Pipe Threads where Pressuretight Joints are made on the Threads - ISO 7-1

ISO 7-1:1994 Pipe threads where pressure-tight joints are made on the threads

ISO 7-1 tapered threads are equivalent to DIN 2999, BS 21 (BS EN 10226-1), JIS B0203. Characteristics of ISO 7-1 tapered threads:

  • tapered thread 1o47'
  • truncation of roots and crests are rounded
  • 55o thread angle
  • pitch is measured in threads per inch

Note!

There is a distinction between

  • jointing threads - which are sealing piping threads for connections to ISO 7-1 and/or EN 10226-1
  • fastening threads - which are not sealing parallel threads for connections to EN ISO 228-1

The outside diameter of a pipe or fitting must be measured and compared to a table for size identification. A 3/4" ISO 7-1 pipe thread has an outside diameter - OD - of 1.060 inches. Each thread size has a defined number of threads per inch - TPI, or pitch. The 3/4" NPT pipe thread has 14 threads per inch. Both the TPI and OD of the thread are required for positive identification of thread size because more than one size have the same TPI.

ISO 7-1 Tapered Threads
Pipe Size
(inches)
Threads per Inch
TPI - pitch
Outside Diameter
OD
(inches)
Distance between threads
(inches)
1/16" 28 0.312" 0.036"
1/8" 28 0.402" 0.036"
1/4" 19 0.532" 0.053"
3/8" 19 0.677" 0.053"
1/2" 14 0.838" 0.071"
3/4" 14 1.060" 0.071"
1" 11 1.327" 0.091"
1-1/4" 11 1.669" 0.091"
1-1/2" 11 1.902" 0.091"
2" 11 2.374" 0.091"

ISO 7-1 threads may look similar to NPT threads. However, ISO and NPT threads should not be mixed. ISO threads have 55o taper angle versus 60o for NPT. The NPT root and crest configurations are also different from ISO. For ISO threads pitch is usually measured in millimeters ( may be expressed in Inch). The pitch are different.

Related Topics

  • Dimensions - Sizes and dimensions of pipes and tubes, and their fittings - inside and outside diameter, weight and more

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