Sharpen Your Drill Bits

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.

Comments

[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.