Just so there isn't any confusion, when I use an air-chisel on something like this, it isn't to do any cutting. It's to form a step and "push point" where quick bursts of the trigger can shock/vibrate/push the filter along in a circular motion.FWIW I went by the Charlotte NC dealer today. Asked to speak to a mechanic about the problem. Service Manager inquires why, I show pic, he says they've used an air chisel but when it's been done before they hit the threaded nipple and had to replace. Oooops. Should have persisted in speaking to a mechanic but they have one of those nice showroom kind of shops...
Because there is pressure on such a small part of the circle, 1/4" of movement would be a lot before the other side of the circle would have to be moved- to catch up.
OM