Sharpen Your Drill Bits





Introduction: Sharpen Your Drill Bits

About: I miss the days when magazines like Popular Mechanics had all sorts of DIY projects for making and repairing just about everything. I am enjoying posting things I have learned and done since I got my first ...

Sharp drill bits are fun to use. They work so well. Dull bits are dangerous. They can break. One broke for me once and went through my thumbnail and out the other side of my thumb.

Step 1: A Dull Bit and a Sharp Bit

The bit on the left is a little dull. Notice the glint of light on the cutting edge between the two flutes. Compare that with the crisp edge on the freshly sharpened bit on the right.

Step 2: My Favorite Sharpening Tool

People who know what they are doing can sharpen bits by hand. In theory, hold the bit with the shank angled off to the left at about 59 degrees. As the bit contacts the grinding wheel, simultaneously move the shank farther left and downward while twisting it clockwise. I have tried, but I have never been able to make it work for me.

I bought this bit sharpening tool almost 30 years ago for less than $20. The same tool is still available at Amazon and other places, and it is still less than $20.

A Drill Doctor is a very nice tool, but it costs four or five times the cost of this tool. I do not sharpen bits often enough to justify the cost of a Drill Doctor.

Step 3: Set to 59 Degrees

This sharpening guide can accept drill bits with several different profiles. My bits have a 59 degree profile on the cutting edge. Set the tool to 59 degrees and tighten the thumbnut.

Step 4: Catch the Edge

The tool has a small tip and the edges of the bit's flutes rest against it. You may have to raise or lower the tip so it fits against the flute edges properly.

Step 5: How Much Overhang

As a starting point make the overhang (space between the yellow lines) equal to the radius of the bit (space between the green lines). See the next step for why it matters.

Step 6: Width and Angle of the Cutting Edge

Notice the angle of the red line. If there is too much overhang in the previous step, the red line will approximate the cutting edge at the tip of the bit. It is too wide and the bit profile will be too flat. The bit will skate on a metal surface and the hole will be hard to start. You can reduce the bit's overhang quite a bit, but be careful. If you reduce it too much, the tip you adjusted in step 4 may come into contact with the grinding wheel and you will damage your sharpening guide.

Step 7: Ideal Cutting Edge Angle

The ideal is to have the shortest cutting edge possible. This would be a cutting edge that runs between the low points in the valleys of the fluting. See the yellow line. This bit is close to ideal and will cut steel very well.

Step 8: Clamp the Bit in the Tool

When you have the overhang set, turn down the screw that clamps the bit in the tool's trough.

Step 9: Set the Tool for Bit Length

Set the sharpening guide for the length of the bit you want to sharpen. Keep the end of the bit in the moveable trough, not hanging in the air. Loosen the metal colored nut. Adjust the black nut. Tighten the metal colored nut.

Step 10: Align for Height

The end of the bit should be squarely aligned with the grinding wheel. I use a radial arm saw for my grinding. The tip of the bit should be even with the center of the motor shaft.

Step 11: Clamp the Tool to the Table

You want the bit to kiss the grinding wheel while sharpening it. If the bit is too close to the grinding wheel; sharpening will be difficult, the bit will become too hot, and you will remove a lot more material than necessary.

Keep the base of the sharpening guide square to the surface of the grinding stone (green lines), but turn the upper portion of the guide so the tip of the drill bit is just a little to the left of the center (angle between long green line and the yellow line). Slide the guide forward so the bit lightly touches the grinding wheel's surface. Clamp the guide to the table.

Step 12: Get Ready to Grind the Bit

Swing the tip of the bit to the right. Start the motor.

Step 13: Grind

Swing the rear of the sharpening guide to the right (red arrow) so the tip of the bit moves into the wheel. The yellow shower of sparks is added in a photo editing program, but the actual grinding happens when the bit is in about this position.

Step 14: Rotate the Bit One-half Turn

Continue swinging the guide until the tip of the bit is beyond the cutting wheel. You need to rotate the bit one-half turn and repeat the process in order to sharpen the other half of the bit.

It is safer to turn the motor off and wait for the wheel to stop. Loosen the hold down on the bit and turn the bit one half turn. Make sure the flute rests on the guide's tip. Repeat the process from the last two steps.

Shut the motor off. Remove the bit. Check width of the center cutting edge on the bit. Adjust the overhang and repeat the grinding process if it is not satisfactory.

Step 15: The Finished Bit

This is how your bit should appear. Notice there are no longer any worn, rounded cutting edges casting glints of light. Everything is sharp and crisp. The length and angle of the cutting edge at the tip of the drill bit are good, too.

Step 16: Small Sizes

A sharpening guide like this one works well for bits 1/8 inch and above. It does not work with smaller bits than 1/8 inch.

Make a special wooden block to serve as a guide for a handstone when sharpening small bits. The angle of the lines in red is 77 degrees. Make the block about 4 inches long.

Step 17: Compound Angles

This is the edge of the block. The angle between the red lines is 59 degrees.

Step 18: A Guide Line

Notice the "V" in the top surface of the block. It runs the length of the block and makes a place for the small bits to be cradled. The angle between the red lines is also 59 degrees. This serves as a guide line to align with the leading edge of each half of the bit. A visual alignment is satisfactory.

Step 19: Placing the Bit Against the Block

Place a bit into the "V" groove on the back face of the block. Place the block into a vise so the end of the bit rests on top of and against the jaws and so that it just barely extends above the angled surface of the block. Turn the bit so the leading edge of the first half follows the guide line. Use a "C" clamp to hold the bit in place. Put some oil on a small handstone, like those used for sharpening fishhooks. Stroke along the angled surface of the block so the bit is being sharpened at the same time. When the stone is no longer cutting on the bit, turn it half of a turn and sharpen the other side. Inspect the bit with a magnifying glass, if necessary.



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    173 Discussions

    Freehand sharpening. Hold the shortest thickness at the point vertical. angle the drill up and down WITHOUT turning it.

    The skill is in the angle of the drill to the vertical. If you go all the way to horizontal you have no clearance. And remember the two main things. 1 keep the shortest part of the web at the tip vertical and 2. Don't turn the drill at all when grinding just change the vertical angle.

    2 questions :

    1. How do I find the correct angle of my drill bits?

    2. Whereas you use a radial saw, I have access to a bench grinder with a small wheel, how do I get my hight alignment?

    Thanks in advance.

    3 replies

    Most probably the angle on your bits is 59 degrees. That is pretty standard unless you have a very specialized bit.

    Although it is not generally recommended practice, you can sharpen bits on the side of the grinding wheel rather than on the circumference of the wheel. Can you temporarily mount your bench grinder on a riser of some kind?

    thank you much. worked out perfectly.


    7 months ago

    I was struggling with the General drill bit sharpening guide and then found your article. I think it will help. Thanks.

    1 reply

    Welcome to Instructsbles. I learned some minor things from my own use, particularly what is in step 11. Check the results you are getting as you go and make minor adjustments. Unfortunately, it is easy to grind away part of the tip against which the flute rests. I began with the directions included with the device and made common sense tweaks. From my side, the purpose of this Instructable was to record those so I did not need to reinvent the wheel after a long period of no use. Since posting this, I finally learned to sharpen drills by hand. It is not nearly as difficult as I thought. A couple of videos at YouTube were very helpful.

    Where can i buy that sharpening tool ? I searched on Amazon but i didn't find it ,can you send me the link? Please?

    1 reply

    Amazon does have it as a General 825 drill sharpener. Search for that. It is about $25 plus shipping, etc.

    This is a great guide and I managed to get a reasonable edge on my first bit! However I am puzzled by the setup with the drill slightly to the left and then sharpen it from the other side... Ie from right towards the left. As the bit kisses the wheel when setup to the left, how can it be turned back to the right to start sharpening when it will pass through the wheel? If you need to move it the why set it to the left in the firdt place? Also after the first pass how is it returned to the right? Or is grinding done in both directions?
    Thanks again

    3 replies

    You can sharpen by swinging the fixture both ways. What I found was it is tricky to know how close to set the fixture (and the front end of the bit) to the wheel. Swinging the axis on the fixture a little to the left and then moving the fixture up to the wheel so the bit touches the wheel grinds just the right amount off of the end of the bit without grinding either too little or too much. It is just a little thing I discovered for getting the right starting point. I think if you try it y will see why I do it that way.

    great tutorial! I have the same Craftsman sharpening tool, inherited from my grandfather and I am excited to salvage some wrecked and worn bits. thanks!

    Thank yu for looking. Feel free to make adjustments so you get the best results.


    2 years ago

    Hey thanks for this awesome guide. I was very perplexed at first on how to operate my drill bit machine, but now I know how. Anyway, I think Drill Doctor sharpener is very good at this job, as I search around for reviews and all recommend this brand, especially this

    1 reply

    I hope it is helpful to you. A friend has a Drill Doctor machine. I used one belonging to my son-in-law. Afterward, I talked with my friend. We agreed a Drill Doctor sometimes does a good job, but there are times when it does not do well at all. I was surprised. I had always thought they would be a sure-fire method. In recent months I have finally learned how to do a fair job of sharpening drills by hand. My results probably are not perfect, but the drills certainly work far better after I am finished with them than they did before.

    I can't believe it...I bought one of these bit holders at a tag sale several years ago. ..brand new in box for $2.00..but no instructions. ..thank you for the great HANDS ON INSTRUCTIONS. .

    1 reply

    Thank you for your note. Congratulations on a really good deal. I bought mine new and instructions were included. But, there wee still some fine points to learn by experience. I wanted to share those so the instructions and the sharpening jig are more useful.

    Be sure to make a wood block with sloped cuts for sharpening small bits 1/8 inch and smaller. Just a few weeks ago I made one of those blocks for a friend who owns a Drill Doctor. He said no matter what he did he could not make his Drill Doctor hold the smaller bits for sharpening. I sharpened a 1/8 inch bit for him in a couple of minutes with the wooden block and a sharpening stone. He drilled some oak and was very pleased to have a sharp bit again.

    It is the short peaked edge of the bit between the two fluted sides of the twist. You can search for bit web at YouTube for a video on now to shorten it.