What are drill bits?
A unibit (often called a step drill bit) is a roughly conical bit with a stairstep profile. Due to its design, a single bit can be used for drilling a wide range of hole sizes. Some bits come to a point and are thus self-starting. The larger-size bits have blunt tips and are used for hole enlarging.
Drill bits are generally classified as Twist Drill, Counterbore, Countersink, Flat Bottom Boring, and Specialty. On our web site we have divided these into two categories: Drill Bits - Normally used with hand held drills or drill presses fitted with standard chucks.
What are the best drill bits made of?
Black Oxide (Coating)
Black oxide is a coating over the steel drill bit to add corrosion resistance and reduce friction between the bit and workpiece. It’s a good general-purpose design that’s suitable for wood, softer metal, plastics, and composites that doesn’t cost an arm and a leg. The downsides are that they don’t stay sharp as long as some of the other twist bit options out there and you lose the benefits as the coating wears off the cutting edges.
When these bits go dull, you toss them. Also, don’t expect to cut through metal other than softer steels under 1/8-inch in thickness.
Titanium nitride is a coating you can use instead of black oxide that does the same job of resisting corrosion and friction. The added benefit comes from increasing the surface hardness and creating a thermal barrier that reduces heat buildup. The result is a drill bit that lasts longer than black oxide.
Titanium drill bits tend to drill faster than black oxide and chips move through the flutes better. One of the downsides is that the titanium nitride is just a coating and you lose the benefits as the coating wears off the cutting edges. Another is that you’ll need to pay more for these.
Titanium is a good choice for metal and wood-drilling. You’ll want to look elsewhere for concrete/masonry and you’re better off using your inexpensive black oxide bits for plastics and composites.
Cobalt (Steel Blend)
Cobalt drill bits are made from an alloy of 5% – 8% cobalt. Because the cobalt is part of the steel blend, its benefits run through the entire bit instead of wearing away like a coating. That characteristic also makes them an excellent candidate to sharpen rather than replace. With a much higher price tag than black oxide and titanium, you’ll want to go the sharpening route to save money.
Cobalt bits are capable of drilling through just about everything, though most Pros reserve them for metal drilling due to their cost. That’s a good move—you don’t want the one bit you own that’s able to drill through cast iron getting dull on everyday tasks that less expensive bits are perfectly capable of tackling.
Can you sharpen drill bits?
You can indeed sharpen most twist drill bits, and doing so not only keeps the bits more effective, it also increases the safety of your drill, as dull drill bits are likelier to slip or skid across hard materials.
There are electric drill-bit sharpeners available that make quick work of restoring the point to your twist bits. You can also tackle the job yourself with a bench grinder or a rotary tool with the appropriate grinding attachment. Another option is to use a metal sharpening file to do the job by hand.
Are drill bits universal?
As a general rule, various brands of drill bits can be used in any brand of drill, as long as the drill bits are sized to the drill’s chuck. The chuck is the part of the drill that clamps the bit in place. Common sizes of chucks are ¼-inch, ⅜-inch, and ½-inch. You cannot use a bit with a shank that is larger than your drill’s chuck.
How do you clean drill bits?
Keep your drill bits in tip-top shape by cleaning them whenever necessary. This task is easily accomplished by wiping the bit with a clean cloth after use—wait for the bit to cool down first—or for more stubborn grunge, using an old toothbrush to scrub away sawdust, drywall dust, or other caked materials.
If your drill bits are rusty, submerge them in a bath of white vinegar for at least 30 minutes, and then use an old toothbrush or a metal cleaning brush to scrub the rust away. Rinse the bit thoroughly in clean water and dry completely before using it or storing it.
What is a left-handed drill bit?
Most bits twist in a clockwise fashion towards the right. Left-handed bits, however, turn counterclockwise towards the left. These bits were originally designed back when power drills didn’t have reverse functions requiring nothing more than a flick of the switch to set— it was easier to use a left-handed bit rather than set the tool to reverse manually.
Today, left-handed bits are still sometimes used for removing bolts or other fasteners that have broken off inside the hole, making them very difficult to remove by hand. By drilling slightly into the broken fastener with a left-handed bit, you can often loosen the broken screw enough to pull it out and remove it.