While most of us understand the importance of properly maintaining power tools, drill bits deserve an equal amount of care. The first step is to buy products built to last. Consider speed, heat, vibration and material type in purchasing bits and keeping them in good shape. Understanding how these factors affect product life is crucial if you want to spend less money and do more with the tools you have.

The first consideration when selecting a drill bit is what type of material you will be drilling into.

If you’re drilling wood

• Brad point bits are an excellent choice for smaller holes. This drill bit looks much like a standard one, but the tip has a W-shaped center point that produces a clean hole upon exit. This prominent sharp point also aids the user in starting the hole exactly where they want and has less “walking” than a standard drill bit. It also can be used on a high-speed drill setting, resulting in a much quicker installation.
• Auger bits (also known as ship augers) are a better choice where larger and deeper holes are desired, or when you will be doing a considerable amount of drilling (such as installing NM cable through wood studs in a residence). This type of bit produces a clean hole at a moderate speed. The threaded tip means the bit is self-drilling once initial pressure has been applied, so the drill and drill bit do the work and the user doesn’t have to apply constant pressure. While expensive compared to other types of drill bits, proper care will ensure it lasts.
• Spade bits (also known as paddle bits) are the go-to choice where a larger but shallower hole is required. Compared to a standard round drill bit, a spade bit is flat and produces a round hole when rotated by the drill. It produces a rough, shallow hole at a high speed and is considerably less expensive than an auger bit. Since it’s flat, it needs less space for storage.
• Hybrid spade bits, or spade bits with an auger tip, have recently come on the market with advanced designs. These combine the speed and efficiency of a standard spade bit with the self-drilling capability of an auger bit, which is truly the best of both worlds. 

If you’re drilling metal

• Black oxide drill bits are made of high-speed steel (HSS) that has been heated to more than 900°F during the manufacturing process. This creates a black oxide finish that resists rust and corrosion. This finish also reduces friction between the bit and the drilled material. A black oxide bit is the least expensive of the three basic drill bits for metal and is good for routine use.
• Titanium-coated drill bits are HSS with a titanium nitride coating applied to them. This increases the hardness of the bit’s surface and reduces friction, which in turn results in increased production rates, greater corrosion resistance and a longer lifespan than a black oxide drill bit. As for cost, titanium-coated drill bits fall in the middle.

• Cobalt drill bits are HSS with a percentage of cobalt alloy. Unlike a titanium bit that has an exterior coating, a cobalt bit is alloyed throughout. The resulting material has a high resistance to the heat generated by drilling into highly abrasive and hard materials such as stainless steel, titanium and cast iron. Cobalt drill bits are the most expensive of the three types but, if cared for properly, tend to have the most longevity.

Hole saws

A hole saw is a good option that drills larger holes into thinner metallic objects. A hole saw is efficient because only the cutting edges contact the material. A simple metal disc is removed as opposed to a complete pile of metal shavings, as with standard drill bits.

• Standard bi-metal hole saws are good for drilling into thin metal. They are cost-effective, but the lower price sacrifices longevity. These saws tend to burn out quickly if they get too hot on a high-speed drill setting or are pressed into the material too forcefully.

• Carbide-tipped hole saws will generally last much longer. These hole saws have large tungsten carbide teeth attached to the cutting surface, similar to carbide-tipped circular saw blades. The carbide teeth can be resharpened, which can extend the saw’s life even further.

• Step bits are a popular choice among electricians for metal drilling. These solid, tapered bits increase in size the further they drill into the metal. The tapered design can eliminate the need to carry several loose drill bits within the same range.

If you’re drilling masonry

If you’re drilling masonry—concrete, brick, CMU, tile, etc.—there’s a bit for that. Masonry bits have a carbide tip attached to the drilling point that can withstand the hardness of the material being removed. They are made to withstand the impacts of such tools as hammer drills, which rely on impacting the masonry while spinning. Masonry bits can also be resharpened.

Drill bit use and care

Once you’ve selected your bit—depending on the material being drilled—you must consider the care throughout the bit’s lifespan. While drill bits are consumable items and not meant to last forever, there are a few things we can do to make them last longer.

Avoid letting your bits roll around and rust in the back of the truck. Before, during and after the drilling process, don’t let them come into forceful contact with another surface, and don’t drop them on the tips, which can ruin the cutting surface. Store your drill bits in a separate rigid container, by themselves, to help keep them from getting bent. Additionally, lightly oil drill bits once they cool down after use to prevent rust from forming.

Many people in the trades automatically assume that spinning a drill bit as fast as possible is best, but this is not always the case. The heat generated when drilling material, whether wood, metal or masonry, plays a huge role in the degradation of a drill bit. Most drill bits operate better with a lower speed and higher pressure. Consider using the lower speed setting on the drill and applying more downward pressure. This will result in less heat and a more accurate hole.

Using some type of cutting lubricant will also aid in keeping the drill bit cooler during the drilling process. Specific lubricants are available at most hardware stores. 

Using products such as WD-40 gel lubricant can add some advantages. Due to its composition, the gel tends to stay in place better compared to a completely liquid product. Additionally, the product can also be used to lubricate many tools with moving parts.

Consider vibration when trying to extend the life of a drill bit, as excessive vibration results in more heat and inaccurate, elongated holes. While slowing the drill down and using more pressure helps lower vibration, don’t exert too much pressure, as this may bend the bit. This is especially true of drill bits with smaller diameters, which bend more easily as there is less metal.

Many electricians prefer to use an impact-type drill as their drill motor, and there are bits specifically designed to withstand the rigors of an impact drill, such as Milwaukee Tool’s Shockwave line of bits. They are available in titanium-coated standard type as well as step bit and hole saw versions. As with any tool, always consult the manufacturer’s directions to ensure you are using them as intended.

Conclusion

As you can see, drill bit selection and use is much more than a one-size-fits-all scenario. Material composition must be considered, along with proper bit use and care. Collectively, these parameters will ensure that your drill bits last longer and cost you less (in dollars and aggravation) over time. 

Metcalf’s passion for passing on his knowledge has been an integral part of his 30+ year career. In addition to his work as a master electrician, he teaches numerous courses for Electrician U to help equip electricians with the skills they need to excel in their craft. To learn more about Electrician U, use this QR code or visit ElectricianU.com.

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