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

Picture of 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

Picture of 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

Picture of 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

Picture of 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

Picture of 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

Picture of 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

Picture of 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

Picture of 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

Picture of 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.

Comments

andrewty (author)2017-02-02

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.

JennyT51 (author)andrewty2017-05-04

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

jtobako (author)2017-04-07

Different material, different angle. If you are going to the trouble of sharpening them, then make a specialty tool

http://bbs.homeshopmachinist.net/threads/51865-quot-4-facet-quot-vs-quot-split-point-quot-drill-grind-definition

burchettme (author)2017-01-24

I would use my bench grinder but Yonaton24 mentions a Grit #. Wouldn't that only apply to a Belt Sander? There are two wheels on my Bench Grinder, one coarse and one fine. Which would be better? R.L. Burchett

TjB29 (author)burchettme2017-03-06

you can use both. Use the course to remove the damaged material quickly without overheating. then switch to the fine to hone it in - so to say.

zacker (author)burchettme2017-01-25

id say use the fine... youre only trying to sharpen the bit. the coarse wheel would be more for re shaping... or if you were starting with a bit with no edge on it. then again i could be totally wrong but i dont think i am if its anything like sharpening wood turning tools...lol

Kuberkoos (author)2017-01-26

I was taught (55 years ago), that the angle should be 57º not 60º ???

TjB29 (author)Kuberkoos2017-03-06

I learned that its 118. When grinding by hand however, 59 is the same as 60 so me. Plus this is set up for people who have never done hand grinding before, so I don't stress the technicalities.

GregS188 (author)Kuberkoos2017-01-26

Yep .... I'm from that same era as well ... and as with crazypj quote as above, in those days the magic number quoted used to always be 118 degrees of relief ...Even now, after all these years I can still pretty much tell by 'eye' when close enough really is good enough which is always confirmed when you start to do 'the job' ! Least ways good enough to do the job correctly. The other thing I have learnt over time is whether people quote 114, 118 or even 120 degrees of relief there really is bugger all difference unless using a very slow rotational speed ... This is definitely an acquired skill that takes lots of practice to get just right !

KevinV116 (author)2017-01-28

As with a lot of these posts, the 'oldies', the category I fit in, were taught by equally professional 'old farts' and it comes down to knowledge and practice, practice, practice. There is a gazillion of sharpening tools on the market and maybe one or two actually work but nothing beats doing it by hand and doing it right. Practice.....

Yonatan24 (author)2017-01-22

What grit# do you use for sharpening on your bench grinder. Do you change it for different sized drill bits?

Thanks.

GregS188 (author)Yonatan242017-01-26

For my 2 cents worth ....Medium to medium fine works well for me so I generally use around 220/150 grit either on a 'good and square' grinding wheel or disc sander. Generally though, the small the bit the higher the grit (e.g. 1/8" or 3mm you may use 220 grit or even higher and say 1/2" or 12mm you could use the use the 150 grit, as you probably need to be just a little more aggressive. (Others I am sure will have their own preferences ....) Do not apply too much pressure to the sharpening stone area via the drill bit you are trying to sharpen. Hold the job firmly but not too tightly, as you still need to be able to release the drill bit immediately should it ever bite into that sharpening surface too much so to speak so as to avoid a personal injury. And, just keep practicing ... Lets face it, these drill bits are already no good, so what difference ...

Yonatan24 (author)GregS1882017-01-28

Pretty much what I thought. Sharpening a 2mm drill bit was nearly impossible on my antique drill powered bench grinder with a 60 grit wheel. It's the only one that I have though.

ArthurS22 (author)2017-01-26

I've been sharpening drill bits by hand for over 20 years now, ever since my auto instructors taught me to blah blah blah, math, yadda yadda, science science, WRONG!!! WRONGWRONGWRONGWRONGYWRONG WROOOOOOOONG!!!!

I accidentally stumbled across the single fastest, easiest, and most importantly, most effective way to sharpen bits without expensive machinery; just a simple bench grinder and some safety glasses are what's needed. That, and a brand new bit that is untouched and still has that factory fresh finish on the business end.

Mate the lip up to the flat edge of the grinder's wheel (while grinder is off) while looking straight down between the tip of the bit and the edge of the wheel that will be doing the grinding. Make sure to note the angle of attack in all three dimensions relative to the grinder, the wheel, and especially the deck you support bit against while grinding.

Set the new bit aside, and mount the one to be sharpened into your drill, and make sure it's set to reverse so it rotates counter clockwise from your perspective. Turn the grinder on, get the drill up to speed, and very, VERY gently press the tip of the rotating bit into the moving wheel while replicating the same angle of attack as you noted earlier with the brand new bit.

The new cutting edge of the bit will auto center by sheer virtue of it's rotation and relative position to the grinder. Practice makes perfect, and you will most like go through several bits while working your way along the learning curve so start out with something uber cheap you don't mind relegating to the scrap pile. You may also want to wear a full face shield as well as it can get ugly if you get it wrong.

But if (when) you get it right, you will be able to sharpen them tens times faster with far more satisfying results; Gottah Blast!

DIY Hacks and How Tos (author)2017-01-22

I probably need to do this to all of my drill bits.

Just a thought for those thinking of running out and sharpening their whole index. Most bits have nitride coatings a few thousandths thick. Once you touch the tip to a sharpener it will dull twice as fast. Therefor never sharpen a drill the first time until you must. After that you will have to sharpen it frequently.

AlanM66 (author)2017-01-26

I have been sharpening drill bits by hand since I was taught how to do it as an apprentice fitter and turner over 50 years ago.

Unlike in the video I start at the cutting edge and raise and twist the drill to grind the back clearance.

If you have never done it before it does take quite a bit of practice to get it right.

The important thing is to get the angle the same both sides, the length of the cutting edges the same and the height of the outer corners of the cutting edge the same with about 4 deg of back clearance - if drilling metal. It can be a bit more if drilling wood.

Also as stated - don't let the drill get so hot that the metal starts to discolour. Carbon steel drills are softened quickly if they overheat. High speed drills are a little better in that regard but still don't let them overheat.

For drilling metal such as brass and bronze the cutting edge needs to be flattened to a width of about .25mm to .5mm (depending on drill diameter) parallel to the axis of the drill so that the drill doesn't grab and pull itself into the metal. This can be done on the grinding wheel if you are very careful - or by hand using a diamond hone.

For drilling metals like steel I like to use a cooling/cutting compound, Tallow (animal fat) works well and is cheap. Or you can purchase "Soluable oil" which you mix with water.Drills will stay sharp longer with a lubricant.

For drilling stainless steel I use a product called "Trefolex" available from engineering supplies.

For drilling aluminium and lead use kerosene as a lubricant. The same goes if tapping metals.

zposner (author)2017-01-26

My machine shop teacher made us get really good at it.

crazypj (author)2017-01-26

A sharp 60 degree drill is way better than a blunt 118 degree drill bit (that would be a 59 degree angle) I was taught to use a pair of hex nuts as a check as it will automatically give a 120 angle

mikedesmalta (author)2017-01-26

maltatool

Need an exact hole but don't want to buy a reamer? here is a simple toolroom tip.

Take a new drill, the size of the finished hole, and with a whet stone lightly make a tiny radius on the two cutting lips, making sure that the cutting edge is still positive.

Then just use as a normal reamer. Drill a hole slightly smaller and finish with the modified drill at a slow speed and if possible a thickish lubricant.

This method never failed me in all of my toolroom days.

Don't forget to regrind the drill before using it for normal drilling

Explorer1 (author)2017-01-26

The color on the drill bit tells me that it has been in its earlier life over heated to a point where it lost its temper, so sharpening that now soft end of the bit should stop right here, next grind away all the colored portion of the bit on the coarse grinding wheel without overheating that end of the bit, you don't want to see no colors, all ways dipping it into cooling water, now you can start to reshape your drill to the proper angles for the material you want to drill holes in, now use the fine grinding wheel, pay attention to simetry, or you will drill holes larger then the nominal size of the drill.

I have been sharpening drills for over 76 Years, and it all ways gave me great pleasure to instruct young aprintes in the proper way to sharpen your tools.

lae52 (author)2017-01-26

I learned to sharpen bits on the side of a bench grinder wheel. It's much flatter and easier to control the grind. I also start on the cutting edge first and lower the back of the drill to relieve the metal behind the cutting edge. Using a coarse wheel will create less heat than a finer wheel will. The metal will be removed faster. Also always sharpen the bit without gloves so you can feel the heat if the bit is starting to heat up.

zacker (author)2017-01-25

i bought a drill DR and all i can say is, it sux. no matter how hard i try i cant get a good sharpening from it. lol

tytower (author)2017-01-23

Well I have never rounded off the backs like that . Will try it, but it looks wrong .Definitely wrong is grinding to such an extent the tip gets hot . Slow down ,less pressure and shorter times . if it gets hot you soften the steel .Same goes for chisels and the like. Cooling it in water won't help the damage is done.

cmonster6 (author)2017-01-22

on the split point bits I grind the relief first then sharpen as shown easy peasy just takes lots of practice

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