Full cutting ring assembly in hardened assembly stud (VOMNW…)



  • This instruction describes the complete assembly of a cutting ring (SRD) on the pipe in an assembly stud (VOMNW…). This is not a pre-assembly!



  • Lightly oil the thread and cone of the assembly stud aswell as the tube end and the thread of the union nut.
  • Slide the union nut and cutting ring onto the pipe, making sure that the cutting ring is in the correct position; the cutting edges of the cutting ring must face towards the end of the pipe, otherwise assembly will be incorrect.


Cutting ring assembly

  • Tighten the union nut until the force required to turn it* increases noticeably; at the same time, push the pipe firmly against the limit stop in the assembly stud, otherwise the pipe will not be cut properly. The pipe must not be allowed to turn during assembly.
  • Tighten union nut 1 ½  turns with the spanner.



  • Disassemble the pipe or threaded connection and check that a clearly visible shoulder of cut material is present in front of the first (front) cutting edge. In this case, the cutting ring may be allowed to rotate, but must not move axially.



  • Oil the threads of the union nut and the screw sleeve. Thread the union nut onto the screw fitting until the force required to turn it* increases noticeably. Turn the union nut of the threaded connection or pipe about 30° to 60° further with the spanner (tighten/tighten fully).

The cones of the assembly stud are subject to normal wear and must be checked at regular intervals with taper gauges.

* Definition of „noticeably increased force“:
Tighten the union nut until the point at which it becomes noticeably more difficult to turn the union nut. At this point, for example, minor damage on the thread caused by the union nut getting caught must be overcome.
With sealing cone screw-on fittings with O-Ring (AOL / AOS), the pre-stressing of the O-Ring must be bridged and the sealing cone must lie metallically flush against the cone of the HL/HS connector.