Fractional vs Metric Drill Bits: How to Choose and Convert Between Systems
Most US hardware stores sell drill bits in fractional inch sizes (1/4″, 3/8″, 1/2″), but imported hardware, metric fasteners, and European equipment use millimeter sizes (6mm, 8mm, 10mm). Knowing which system to use  and how to convert when you need a close match  saves trips to the store and prevents the frustration of …