PN Nuts help the Royal Navy set a new course for future serviceability

Pilgrim Admin


When the UK’s S and T class of Nuclear defence submarines underwent major upgrade work to improve maintainability with some feature benefits also included in the latest Astute class of boat.

Rudder blades, for example, have been removed every eight years as part of the rolling maintenance programme, however problems where encountered due to corrosion of the conventional fixing systems securing the bladed to the shaft. Salt water environments are known for accelerated corrosion of metal parts and in the case of the upper rudder blade assembly which spend time both submerged and above water level when the boat is surfaced.

A new upgraded rudder was designed requiring a fixing technique to ensure securing of the rudder on a keyless Morse taper shaft. The installation requires considerable load to drive the blades into position.


The solution designed was the Pilgrim PN Nut along with the Pilgrim Oil Injection System as the best solution to provide the load and control required to set the rudder and hydroplane blades onto the taper shaft.

As important when the nut is reversed and pressurised simultaneously with oil injection to the taper interface  it will reliably and without damage remove the blades quickly and easily.


  • Easy to install and remove.
  • Safe.
  • Corrosion resistant solution.