One of Australia's most complex rail maintenance machines is working its way through  the southern highlands, leaving a shower of sparks in its wake.

Owned by QR National and on an 8 year $100 million contract to the Australian Rail Track Corporation, a Loram grinder is currently working in the Bundanoon area.

The grinder returns the rail head to its original profile, improving the ride and locomotive fuel efficiency, and reducing wear and tear on rolling stock.

The multi million dollar  grinding set  has 11 vehicles is more than 200 metres long,  and includes 5 grinding cars, each with 16 grinding heads.

It  comes complete with its own fuel storage system and a series of water tanks and spraying systems to suppress any fires which may be started by stray sparks.