Adjust a slicer to thinnest setting (1/16 or 1/32 in.) and place over a large bowl of cold water. Using the safety guard, slice russet or Yukon Gold potatoes (peeled or scrubbed) into water. Let soak 10 minutes; rinse slices and blot completely dry with paper towels.
Heat 2 inches of vegetable oil in a 4- to 5-quart pan over medium-high heat to 380°. Fry potatoes in batches (do not overcrowd pan), stirring occasionally to separate and submerge slices, until crisp and golden, 1 1/2 to 2 minutes for 1/32-inch-thick slices, 3 1/2 to 4 1/2 minutes for 1/16-inch-thick slices. Using a slotted spoon, transfer to paper towels to drain. Let oil return to 380° between batches.
Sprinkle with salt and fresh-ground pepper.