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In a professional workshop or on a job site, there is no such thing as a "universal" drill bit. Using the wrong geometry or material composition isn't just inefficient; it is a fast track to broken tools, damaged workpieces, and wasted time. Whether you are boring through hardened steel or sinking fasteners into masonry, understanding the science of the bit is what separates the hobbyist from the pro.
Pro-grade bits are defined by their point angle and flute design.
The 118° Point Angle: This is the industry standard for general-purpose drilling in wood and mild steel. It allows for a controlled cut without excessive pressure.
The 135° Split Point: This is what pros look for in metal bits. The "split" creates a self-centering action, meaning the bit won’t "skate" across the surface when you pull the trigger. If you are drilling into stainless steel or thick angle iron, look for this specifically.
HSS (High-Speed Steel): Ideal for wood and plastics. They are tough and inexpensive but lose their edge quickly when exposed to the high heat of metal drilling.
Cobalt (M35/M42): These contain 5–8% cobalt. They are designed to retain their hardness even when they get extremely hot. Pro Tip: Use these for stainless steel or cast iron, but be warned—they are brittle and will shatter if you use them in a drill press at an angle.
Carbide-Tipped: The absolute standard for masonry. The carbide insert is much harder than the steel body, designed to withstand the percussive forces of hammer drilling.
Coatings are not just for color; they significantly change the performance of the tool.
Black Oxide: Provides heat resistance and lubricity. Great for general-purpose HSS bits.
Titanium Nitride (TiN): A gold-colored coating that increases surface hardness and reduces friction, allowing for much higher drilling speeds.
Cobalt (Uncoated): Often bronze in color, these are designed for the toughest materials where you need maximum heat resistance.
The Feed and Speed Rule: Smaller holes require higher RPMs; larger holes require lower RPMs. If you are burning the wood or smoking the metal, your RPM is too high, or your feed rate (downward pressure) is too low.
Clearing the Flutes: In deep-hole drilling, "peck" drilling is essential. Drill a few millimeters, pull the bit out to clear the shavings, then go back in. Clogged flutes generate friction, which is the #1 cause of bit failure.
The Pilot Hole Hierarchy: Never skip a pilot hole on finished timber. A pilot hole should be roughly the diameter of the core of the screw (excluding the threads). This prevents the wood from "splitting" due to hydraulic pressure as the screw enters.
Q: I’m working with stainless steel and my bits are dulling instantly. What am I doing wrong? A: Stainless steel "work hardens." If you drill slowly and apply light pressure, you are actually making the steel harder. You need a Cobalt bit, plenty of cutting fluid, and firm, consistent pressure. Do not let the bit rub; it must be cutting constantly.
Q: Why do my masonry bits seem to "drift" when I start a hole? A: Starting on a hard surface is difficult. Use a center punch to create a small dimple in the masonry before you begin, or start on the "Rotary" setting (no hammer) until you have a small pilot, then switch to "Hammer" mode.
Q: Are hex-shank bits just for impact drivers? A: Yes, they are designed for the high-torque, "impact" action of an impact driver. Do not use them in a standard drill press; the hex shank lacks the surface area of a round shank and will eventually deform your chuck.
Q: What is the "Step Drill" (Unibit) hype about? A: A Step Drill is a lifesaver for electricians and sheet metal workers. One bit can drill holes from 4mm up to 20mm, and it automatically deburrs the hole as it passes through. It saves you from carrying ten different bits.
