Ans: A bench grinder with a 6-inch diameter is designed for DIYers for multi-functional usage (like to sharpen, grind, polish and repair various gears). While an 8-inch diameter grinder is meant to use for professionals who perform complicated grinding tasks/applications. Though the 8-inch bench grinder wheel runs slower, it needs fewer wheel changes than a 6-inch grinder, which means 8-inch require less maintenance, yet expensive than 6-inch models.