Originally Posted By: Nick1994
Angle grinder with a cutting wheel. 30 seconds later (including time to turn it a few times on the vice) and it's open.
Yup, and a dremel with a cutoff wheel works too, as does a hack saw, but they all leave metal flakes behind.
The filter openers with the cutting wheels do not leave any debris behind.
I wish Harbor Freight still had the No.3 exhaust cutter, I read that it worked great for most all filter sizes and was cheap.