How to Sharpen Used and Dull Drill Bits (By Hand!!)

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Introduction: How to Sharpen Used and Dull Drill Bits (By Hand!!)

Have you tried to drill something recently and noticed your bits aren't cutting like they used to? Maybe some of your bits are so bad, you can't even get through wood or soft metals anymore without creating a plume of smoke and high shrieking squeaks. Well before you head over to the hardware store to buy yourself a brand new box of drill bits, try this simple technique first and save yourself a lot of time and money!

Follow these steps and you can transform your used, dull, chipped, broken, or otherwise useless drill bit, into a prime hole blasting instrument.

Sharpening bits is a tricky task. When I started my job as a machinist nine years ago, my trainer was skeptical about using any kind of automatic machine or fixture to re-sharpen our drill bits. In fact, you’ll notice that most of those fixturing devices or machines cost a lot of money, and very rarely do they ever give you something close to a factory sharpen (unless of course you fork out enough to buy an industrial sharpener). So what’s going to be demonstrated here is a kind of lost art—sharpening by hand on a belt sander or bench grinder.

Now, I’m not saying that after this tutorial, you’ll be able to achieve a perfectly sharp drill bit, but it will get you through the next job until you get enough practice to really put an edge on your cutting tools. My trainer and I have gotten so good, in fact, that whenever we’re given those cheap HSS China bits (that pretty much everyone has in their garage), we’ll pull them right out of the box and sharpen them before their first use.

So without further adieu, here's what you’ll need:

Materials:

  1. A dull or chipped drill bit
  2. A bench grinder or belt sander

WARNING! Your hands will be very close to the sharpening device, and dangerously at risk with losing some skin. DO NOT wear gloves as they can actually get caught into the sharpening device and pull you in. Be mindful and deliberate about where you position yourself on the sharpening device. And you should probably wear safety glasses too.

Step 1: Know Your Drill Bit

There are many features on a drill bit that can be defined. For speed sake, were only worried about 3 basic features on the bit: the lip, land, and chisel.

The "lip" is what does the actual cutting. The two lips on the twist drill should be symmetric if an equal cutting is to be done while drilling. If one lip is favored while sharpening, it will become bigger than the other and most of the cutting will be performed on one side of the bit. This is bad as it makes non-straight holes.

The "land" or "landing" is what follows the lip and will support the sharp edge while the bit is cutting. The landing must be angled in such a way that it leaves clearance between the part you are trying to drill and the lip. However, too much angle subtracts support from the lip, and will cause the bit to chip more often, especially on the corners.

The "chisel" is the line which is created when the landing from both sides of the twist drill intersect. In truth, this area does no cutting motion. Don't think of it as a true chisel. In fact, while the drill is turning and being forced down into your work-piece, the chisel smears the wood or metal you are drilling into the lips. For this reason, it is especially important to create a very small chisel.

Step 2: Uderstand Why Drills Chip and Dull

In order for you to know how to better sharpen your bit, you should know why you're even doing this.

Chipped bits are caused because the landing force behind them cant support the forces exerted by the drilling operation. So make sure your landing has a curved shape to it. Curved shapes add support to the lip.

Dull bits are caused when either the chisel is having trouble smearing the material to the lip and needs to be re-defined on the face of the bit. Or, the lip is rolling over and needs to be re-sharpened so that it pushes directly into the work-piece.

Step 3: Prepare Your Bit

Run a file across any burrs that bay be on the shank of the drill bit. If anything were to go wrong, and the bit were to slip in your fingers, you wouldn't want these nasty burrs cutting into your skin.

Step 4: Choose Your Sharpening Tool

Either a bench grinder or a belt sander will work for sharpening bits. Just make sure that the guards on either one of these machines is less than 1/8" away from the belt or wheel so that your bit doesn't get caught between the guard!

Step 5: Practice Holding the Bit

Start in a comfortable position with your hand against the machine support and take the drill bit into both hands. Hold the bit at a 60 degree angle to the face of the belt sander. Place the end of the landing so that it is directly against the belt. Use steps 5-7 to move the bit across the belt into the finish position. Notice in these two pictures how little difference there is between the start and finish sharpening positions. Steps 5-7 are simultaneous steps to get you to that finish position but notice how the only hand that moves is the left hand. The right hand stays stationary, with only the fingers guiding the drill bit.

Step 6: Cut the Landing

Cut the landing by raising the left hand while applying pressure to the sharpening device.

Step 7: Shape the Chisel

By moving the left hand towards the right, you will create the chisel angle. Practice a few times until the chisel angle is 45 degrees from the lip.

Step 8: Shape the Landing

By rotating or rolling the bit counter clockwise, you will create a rounded landing that gives more support to the lip.

Step 9: Combine Cutting, Shaping, and Rotating

Combine all three movements while sharpening to make the perfect cut on the drill face.

Repeat this step a couple of times and rotate the drill bit 180 degrees in your hand to sharpen the other lip.

WARNING: this procedure will heat up the drill bit face. Have a cup of cool water by your belt sander or bench grinder to dip the tip of the drill bit into to cool it off. If its too hot to handle, then you are probably weakening the integrity of the steel that your bit is made of. So keep it cool.

Step 10: Repetition

It may take a couple dozen times to get the two lips of the drill bit symmetric. That's normal and requires a lot of patience. But keep on trying! Often rotate which side of the bit you are working on so that you don't favor one side over the other. Always make deliberate cuts, don't try to "feather" a sharp tip by pressing the drill bit lightly into the sander or grinder. This almost always leads to uneven lips or will cause you to roll your lip so that it no longer cuts.

If you've practiced a little with your bit, and have been able to successfully roll and shape your landing and chisel, you are ready to start drilling! Go ahead and try out your bit in a drill press or hand drill. If drilling is still difficult , look at your chisel and landing angles to make sure you've got enough relief. If you see chips only coming off one side of the bit, make sure the two lips are symmetric across the center-line of the drill bit. If you see chips come off of the bit on both sides of the drill bit, your good to go!

Thank you for ready this how-to on sharpening your own bit!

Step 11: A Final Word

If you happened to have purchased these really nice cobalt chromium split drill bits, I've got some bad news for you. That split through the chisel has made drilling a lot nicer for you, but its very unlikely you'll get a good sharpen out of these bits by hand. You really need a machine that can go back and cut the relief on the back side of the landing to reduce your chisel size. Not relieving the chisel just makes too much smearing of the material during drilling and is practically impossible to get through most metals.

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    We have a be nice policy.
    Please be positive and constructive.

    Tips

    This is sort of a tip and question. very small bits are easy to break. they are also quite cheap. I have a very hard time seeing the angles on these bits are have never been successful in sharping them. I just keep extras on hand. What is the smallest size that you would attempt at sharpening?

    Questions

    103 Comments

    If you are not making furniture or drilling steel for some super accurate tolerance, just put the bit to the grinder and put a 50 degree angle. Start at the low part of the wheel and move the bit from low to high. Try to make the angles look like a "good" bit. Put the sucker in your drill, if it drills a hole, you did a good job. For the average Joe in his home workshop, you don't need to get out a micrometer to get a drill bit to work. Most of us Joe's out there have a cheap set of "Stanley" bits. I could throw away dull bits and buy new cheap ones and spend less than 150 bucks in my lifetime on an expensive drill bit sharpener. You all must be tool makers or something. I'm just speaking for us low-skilled crappy projects guys.

    3 replies

    I've only bothered responding to a few comments on this thread, but this one is just so accurate and funny. What your saying is completely true! A lot of people responding are like me and work in a machine shop where you absolutely need to resharpen drills - but most of these people already know how to do it so I have no idea how they got here. Hahaha! You do you man, keep it up!

    TJ

    'We' wanted to see if you were doing it right or full of * LOL

    Oh, I think you should be pretty happy so many people want to add comments to your 'Ible' even people who know ow to sharpen bits like to see if 'thier' method is 'best' or if something else is 'better'

    In the 'olden days'.. we always had a grinding wheel and wire brush mounted on a arbor with (gad) no shield. The motor is on the bottom of the pedastal, with av belt up to drive the arbor. Is is NOT a positive drive machine.. if you get stupid about how you use it you can stall the grinder without stalling the motor, and not get hurt.

    The trick to sharpening bit is as this fella described, except one thing:

    With more room to move, you do NOT twist the drill at all.

    Get the angle right, then -starting at the lip, you move the drill bit straight up, vertically. Follow the natural curve of the grinding wheel. If you look at a clock face.. you would follow the face of the wheel from about the 5 (or 25) mark on the clock, straight up to about the 2 (or 10 min mark). Small drills are more difficult, and too many people make a big deal about 'relieving' drills that really don't need it. That 'back cutting' action is really easy to damage the nice new lip you just created..

    4 replies

    I was taught in mid 70's to use drill flute to get 'correct' rotation. Seen way too many 'sharp' drills done with 'your' method that have rear edge higher than 'cutting' edge. If it works for you, great but there are multiple methods for getting good cutting edge. If you have two equal spirals coming off work, you know it's (probably?) right

    Yes, you get a correct cut IF you have the right feed pressure and right RPM for the bit, type, size, and material being cut. You can ruin a good drill bit by overspeeding and / or not bothering to lubricate. OTOH, I've seen lots of people turn a drill bit into a screw (or pencil point) trying to 'rotate' it when they sharpen it, by hand or 'drill sharpening' machine.

    All you really need to do (lets assert you can get 135 angle , etc correct)... is get the lip even and established, provide support for it so it doesn't chip, and if you will slow down a little... you'll relieve that 'rear edge'. It doesn't have to be a lot... practice and comparing it to new bits will help you get both sides even and to the correct amount. For what it's worth, I was taught this (and a lot of other little machine shop tips) by the First Machinist Mate, USS Floyds Bay, a seaplane tender. On those things, they pride themselves on the ability to make anything, anytime to exact spec, to say the least. Problem is... this was during the Korean War, when you didn't have programmmable CNC machines, and etc. Nearly everything was done by hand to some extent, and came out right EVERY time. I grew up performing to the same USN spec. Errors were not tolerated, you were expected to know what you are doing and why. I'd rather see somebody grind a few bits down to nubbins learning to make them right .. than see them plop them into some machine and "hope" for the best ggg

    Ahh, you were taught' rather than 'shown' how to do it. It would be a major eye opener for you to see the stuff being done 'today' and called 'teaching' I was an instructor and the vast majorityof 'kids' just want to connect up a computer or pay for someone else to do stuff. The youngest student I had was 17 (from Europe), oldest 73 (with worst attitude ever)

    I think he'd do good to add that into the ible.

    I do the opposite when rolling twisting the bit.

    I offer up the cutting lip to the stone and try to get the correct angle.
    You said 60degrees, that's close enough, but 56° to 59° is probably
    better. This gets closer to the preferred 114° to 118° tip.

    Once I have the drill bit at the correct angle to the face
    of the stone. I rotate the bit until the cutting lip to be sharpened is
    horizontal. The drill is now at right angles to the stone face, the lip is horizontal and the bit axis is at ~ 60°.

    Now gently push in holding those three angles accurately, the horizontal and the 60° to start grinding the cutting lip.

    Now
    I start to tilt the bit down at the blunt end and at the same time
    rotate the bit clockwise so that the lip comes up and away from the stone. The area behind the lip now gets ground into that strong curved shape, you were talking about. The
    clockwise rotation is probably about 60degrees (one sixth of a whole
    turn). One does not want to rotate so far that the opposite lip hits the stone grinder.

    Rotate the bit 180° and offer the other cutting lip to the stone face. Set
    your two angles horizontal and 60° and start grinding the lip and then
    the back behind the lip.

    Check looking at the end and see how
    equal the two cutting lips are. If one is slightly short, then that one
    needs a regrind.. Keep checking and regrinding till the two lips match.

    To
    strenthen the cutting lip for very hard materials, I sometimes add an
    extra grind to the front face of the lip. This flattens off the helix
    angle to a new flat face that aligns with the main axis of the bit. This
    leaves the lip with more metal around it. I use a 300 grit diamond file to form this front face.

    You can also use this to narrow the chisel point to about half it's former width.

    When sharpening lathe turning tools, one goes even further and puts a -ve rake onto that front edge for even more strength.

    8 replies

    I absolutely agree with you, andrewty. I am a formally trained toolmaker and this was how I was taught roughly 20years ago. -Jenny

    As a trained toolmaker, maybe you could answer this question: is sharpening a dull drill bit on a bench grinder OK? Doesn't the bit easily overheat and loose hardness, turning it useless?

    material 'softening' or over hardening edge is only a problem when you have carbon steel drills, maybe woodworking stuff? HSS 'should' be able to stand red heat and still cut (depending on Vanadium, nickel, chrome, cobalt, etc. composition) It's more likely that edge will get overheated then 'quenching' may cause micro-cracks in edge. I believe micro-cracks, chipped edges and weird sized holes was only an 'industry' issue in the 70's~80's though?

    To my knowledge, rapid steels are quenched and tempered at temperatures in the range of 400 to 700 degrees Celsius. When the metal gets bright red from grinding, it's well above those temperatures. It may not get as soft as a plain carbon steel when cooling, but it will for sure no longer be very hard.

    Many woodworking drill bits, especially larger ones, are indeed carbon steel, since they're not needed to withstand temperatures too high - wood smokes well below 400 degrees Celsius, and you don't want burn marks in your holes. Carbon steel becomes soft at even lower temperatures.

    If bit changes colour you got it way too hot. The sparks will be red hot but I've only ever seen small (1/8"~3mm) get red at tip when re-shaping broken bits.

    Getting a 1/2" to 1-1/2" drill cutting edge red takes more power than average bench grinder can supply

    Carbon steel, at least, gets into the range of tempering temperatures before it starts to glow. As soon as it turns blue, you're in the danger zone - there's a range of temperatures, above the blue temperature, where it becomes gray again, and in that range you can't really tell if it's acceptably cool or too hot to keep its hardness.

    As apprentice to an Austrian toolmaker 35 years ago, I was taught to use this method. Good to refresh on the geometry though- been doing it so long by eye I'd forgotten the numbers.

    Ja, das ist gut.

    PLEASE...!!!
    All is very nice but please...!!! Do not forget the safety/protection equipment (cotton gloves and polycarbonate glasses).

    1 reply

    Gloves are extremely dangerous to ware while using rotating tools.