Tool review: Sanding Discs
We reduced 2 cubic feet of poplar to dust -- literally -- to find the top-performing abrasives for your random-orbit sander.
The best abrasives start fast, then last and last
Most hook-and-loop sanding discs look alike except for their color, so how can you tell which ones give the best value? You can't unless you test 'em, so that's what we did with 15 popular brands. Here's what we learned.
To quantify the aggressiveness and durability of the discs, we sanded a single poplar board with 100- or 120-grit abrasive (depending on what the maker offers) for 15 minutes with each disc, weighing the board after every minute. A 1-pound weight affixed atop the sander provided consistent downward pressure. Then, we repeated the test with two more discs of each brand and averaged the results. (That's more than 11 hours of sanding for those of you keeping track at home.)
This chart shows the results of that test. In the first minute, Craftsman Professional, Klingspor Stearate, Norton 3X, and Bosch came strong out of the gate when the abrasives were factory-sharp. But by the end of the first five minutes, Bosch had slipped to the middle of the pack.
In the second five-minute interval, all of the discs removed less wood than in the first five minutes as they began to dull or load with dust. Again, Klingspor Stearate's performance fell off the least -- only 11 percent. And during the final five minutes, most discs leveled off, removing 3-10 percent less than in the middle five minutes. Bottom line: The top discs abraded more wood in their first five minutes than the Ace Hardware discs did in 15.
But is an aggressive, durable disc a good value? That depends on the price of the disc. When purchased in a box of 50 at the time of our test, Klingspor Stearate costs about 25 cents for every gram of wood removed if you used the disc for 10 minutes, making it a terrific value compared to the similar-performing Craftsman Professional discs at $1.10 per gram of wood removed. Bosch Standard, Mirka Gold, Gator Ultra Power, and Makita also provide above-average value at 43-58 cents per gram removed. (Discs sold in packages of 15 or fewer discs tend to have the highest cost-per-gram.)
Starting with 100- or 120-grit discs, we sanded pine boards with equal strokes through each grit up to 220 (or 240 for brands without 220-grit discs), then applied stain to each sample to show any scratching left behind. Most of the discs left only minor scratching visible to the naked eye after the highest grit, although Gator's Ultra Power left more prominent scratches. (See photo.)
We were pleased to see that a handful of 180-grit discs -- Bosch, Gator Power, Makita, Mirka Abranet, and Norton 3X and MultiAir -- delivered a near scratch-free finish that would be acceptable to all but the fussiest of woodworkers. These discs save you time by not having to sand to a higher grit.
Dust collection. We observed better-than-typical dust collection from two distinctly designed discs, shown at right: Mirka's Abranet and Norton's MultiAir. These holes-everywhere configurations allow fine sanding dust to migrate to the sander's vacuum holes through the hook-and-loop backing. (We could see the dust path on the back of the discs after use.) If you're particularly sensitive to dust, these discs may be worth the extra money.
Grit readability. If you forget which disc grit is on the sander, you should be able to peel it back and read the grit markings on the back. On the Craftsman Professional and both Norton discs, dark print against a dark blue background (photo) made reading the disc label a challenge.