Round Blades or Straight?
In any case, keep in mind that heat kills blades. Occasionally swing the oscillating tool blade back and forth out of the kerf to clean out dust. And don’t press so hard.
Faster Flooring Prep
Cut Rusty Faucet Nuts
But you may be able to pull off the impossible by using an oscillating saw tool equipped with a high-quality bimetal cutting blade.
Angle the tool against the nut and start it off at slow speed until it cuts a groove. Then increase the speed and keep sawing until you’re about three-quarters of the way through. Then break off the remaining portion with pliers.