Warning: Fiber disks hiding in your grinder bag will ruin your day

Picked up a 20 pack of what I thought were new flap discs at a garage sale outside Omaha. They looked fresh in the wrapper. First pour on a 30 foot driveway extension, that thing shredded in 40 seconds and threw chunks at my shins. Turns out they were old fiber reinforced disks someone had repackaged, they had been sitting in a damp shed for maybe 4 or 5 seasons. The resin was cooked from heat cycles in the garage. I finished the edges with a diamond cup wheel instead and it took twice as long. Now I check the lot number on every disc before I load it up, even from the big box store. Has anyone else gotten burned by stale abrasives that looked fine in the package?

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christopherh7929d ago

The lot number thing is smart, but I gotta point out one thing. Fiber discs and flap discs are totally different animals, and it sounds like you got sold fiber discs that were dressed up to look like flap discs. Fiber discs have that flat, stiff backing, while flap discs have the overlapping little flaps of sandpaper. If the resin on those old fiber discs was cooked from heat, they'd act exactly like you said, throwing chunks and shredding fast. That damp shed probably did more damage than the heat cycles honestly, moisture wrecks the bond between the grit and the backing. I check the date code on mine too now, but I also give them a little flex test before I even put one on the grinder. If it feels stiff or brittle instead of having a tiny bit of give, it goes straight in the trash.

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