I would use a small grinder with an ulta thin blade. Lubricate with a squeeze bottle using half water / half metho. Cut a few mm oversize , switch to a rubber pad and an 80 grit disc on the grinder. This will enable you to fair in to a perfect shape. No lubrication with the disc. Wear glasses ,ear plugs and gloves. The more the disc wears or clogs the better, finer cut. If you don't have anything , Bunnings or Trade Tools, Cheers, Bob

Thanks. The fitter at work thought a grinder blade would clog up and breakup. Not so?
Thanks for the gentlemens offer on the grinder Southace . I have a German made unit that will be fine if above issue is not a worry

It is generally not recommended to use a typical, thick grinder disc on aluminium - the soft metal will clog up the pores, thereby reducing the cutting action while increasing the heat in the disc.

However, the ultra-thin cutting discs (around 1mm and thinner) seem to be fine for cutting aluminium. Many of those discs actually print on the packaging that they are for use on Iron, Stainless and Aluminium. Those discs aren't porous and I would trust the manufacturers on this.

I like the look of Bob's advice - sounds like he's done a bit of work with aluminium.

Could use a circular saw if you can get a fine toothed metal blade. Easiest mothord os a jigsaw with a metal blade. The secret is to use a lube,keep rubbing the blade with cheap sunlight soap. HTH

Like I said I brought the new machine that has circular saw blades in it...one blade runs forward one runs reverse.....it's designed to cut metal up to 10mm has a auto wax feeder...and has very little kick back. I have cut 10 mm plate with jigsaw, grinder with thin cut disks and a circular saw! Nothing beats this new machine I think it's called a Ozsaw I will check next time I'm up at the car.

Multiblade for a 4" grinder, its really only a modified circular saw blade for grinders, quite cheap from bunnings or similar store, all our aluminium boat builders have them in their tool kit.