I recently replaced an older, water-guzzling toilet with a low-flow model. The old toilet had been installed over a ceramic tile floor on a concrete slab, so I anticipated an easy swap. But one look at the rusted-out steel mounting rim on the ABS-plastic closet flange told me I had a bigger fish to fry. The old flange had to be cut off below slab level in order to sleeve in a solid PVC flange. No way was I going to break up the floor. Somehow, I had to cut the 3-inch drainpipe from the inside. A picture of a 2-inch-diameter circular saw blade on a long shaft formed in my head, but I didn't want to go chasing all over town hunting for parts. After building a plywood sled for my drill to control the cutting depth, I tightened a new 3-wing carbide-tipped slot-cutting router bit in my 1/2-inch drill and stuck it down the pipe. But within a few rotations, the bit rattled itself loose and went spinning down the drain. I fished it out again with a long snake and a magnet and moved on to Plan B.

After scouring three hardware stores without finding a suitable metal blade, I spotted a 2-inch abrasive cutting disc (The M.K. Morse Co., Canton, Ohio; 800/733-3377; www.mkmorse.com; $2.50) with a 3/8-inch arbor hole and recommended uses that included cutting plastic pipe. The proprietary arbor was too short (and too expensive for one-time use)...

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