BAE Systems - Marine,Scotstoun, 'A' frame boring

Using two line boring set-ups to machine inboard and outboard propeller shaft ‘A’ bearing brackets simultaneously,Metalock Engineering UK has speeded up the procedure dramatically for Type 23 frigates at the Scotstounshipyard for BAE SYSTEMS Marine. Since introducing this procedure, Metalock has line-bored brackets onfive of the twin-screw frigates and two vessels for the Malaysian navy.

A predetermined datum was provided by the customer in the form of a taut piano wire from the centre of theengine drive shaft out through to the main ‘A’ bracket bore centre. The intermediate bracket(inboard) is about12 metres from the stern gland seal and the larger main bracket(outboard), 20 metres. Using that datum,Metalock set up their two line boring machines enabling both bores to be machined at the same time.

In the new forged/fabricated ‘A’ brackets there was 50mm of green material to be removed from each bore and40mm from each end face to give a length of 832mm for the intermediate bracket and 1658mm for the main.Finished bores were stepped to ease fitting of the bushes which were pulled into place. The intermediate stepsfrom 685mm to 686.5mm and the main had two steps from 685mm though 686.5mm to 688mm diameter.

Support brackets to accept Metalock’s boring bar assemblies were welded to the ‘A’ brackets. Four setsaccommodated drive and support facilities to machine two brackets at a time and on completion of the procedureon one side of the vessel, assemblies were moved to the remaining pair of ‘A’ brackets.

Using two line boring set ups to machine inboardand outboard propeller shaft bearing bracketssimultaneously, Metalock has speeded up theprocedure for Type 23 frigates at the Scotstounyard. HMS Portland shown.