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Instead of buying new drill bits when they eventually get dull, you can learn how to sharpen drill bits at home. While there are specialized tools that can help you shape the bit a little more easily, you can use a simple bench grinder or belt sander.
How To Sharpen Drill Bits
When you sharpen a drill bit, it is important to follow safety precautions. The number one piece of safety equipment for this procedure is a set of safety goggles. When you use a belt sander or bench grinder, the spinning motion can easily send sparks and spent material towards your eyes.
While we normally recommend wearing gloves when your hands get close to something that can hurt them, it may actually be safer to avoid gloves when sharpening drill bits. The extra loose fabric can get easily caught on the mounted rotational tool you are using to sharpen it, creating a likely hazard.
- Deburr your bits before sharpening. The stem and flutes can end up with burrs that, when you are holding the drill bit with bare hands, can move and cut you very easily.
- Hold the drill bit edge parallel to your grinder edge.
- Find an angle around 60 degrees from the tip to the edge.
- At that angle, move the bit until it contacts the grinder.
- Use light pressure against the grinder at first for around 5 seconds.
- Dip the bit in cold water to cool it down. It will heat up rapidly, and getting drill bits hot will decrease their life.
- Inspect your work and flip the bit 180 degrees so you perform the same action on the other side.
- Repeat the process, doing your best to keep the sides symmetrical. You want to end up with two even angles going to a central point that’s the same distance from both sides of the drill bit.
- When the ground edges look even and there are no more dull surfaces, test the drill bit with your hands on some scrap wood. If sharpened correctly, the bit will start to bite into the wood if you twist it straight in.
- Continue sharpening if necessary until the hand test starts to work.
- Finally, test your jobber drill bits in a drill: when used on wood, they should start cutting with only light pressure, and chips should fling away from the bit.
Tips and Tricks to Sharpen Drill Bits
There are many different ways to sharpen a drill bit, and we have explained the very basics of how to perform this. The step-by-step instructions above will get your drill bits sharp, yet there are some small changes you may use to get even more out of your sharpened bits.
First of all, it is important to know the different surfaces of the drill bit tip that matter when we are sharpening it, as there are conical shapes for step drill bits, and twisted shafts for standard ones.
- Lip: these are the main cutting edges. You will know them by the straight lines as you look straight down the tip of the bit.
- Landing: Also called the Land. It covers the backside of the lip for support and curves around.
- Chisel: The chisel pushes what you are trying to drill into the lip.
Round the Tip
The above method will create one flat surface on each side of the drill bit, but for many applications, we want a little more cutting power.
The area behind the lip of the drill bit is called the landing. This area maintains the stability of the lip and also creates an entry point at the apex of the two angles. When the landing is completely flat, it has a tendency to become uneven in its drilling and also provides less support for the lip.
To round out the landing, instead of evenly pressing drill bits into the grinder surface, you will slightly lift your rear hand up and down, leaving the hand closest to the grinder still. This should help you to create a rounded edge on the landing, and you can adjust it as you get more comfortable with the action.
Instead of making that trailing edge completely round, which can be difficult to keep symmetrical on both sides of the drill bit, you can create different stepped angles instead.
- Start the sharpening process as above, where you press it flat into the grinder, starting your first edge.
- Cut the two symmetrical faces into your bit.
- Start the process over again, but this time, hold the bit surface a little steeper so that it starts to grind down the heel.
- Continue on both sides until you have multiple stepped faces on the landing.
Measure for Symmetry
Drill bits work better when the two sides are symmetrical. If they are not, and especially if the point is off-center, your drilling will most likely drift off to one side. To avoid this, you may consider measuring your sharpening angles as you progress in the process.
There are two main tools you could reach for in this process.
A protractor is the best measuring tool for small angles. If you have an adjustable protractor and angle finder it will be the easiest to use since it fits over the angle, but a standard “D” shaped protractor would work as well.
Measure the lip angle using the protractor to be sure that you are staying consistent with the all-purpose 60 degrees per side. To be more thorough in your measuring, you may be able to find the manufacturer’s specs on the drill bit packaging or their website.
While the angle of sharpening is important to get the right clearance and balance between the two sides, measuring the length of the lip is also very effective to see if both sides are symmetrical. This can be difficult if you are sharpening small drill bits where you may need to go down to millimeters to get accurate measurements.
Measure from the point down to where the lip meets the edge of the drill bit on one side, then write it down. When it comes to smaller drill bits it is important to remember the length of the measurement, 1mm of a difference on a 1/8 inch bit can be the difference between a bit that cuts straight, and one that does not.
Use Different Grit Wheels or Belts
Some drill bits need more shaping and sharpening than others. For the bits that need a lot of material removed or evened out, you will want to start off with a coarse, lower grit surface to start your sharpening process. Low grit sandpaper and wheels can cut through metal bits in a hurry, so pay attention to how long you leave them on the grinder.
Once you have the main angles and shape, you can go to a finer, higher number of grit in order to sharpen the tip more smoothly. This will also give you better control when working on the lip area.
Use a Bench Grinder or Belt Sander
Both a bench grinder or a bench mounted belt sander work well to sharpen drill bits. If you have both available, we would recommend using the one you feel most comfortable with.
Be sure whichever tool you use for sharpening has a machine guard that is as close to the wheel as possible. Drill bits can get caught in that space if you are not careful.
- A bench grinder has a solid wheel so it will not give at all when you press a drill bit into it for sharpening.
- Belt sanders can produce a slight amount of give, creating a small rounding of the tip. We are looking for this anyway in most drill bit sharpening situations, so this may be considered a plus.
- If you know you are going to be using different grits in your sharpening process, you can have one tool set with the more coarse grinder, and the other with a finer grit to finish.
How To Tell When It Is Time To Sharpen Drill Bits
The easy answer to when a drill bit is dull is when it stops cutting through the material. If you have ended up at this state, your drill bit is far past the point when it should have been sharpened. Dull bits can cause rough hole edges, scorch marks, and may even jump off the material being drilled, causing injury.
- The chisel is not pushing into the material anymore.
- The lip is not sharp or has obvious rolling to it.
- The bit is not catching on the material, letting the drill speed up without much cutting power.
- The wood or other material may start to smoke as the chisel smears the material too much and the lip cannot cut it.
How to Keep Drill Bits Sharp
If you can keep your drill bits sharp, you will not have to worry about sharpening them as often. There are some precautions you can use to maintain all your tools, such as keeping them in a dry place, but some other rules apply to drill bits.
- The flutes, the open swirls around the body of the drill bit, need to be kept free of debris. If those start to pack down, the bit will heat up and will dull more quickly. When drilling deep holes, stop and remove the drill every ¾ inch or so and blow the debris out.
- Do not let the drill bit overheat. When drill bits heat up they become weaker, causing them to dull more quickly. Keep a cup or small bucket nearby with ice water in it, and dip your bit in it to cool off when drilling through hardened materials.
- It is difficult to sharpen hardened split drill bits using a grinder or belt sander. The “split” chisel that helps these bits cut so efficiently is very hard to sharpen in this manner. You will need some extra tools like diamond files or others.
- Use the correct type of drill bit for your project. Using the wrong drill bit can be catastrophic.
Sharpening a drill bit at home can be easy once you get the hang of it. The main things to concern yourself with are safety, keeping your sharpening angle consistent, and making sure the bit does not overheat. Also remember that since you are sharpening freehand, you have the freedom to shape the tip how you want.