Picking out the right drill can be challenging for novices like myself, especially when you take into account the material, flutes, coatings, point styles, tolerances, length, and other factors. But one of the first hang ups I encounter are the different types of sizes – letter sizes (A-Z), wire gauge (#s), fractional sizes (inches), and metric sizes (mm). My knee jerk reaction is to buy a handful about the size I need, labels aside. What’s with all these different systems anyway? Aren’t they just the same tool called a bunch of different names? Here’s what I learned.

The most important measuring tools from Tormach.

For those that just can’t put a square peg in a round hole, there’s rotary broaching – a milling method that produces a hexagonal or other polygonal holes. First, a pilot hole is drilled into the work piece, followed by a chamfer at the top – chamfering is not necessary, but for a better quality broach, it is highly recommended.