i boughta turboxs rfl and in the instrucitons it says that i need to drill a 1.25" hole for the flange. my piping is made of aluminum, whats the best way to make a 1.25" hole? the biggest drill bit i have is .5".

 

they sell metal hole saw at shops, i got mine from a local weldings supply store, they have various sizes.

 

ho saw you can get them at any hardware store or home depot, sears, etc..