DIN EN 10226

Pipe thread for connections sealing in the thread

Tapered external threads and cylindrical internal threads

DIN EN 10226 has replaced the former DIN 2999. The thread dimensions comply with the international standard ISO 7/1. DIN EN 10226-3 applies to the new gauge system according to ISO 7/1.

This pipe thread is designed for a connection that seals in the thread. A suitable sealant (e.g. hemp or Teflon tape) can be used in the thread to ensure a tight connection.


Zylindrisches Innengewinde

cylindrical internal

thread marking: Rp



External thread conical or tapered
Labelling: R












hier in der Darstellung mit dem entsprechendem Lehrring

tapered male thread, marking: R




cylindrical internal thread, marking: Rp


The pipe thread DIN EN 10226 is also known as BSPT (British Standard Pipe Taper) Whitworth pipe thread.

DIN EN ISO 228-1

For connections not sealing in the thread

The DIN EN ISO 228 standard replaces the former Whitworth pipe thread standard DIN 259 (also known as BSPP - British Standard Pipe Parallel)

Cylindrical internal and cylindrical external thread. Marking: G

This pipe thread, for connections not sealed in the thread, is mainly used for the mechanical connection of fittings and valves. The connection is sealed by pressing two sealing surfaces outside the threads against each other and by inserting a suitable seal.


DIN EN 10226 vs. DIN ISO 228

The cylindrical internal Rp thread DIN EN 10226 has the same nominal dimensions for the thread diameter and thread profile as the cylindrical internal G thread to DIN ISO 228, but the internal G thread has only positive dimensions in the core and flank diameter (for DIN EN 10226 +/- tolerance). Therefore a DIN EN 10226 tapered external thread can be screwed into an ISO 228 G-cyl. internal thread, but the external thread can be screwed in approx. 1 thread turn further and, due to the large core diameter tolerance of the G-thread, there is a larger free space between the thread tips and thus a larger leakage path.

Never combine: cylindrical G male thread with Rp female thread, as the female thread may be too narrow.


NPT pipe thread

according to ASME/ANSI B1.20

The National Pipe Thread (NPT pipe thread) according to ASME/ANSI B1.20.1 is a US-American thread standard for self-sealing pipe fittings.

The internal thread as well as the external thread are tapered.

The tapered male NPT thread has the same core, flank and outside diameters at reference plane L1 as the female NPT thread at the start of the thread, so that it can be screwed in by hand up to this reference plane a. The power tightening by means of a tool increases the screw-in length and seals the screw connection with the aid of a suitable sealant (such as hemp or Teflon tape). Since both the internal and external threads are tapered, more threads contribute to sealing and force absorption. Due to the small thread flattening only a small leakage path is created.