[3][4] The company was established in 1942,[5] and is a branch of the Haden MacLellan engineering group.
[3] Prior to this the company was a part of B Elliott, which sold Philidas to Haden MacLellan in 2000.
[9] A Philidas nut[5] is a locknut with one or more slots cut laterally in the reduced-diameter circular top[10] for less than half the diameter, the metal above the slot(s) being deformed downwards so that over the last one or two turns, the thread for half the diameter is "axially depitched" or displaced from its normal position.
As the nut is threaded on, the displaced sections are elastically forced back axially to their original position, the load increasing the friction between the nut and the fastener, creating the locking action.
These nuts retain their locking action at temperatures limited only by the base material, as no polymeric insert is used, and as the locking action is by elastic deformation, they can be re-used multiple times.