Best router bit for 1/2" acrylic?

[salth2owannabe]

I have an acrylic tank (1/2" acrylic) that has, what I would say, is very small access ports in the top of the tank, this thing is built like Fort Knox.
What I'm planning on doing is using a plunge router to open the top up a little, yet still leave plenty of top for strength. Anyone have an idea what style router bit (straight, flutes, spiral) might work best for this?
Thanks for the help!

[BeanAnimal]

Acrylics here at RC may have better recomendations...

But Spiral bits are my choice for such operations.

[salth2owannabe]

Thanks,
Any preference on up-cut, down-cut? Ever use the 0 flute spirals for plastics?

[BeanAnimal]

If you are going all the way through, UP or DOWN will work. UP bits work great for blind cuts. DOWN bits are great for keeping the workpiece clear of tailings.

[Acrylics]

salth2owannabe,
Any of the cutters will work fine, question is are you working off a template? How are you going to control the cut? If no template, might want to use a rabbett first to make the openings bigger a little at a time, then clean up with a pattern bit, this will also give you a larger radius in the corners which will help distribute stress.
FWIW, I wouldn't necessarily recommend plunge cutting through the acrylic.
As a generallity, I use a template, double face taped to the top of the tank and a spiral down-cut pattern bit for such operations. One could also use a template, double face taped to the underside of the top and a spiral up-cut flushcutter with good results.

HTH,
James

[salth2owannabe]

Thanks for the help guys,
I think I'm going to make a template out of 1/4 melamine and use a downcut spiral bit with a guide bushing. We'll see how it works.