911 22,627 21,749 21,607 21,465
3/4 26,441 26,157 25,279 25,137 24,995
7/8 30,201 29,917 29,039 28,897 28,755
1 33,249 32,889 31,77 31,59 31,41
1 1/8 37,897 37,537 36,418 36,238 36,058
1 1/4 41,91 41,55 40,431 40,251 40,071
1 1/2 47,803 47,443 46,324 46,144 45,964
1 3/4 53,746 53,386 52,267 52,087 51,907
2 59,614 59,254 58,135 57,955 57,775
2 1/4 65,71 65,276 64,231 64,014 63,797
2 1/2 75,184 74,75 73,705 73,488 73,271
2 3/4 81,534 81,1 80,055 79,838 79,621
3 87,884 87,45 86,405 86,188 85,971
3 1/2 100,33 99,896 98,851 98,634 98,417
4 113,03 112,596 111,551 111,334 111,117
4 1/2 125,73 125,296 124,251 124,034 123,817
5 138,43 137,996 136,951 136,734 136,517
5 1/2 151,13 150,696 149,651 149,434 149,217
6 163,83 163,396 162,351 162,134 161,917

 

Dimensions for internal threads DIN EN ISO 228-1:

  Flank diameter D2   Bore
diameter D1		  
Nominal thread size

D2 min

D2 max

D1 min

D1 max
1/16 7,142 7,249 6,561 6,843
1/8 9,147 9,254 8,566 8,848
1/4 12,301 12,426 11,445 11,89
3/8 15,806 15,931 14,95 15,395
1/2 19,793 19,935 18,631 19,172
5/8 21,749 21,891 20,587 21,128
3/4 25,279 25,421 24,117 24,658
7/8 29,039 29,181 27,877 28,418
1 31,77 31,95 30,291 30,931
1 1/8 36,418 36,598 34,939 35,579
1 1/4 40,431 40,611 38,952 39,592
1 1/2 46,324 46,504 44,845 45,485
1 3/4 52,267 52,447 50,788 51,428
2 58,135 58,315 56,656 57,296
2 1/4 64,231 64,448 62,752 63,392
2 1/2 73,705 73,922 72,226 72,866
2 3/4 80,055 80,272 78,576 79,216
3 86,405 86,622 84,926 85,566
3 1/2 98,851 99,068 97,372 98,012
4 111,551 111,768 110,072 110,712
4 1/2 124,251 124,468 122,772 123,412
5 136,951 137,168 135,472 136,112
5 1/2 149,651 149,868 148,172 148,812
6 162,351 162,568 160,872 161,512

How to measure pipe threads?

  • The measurement of pipe threads is complicated by the fact that the measurement in inches refers to the inside diameter of the pipe.
  • For this reason, we have created a pipe thread ruler that makes it very easy to distinguish between the different threads.
  • Instructions for measuring with the pipe thread ruler.
Rohrgewindelineal-Rueckseite-2024-09-02

Links for more informations about threads:

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