Sharpen Your Drill Bits

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.

Comments

[shazni]

how do i shapen a spiral scroll bit which is supposed to cut sideways too?
it's 1/8"...i use it for my rotary tool and i only can get new once from abroad

[Phil B]

I would get a fine, hard stone like a hard Arkansas stone and dress the bits by hand. It is not perfect, but it might help you.

[shazni]

how do i shapen a spiral scroll bit which is supposed to cut sideways too?
it's 1/8"...i use it for my rotary tool and i only can get new once from abroad

[flywelder]

Phil or any body,
I have inherited three drill bits made by the Union Twist Drill Co. a No. 8,
No. 6; and No. 9 They need sharpened, and I have yet to find any one who can sharpen these or tell me how to . the interesting thing about these bits is they each have three cutting edges. yes three. there is a pencil point surrounded by three flutes. Help.
3-01-2012

[Phil B]

Wow! I have heard of numbered sizes. When you want to drill for tapping threads the recommended bit is usually a numbered size. But, I have never heard of a bit with three flutes. I would ask questions at a local machine shop to see if they can help.

[ronbuffington]

I thought these were called drills, not bits. Drills may be used with drill motors, but bits are used with a brace, i.e. a brace and bit.

[quahogwi]

I'm a little late getting into this, but the compulsion do do so is overwhelming. The distinction is simple. A drill is the machine or tool or action used to make a hole in some material or other, usually a hard material. A drill bit is the cutting piece or edge of the tool that makes the hole. There may be minor nuances as to where the ":drill" ends and the "bit" begins, but at it's core the drill is the tool, whether motorized or not, while the bit is that part that bites into and removes the material and actually makes the hole. So, you sharpen the bit and not the drill itself.

[quahogwi]

I failed to mention that I thought this -able very good and worthy of downloading the pdfl.

[Phil B]

You are probably correct. What I wrote reflects what I have heard all of my life. I expect others have heard it as I did, too, whether right or wrong.

[ronbuffington]

Phil,
I should not complain, father being a carpenter, drilled, into me what a drill was.
you and i are same age , different backgrounds. Good Work.

Ron

[Phil B]

Ron,

That reminds me of something my mother drilled into us. She was a registered nurse. My brothers and I were the only kids in our one-room elementary school who could tie a tourniquet. Further, if at age 5 or so, multiple people needed one, we were to write TQ on their foreheads in lipstick so we would know to come back and release the tourniquet periodically so that the tissue beyond the tie point would not die. I do not know where we were to find tourniquets or lipstick, and I do not know that anyone would ask a 5 year old to handle such things, but we were trained and ready.

[GadgetBuilder1]

Drills with grind lines parallel to the lip tend to fail prematurely due to flex at one of these grind lines. See the picture here for an example of this failure:
http://www.gadgetbuilder.com/DrillSharp.html#Inexpensive

Raising the contact point well above the grinder shaft avoids this problem.

[montanasoftware]

Excellent writeup ... you are a wealth of knowledge. I also enjoyed your DIY radiator pressure tester, and have already assembled a brass T-Fitting for heater-hose access.

Thanks!

[Phil B]

Thank you. I am almost older than dirt, so I have had time to learn a couple of things. Thank you for starting on the radiator pressure tester. I would be interested in seeing a photo of your T-adapter sometime.

[msw100]

Is all this not automatic with a bit sharpener,I do mine by hand on a grinding wheel and they are as sharp as any done on a machine

[marksteamnz]

Hi Great instructable
Just wondered why in step 12 the tip appears to be dragged across the grinder face before starting the wheel and then swung back. Would it be better to swing to the left, start the wheel and then swing to the right?

[Phil B]

The answer to your question is that the post on which the jig swings is not exactly vertical, contrary to expectations, but it has a forward caster that causes the bit not to make contact with the wheel where in its swing arc you would expect it to make contact. You can get a hint of that forward caster by looking at the profile photo of the jig in step 2. Compare the plane of the jig's base on the bottom with the slight forward angle where the base connects to the upper part of the jig. If you are familiar with the three angles involved in aligning the front wheels on an automobile (caster, camber, and toe-in), this will make more sense to you. Step 13 gives a better impression of where the tip of the bit is when it makes contact with the wheel. Also, I like to swing the tip far enough to the right before starting the motor so that there is plenty of clearance and no possibility the bit and the wheel are in contact with each other when the motor starts. Thank you for your interest and for looking.

[inad]

This is a great series. Wonder if you could do a parallel instructable showing free hand held technique for sharpening drill bits. some oblique photos would be a great help.

[Phil B]

Thank you. I am glad you like it. I hope it helps you when you sharpen drill bits. If I had mastered sharpening bits by hand, I would gladly do an Instructable on the process. I did find a couple of pages that briefly describe how to do it, and alluded to the basics early in this Instructable. Perhaps one of the previous commentators who has learned how to do it would consider producing such an Instructable. I do not believe myself to be qualified to do it.

[jack8559]

I don't have access to a camera or recorder, but there is a book that may help if you can find a machinist or engineer that will let you look through their copy. It's called MACHINERY'S HANDBOOK. The book is expensive, at least by my standards - around a hunderd bucks US money. There is a wealth of information in there on a lot of things mechanical. You may be able to find an old used one on ebay or someplace for 30 or 40 dollars - well worth the money!

[jack8559]

As a machinist, I have sharpened thousands of bits - all by hand. If they are really small (under 1/8") I usually just get a new one since we never had a sharpener that I had any degree of faith in. A note for everyone that attempts to hand sharpen a bit... always look to be sure that from the cutting edge that there is relief behind it. I have seen so many people that claim to be able to sharpen a bit and they come back with the trailing edge of the bit higher than the cutting edge and they wonder why it won't cut.
If a bit is going to be drilling hard material, you will want the end to be more flat so it won't dig in and dull fast, and you will ALWAYS want to center punch your mark to prevent a drill from 'walking'. The 59° angle used on most sharpeners is a standard angle for mild steel - for softer materials make the point more like a pencil but be careful of how much more pointed you make it, it could try to screw itself into the wood, plastic or whatever you're drilling. I guess my point is to go in small steps until you know what works for you!
Try starting with a large bit if you aren't familiar with the procedure and remember that if the steel gets hot enough to turn black at the cutting edge, you have just removed the carbon from the edge and it will dull VERY soon. You must grind the metal slowly and dip in water or some other coolant frequently so as to prevent that. Get a new bit to look at after you have tried your hand on a big one and see what the difference is, there should be very little. When thinning the web, remember that the thinner the web, yes, the easier it will penetrate the work, but also the easier it can grab and split the drill down the center making the drill bit trash immediately. If the sides (lands) are worn on the drill bit, it WILL grab and break off many times when you need it most - inspect drills before using them to keep from ruining your project... After grinding, hold the bit up with a bright background behind it and with the cutting edges going left and right from your body - you need to make sure that both the tips are the same height and that the point is in the center before you attempt to thin the web if it is needed. If there is a pilot hole with a greater diameter than the thickness of the web, no thinning will be required.
Whne grinding by hand, always hold the cutting lip level against the wheel at the center height of the wheel and rotate the drill upwards to make the relief. Grind slowly and don't try it with a wheel that is out of round, you will get hurt badly. Dress the wheel to be true before starting any grinding process. Always use safety glasses or goggles when grinding and if there are any questions, stop what you are doing and research it- SAFETY FIRST!!

[nedward]

do you use a slow grinder 1800 revs i am a qualified electrician from sout africa rsa southafrica i use a norton white stone on 2400 rev grinder small bench grinder i find the grey stones hard on the drill only use white wheel i come from a farm where we sometimes use an angle grinder for a quik sharp your article is exellent with safety and all is the relief part the thickside from the cutting edge downwards 118 degrees on the slope on both sides must be even it is an art to grind freehand but i cant sit in the field with jigs the work must go on blunt drills scream i also use lubricant when drilling electrical cuttinpaste nice talking to you nedward

[jack8559]

At work, I used a regular bench grinder, which means that you need to lightly touch the bit to the spinning stone, rotate the bit, cool it in coolant preferably, but just plain water will do fine, repeat until you have finally got it really close enough to suit you, then gently and lightly grind the finishing touches all the way from the cutting lip to the trailing side to get the relief right and cool it again. It takes a while to get it right. A great thing to do is get a new bit and never sharpen it, just use it to look at while grinding the old bit so that you know what you're looking for in the hand sharpened bit - use it as a comparison for the point.
The 59 degerees is the angle on one side of the bit to the centerline of the bit, so the 118 degrees that you mention is the same as what I'm doing. The finer the grit you use means that you will have to dip it in water or coolant more frequent but it will give you a better grind as well. I have used a 60 grit wheel and gotten good results, it's just a matter of taking your time and knowing what to do. Practice makes perfect, and then when you think that you've got it, then practice a lot more..... you'll see that there are ways to do the job and make it a lot faster and still not burn the bit! If you never have made the metal black or blue at some point during sharpening the first hundred bits, you have not really tried like you should. Know when it will turn blue and stop short of that. Small bits will turn blue a lot faster than larger ones due to the mass that will have to be heated from friction to cause it to turn color and burn the carbon out...

[Phil B]

The motor on my grinder runs at 3000 rpm. I use what I have available. I do not have a white stone. Thank you for looking and for commenting.

[MTJimL]

I thought I was good using a drill guide and sharpening by hand. Being able to accurately eyeball the slope, clearance and centricity without a guide seems truly remarkable.

[jack8559]

MTJimL:
This is not something that you can pick up in a few days, maybe not in a year. I have sharpened bits for over 25 years (daily) to do as well as I do. The first thing that someone needs to do when attempting to sharpen by hand is to really study drill point geometry closely. Understand all the parts of the drill and what their specific function is and why it is needed to be the way that it is. Once you understand all this, you must try a few thousand bits before you get it close enough to perform well for your application consistently.

One point to remember is that the angle of the point must be reasonably close to what is recommended for the application that you are going to use it for. the more pointed it is, the more it will tend to pull itself into the material being drilled, so that material must be soft enough not to split the drill down the web. The harder materials will be better served drilling with a much less point on the drill - almost a square end. The relief behind the cuting edge has a bearing also - hard materials need to have a relatively low relief (.001 to .003") and softer materials like wood should have a more pronounced relief(.010 to .020"). If a material is not drilling fast enough, it is probably due to the web being too thick and must be thinned OR the relief is way too shallow. Be careful to closely inspect the lands for drilling materials like bronze, this material tends to wear out the lands and the drill will grab and split the drill down the web and break off in the hole - not a pleasant task to remove. It takes some homework to fully understand drill bits even though they are as common as they are.

[tomas.savage]

good advice. i'm a jeweler and i sharpen my tiny drill (1.5mm or smaller) bits by hand all the time. i use an ultra-thin cutting disc and hold the drill in a pin vice. it was a matter of trail and error until i learned how to hold the bits and tools at the proper cutting angles. the cutting disc can even sharpen/deburr worn lands by running it through while rotating the pin vice.

[note: with this method, it is even possible to restore some life to other rotary tool bits, though i would use them for roughing work]

[Twicewidowed]

As an old time machinist (now 84 yo) I agree. Hand sharpening drills is an art learned over years of experience. Production drills should always be machine-sharpened however. Two equal sized spirals of blue hot steel emerging from a bath of cutting fluid is the mark of a well sharpened drill but having the ability to touch up a slightly dulled drill by hand is a real time saver and an indication of craftsmanship.

[baudeagle]

Great response, your comments above are in essence the same as what a mold maker taught me a long time ago.

One tip on drilling large hole, if using a pilot drill, use a small diameter drill compared to the diameter of the finished hole. The the pilot drill should not be smaller than the thickness of the larger drill's web.

Thanks for your comments.

[Phil B]

Thank you for a very helpful comment. Regular practice has to be a key component in the proper sharpening of bits by hand. Even if I was careful to keep the heel lower than the cutting edge, I had trouble getting the slope angle equal on both sides and with keeping the web centered between the opposing sides of the bit. I stand in awe of anyone who can sharpen bits by hand and do it right.

[grigsby]

Almost 70 YO. Journeyman Mold maker. Have sharpened a lot of cutters. Even spiral taps. Oh, I ground taper by machine and then cleared each one by hand. Then checked each one by tapping a hole in Aluminum. I have been told the best/worst joke is to substituts a left hand drill in machine when a new guy takes a break. I haven't tried it but have thots of some bad communications. NO I haven't done that. The best idea I have heard is to sharpen end of a drill blank left handed so broken bolt will screw out when trying to remove a broken bolt. I love it. Drill blank will look like a broken center drill, only with left hand cut. Yes, 1/16 drill can be sharpend by hand even tho I can't see end of drill.

[MTJimL]

When I was in the business I had to sharpen bits by hand; the owner was too cheap to buy a drill sharpening jig. I used a commercial, sheet metal angle guide/scale and a very light touch to finish the grind. I could usually grind them to cut within .005" of their nominal size. The hilarious thing is the owner could have bought a quality sharpening jig many times over for what he paid me to do it by hand.

What amazed me was how many production "machinists" had no concept of a properly ground tool. I don't know how many times I tried explaining cutting tool rake and clearance angles.

[Narlo11]

Hey grigsby I also make molds (fiberglass and concrete). Where did you get journeyman certificates? As far as I know there is no such thing. Im in Canada and have looked into it. All I know of is CCT. So I can say I am a journeyman but have no papers.

[grigsby]

I am in IN. I build molds for injection plastic parts. My journeyman papers were issued by US labor board. I also have certs for my shop to train moldmakers/ machinist. I own mold building and molding shop.

[dwhite0]

Sorry, but I do not see this device on Amazon. Would you be so kind as to give us more complee details on the sharpener: such as Manufacturer, model number and any othe identifying notations. Your phot reveals the word craftsman?

[Phil B]

Amazon has it under two listings. One is more than twice the price for the same item!

$7.99

$16.95

There is one company making and labeling them for whomever wants to sell them.  Just click on the hot linked price you wish to pay. 

[anode505]

I disagree with the ability to sharpen by hand. Yes it will be sharp, but right? Doubtful. Unless both sides are even, it will not cut the correct sized hole.
People that claim they can do it are just lucky once in a while. I say test a hole with a pin gauge; you'll find its cutting large.

[stoobers]

The hole down the center of a gun barrel is cut with a drill bit with a SINGLE flute - not even a double flute! And the hole is straight and true for several FEET.

You don't need two sides to the bit to make the bit cut. If you have a bit with two flutes, the bit will cut twice as fast as a singe flute bit.

Upon close examination, a two-flute bit will cut a triangular shaped hole! (trochoidial shaped). If you want the hole round, drill it 1/64" under and ream it out. If you need to thread the hole, you can skip the ream.

[andrewuk]

Bought this tool on Amazon UK for those of us that are on the otherside of the pond.

Search for "Draper Drill Grinding Attachment" brilliant only £17.02

[weldor]

How about info on sharpening for hardened materials? For wood I was taught to sharpen the bit to a radical 90 deg so that the bit does not cause the wood to splinter when the bit exits the work piece. This actually works great!