Tengu format ruling
Drill Synchron

Card effect (current official text)If a Warrior-Type monster you control attacks a Defense Position monster, inflict piercing battle damage to your opponent. Once per turn, when you inflict battle damage to your opponent with this effect: You can draw 1 card.
Rulings
While you control this face-up card, during each battle between a Warrior Defense Position monster whose DEF is lower than the ATK of the attacking monster, inflict the difference as Battle Damage to your opponent. Once per turn, when you inflict battle damage to your opponent with this effect, you can draw 1 card.
- The effect to draw a card is a Trigger Effect that activates after damage calculation.
- The effect to draw a card will stack with effects like "Spiral SpIf you control 2 "Drill Synchrons" you can activate the effect of both of them when your WarriorDefense Position monster and inflicts damage.
Rulings data courtesy of Format Library — formatlibrary.com. Spotted an inaccuracy? Flag it in the Tengu forum — sourced change requests get reviewed.