Gear Grind is a physical Steel attack that hits its target twice. If the first strike break a Substitute, it will hit the opponent directly. Bide and Counter only count the second hit. Contact Abilities and Focus Band trigger on each strike as well as Weak Armor and Rocky Helmet. Focus Sash holders and Pokémon with Sturdy activate only on the first strike meaning the attack could faint the opponent regardless.
BWB2W2 - The user attacks by throwing two steel gears at its target.
XYORAS - The user attacks by throwing steel gears at its target twice.