We destroyed every grinding disc so you don't have to

The cheapest disc that beat discs costing five times as much. Won cost per inch removed, cost of removal rate, and cost of operating time. Lean on it hard: at light pressure it glazes at 8 minutes, at 8 lb on hot steel it pulled 22 inches and was still cutting at 20 minutes. Also in an extra-thick 11 mm version.

The exception to the pressure rule, and that makes it special. At just 4 lb on hot steel it removed 24 inches over 19 minutes, the best light-pressure number in the entire test. Thick and very aggressive, which makes it the pick for beveling and for lower-power battery grinders. Push too hard on cold steel and it smokes out at 4 minutes.

Nothing in the flap disc field removed steel faster: 20 inches in under 8 minutes at heavy pressure on a hot weld. The trade-off is that it's thin and heat-sensitive: at 11,000 RPM with 8 lb on cold steel it smoked out in 90 seconds. Run it on hot material with even pressure, or drop to 6,000 RPM when you need it to last.

The widest usable pressure range of anything we tested: it works at 4 lb, at 8 lb, at 11,000 RPM and at 6,000 RPM. Roughly 21 inches at heavy pressure, and a full 20-minute run removing 20 inches at reduced speed. It also never came apart, despite what the angry reviews claim. If you hand grinders to other people, buy this one.

The mid-price disc our crew keeps reaching for. It is unambiguous about what it wants: at 4 lb it glazed and quit after 5 minutes with 4 inches removed, and neither heat nor lower RPM helped. Switch to 8 lb and it turns into a different tool: 14 inches over 15 minutes, cold or hot. Heavy pressure, high speed, no exceptions.

The gentlest, best-balanced disc in the lineup, and the single most dramatic pressure story we recorded. At 4 lb it flatlined at 1.4 inches. At 8 lb it ran the full 20 minutes and removed over 11 inches cold, 13 inches hot. That 8× swing is exactly why its online reviews are split down the middle. Four grits, so you can stay on one system from hogging to finish.

The fastest material removal we measured, flap or fiber. 13 inches on a preheated coupon at just 4 lb, and 12 inches at 8 lb in half the time. It hogs a quarter inch like it's nothing. The catch: heat plus heavy pressure melts the abrasive into the backing. It smoked at 90 seconds under 8 lb on hot steel. Heavy even pressure on cold metal is its sweet spot.

When we plotted every disc in the study against cost, this one sat closest to the efficiency line. At 8 lb it removed nearly 20 inches cold and 22.5 inches on hot steel, and it was still going at 19 minutes. The star-shaped center keeps it flat against the pad instead of cupping. Give it light pressure and it glazes at 11 minutes. Don't.

A precision-shaped grain that only shows up when you give it heat and weight. At 4 lb it glazed and quit in about 3 minutes. At 8 lb on a preheated coupon it ran 14 minutes for 15 inches. Runs on the Combiclick quick-change system, so there's no center nut to get in the way. Available with the backing pad if you're starting from scratch.

Our test disc cost $4.20 and needed real pressure to earn it: 1 inch at 4 lb, but over 12 inches cold and 13 inches hot at 8 lb, running about 15 minutes. At our 25-pack price it lands under $3 a disc, which changes the math considerably. The Combiclick mount swaps discs in seconds and keeps the clamping nut out of your work.