The Best Method For Sharpening Dull Drill Bits To Bring Them Back To Life

You can tell a dull drill bit more or less immediately. If you're drilling wood, you'll likely see thin wisps of smoke as it starts to burn. In masonry or metal, you'll get a lot of noise but hardly make a dent. The clever hack for drilling tile without cracking it won't work with a dull bit either. Fortunately, bringing your drill bits back to life takes minimal effort. 

Drill bits can be sharpened by hand or with a bench grinder, but the best method is using a dedicated machine like the Drill Doctor, available on Amazon for less than $60. These are simple to use yet very precise. The drill bit drops into a clamp that presents it to the internal grinding wheel at the perfect angle. A preset amount is automatically removed, and the drill bit is ready in moments. 

A bench grinder is a popular choice because it can also be used to sharpen your lawn mower blades, garden shears, and chisels. However, some people find bench grinders intimidating, with wheels spinning at several thousand rpm, and you need to be very careful to keep fingers well clear as there are no guards. Ryobi sells a reasonable one for $79 at Home Depot – more powerful options can sell from a few hundred to over $1,000. For those on a limited budget, sharpening drill bits by hand is also an option. All you need is a vise ($33 at Home Depot) and a flat file (less than $10 on Amazon). Give each of the upper faces four or five light strokes with the file, maintaining the existing tip angle.

How you sharpen your drill bits will depend on what type bit you have. When you're trying to choose the right drill bit, you may have noticed that several different materials are used. High-speed steel (HSS) is found in most standard twist drills used for wood, metal, and plastic, whereas cobalt is typically used for harder materials like cast iron or stainless steel. Tungsten-carbide tipped (TCT) and titanium nitride coated (TiN) drill bits are also popular.

HSS is hard-wearing, but other materials can be added to make the drill bits harder and longer-lasting. This has an impact on how they are sharpened or whether it is even possible. HSS and cobalt drill bits can be sharpened with a standard metal file or grinding wheel. TCT drill bits need either a file encrusted with industrial diamonds or a diamond grinding wheel. Don't worry, they're not as expensive as they sound! 

However, the material itself is not the only challenge. Construction is also important. HSS and cobalt drill bits are the same all the way through. They can be sharpened multiple times until they are too short to use. TCT drill bits, as the name suggests, have a hardened tip. This wears away each time it is sharpened. After three or four attempts, there will be nothing left so a replacement will be needed. Sharpening TiN drill bits is also difficult because the coating is thin. If they lose this coating, they are made of HSS underneath. Take this into consideration when sharpening different types of drill bits.