Drill bit sharpener

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Dave Taylor
Does anyone sharpen their drill bits? Working on a project today I was reminded how messed up my large bits are.
Hand sharpened on a grinder with mixed success.
Pal said his shop swears by this Drill Doctor Replacing all my large bits is going to be $150+ so I’m thinking about this.
Metal cutting bits, 1/4”-3/4”
Do bits have a hardened edge which would be lost with sharpening?

https://www.drilldoctor.com/shop/product-category/sharpeners/
 
Does anyone sharpen their drill bits? Working on a project today I was reminded how messed up my large bits are.
Hand sharpened on a grinder with mixed success.
Pal said his shop swears by this Drill Doctor Replacing all my large bits is going to be $150+ so I’m thinking about this.
Metal cutting bits, 1/4”-3/4”
Do bits have a hardened edge which would be lost with sharpening?

https://www.drilldoctor.com/shop/product-category/sharpeners/
Drill bits are usually made of "high speed steel" which is very hard. There are various coatings used, but they don't make enough difference to worry about.

I have a drill doctor and generally like it. It's not perfect... about 75% of the time it produces a satisfactory cutting edge, but they usually wander more than a factory ground bit. If you have good eyes and patience, you could probably learn to do a better job by hand, but I have neither of those

My DD is around 8 years old. I haven't looked at their offerings since then, but at the time it was the most expensive one they sold. Previously I had one of their cheaper models, but it could only do up to 3/8. The one I have now can do 1/2, or maybe even 5/8, I'd have to look. It still feels like a cheap plastic toy, but it does the job. Nothing I hate worse than a dull bit, except maybe when an index is missing one or two bits.
 
Drill bits are a compound angle on a cylinder on 2 sides of that that cylinder that need to match. I’m meh on the drill doctor, but better than by hand w/no experience. If you have a local sharpening business, they should have a high end drill bit sharpener that will take the bit back to new sharpness. Yes, w/practice you can sharpen by hand, they’re just rarely 100%.
 
Does anyone sharpen their drill bits?
In my experience, it depends on the drill bit quality, precision needed, or the job at hand whether its worth to sharpen. I consider any bit smaller than 5/16" as consumable and replace as needed. Quality wise I buy at whatever level dictated by the job at hand. Larger than 5/16" I have a high quality index set that can be sharpened a number of times, if needed. But have only sharpened the 3/8" bit twice. FWIW: the life of any drill bit depends on how you use it and selecting the right bit material for the job.
Do bits have a hardened edge which would be lost with sharpening?
Usually the quality of the drill bit will determine that. While hardening varies, on most cheap bits that hardening can be worn through during its use and definitely via sharpening.
 
Does anyone sharpen their drill bits? Working on a project today I was reminded how messed up my large bits are.
Hand sharpened on a grinder with mixed success.
Pal said his shop swears by this Drill Doctor Replacing all my large bits is going to be $150+ so I’m thinking about this.
Metal cutting bits, 1/4”-3/4”
Do bits have a hardened edge which would be lost with sharpening?

https://www.drilldoctor.com/shop/product-category/sharpeners/

I have one of these, and they do work. But I have found that the sharpened drill bits don't last nearly as long as the new ones, probably because of the lack of coatings. Eventully, I ditched all my drill bits and bought new ones.
 
Buying drill bits can be hazardous. There are so many levels of quality out there, and good stuff is expensive.

There are at least five bit materials: Carbon steel, the cheapest stuff. High-speed steel, which has more carbon and other alloying metals in it. Cobalt steel, which is HSS with cobalt added for hot hardness. There are the TiN-coated bits, the yellow ones, plated with titanium carbonitride. That's a hard coating that makes the cutting easier and acts as a friction-reducer. Sharpening that bit removes the TiN from the cutting edge. And then there are the solid carbide bits, much more money, but can cut under high heat. They also chip easily, and if you use coolant you have to flood them or leave them dry. Anything in between causes thermal shocks that crack and fail the bit.

I sharpen my bits by hand, even some tiny ones, but if you don't get both flutes right at the same angle, and the chisel edge right exactly in the center, it will drill an oversize hole. Too much rake leaves the cutting edge too thin and it overheats. Too little and the heel drags.

Never used a Drill Doctor. Had a chance to buy one real cheap many years ago, and should have. I have sharpened, by hand, bits from #40 (not much success most of the time) up to 1-1/2" or so. Big ones are easy.

Lots of stuff on the internet as to how to do it. Stuff like this:

upload_2022-5-28_11-48-12.jpeg

Thinning the web, if done right, will make a bit drill like mad and will generate a lot less heat. he idea is to shorten the length of the chisel edge.

upload_2022-5-28_11-50-2.jpeg

Or:

upload_2022-5-28_11-51-20.jpeg

I have also re-heat-treated bits that have been overtemped. Sharpen them first, then heat the end to a dull red and quench it in water or oil. Clean off all the oxide, then heat very gently until a straw-colored oxide appears, and let it cool. Then give it a final sharpening. Big expensive bits are worth this. Not the average smaller cheap hardware-store stuff.

New bits that chip easily haven't been tempered enough. They're too hard. Do the gentle heating to get the yellow oxide, and they'll work better.
 
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My dad could sharpen drill bits fast and accurately by hand well into his 80's. That is a skill I definitely do not have. I have used the drill doctor with varying degrees of success.
 
There is a Youtube channel called "project farm" where he reviews tools along these lines, and did a report on drill bit sharpeners. I really don't remember the outcome. It's a good channel, though.
 
DD works great for me. I learned to sharpen drills on a grinder years ago but laziness got me and I bought one. It takes some practice to get the DD to work well, but once you get it, it's fast and easy.
 
I hand sharpen my bits all the time. It's not that difficult except for the tiny sizes. BTW if you want a precision sized hole taper the drill so it only cuts with the side after drilling a pilot hole slightly smaller. This way it acts like a hone.
 
Yes, you are right I meant a reamer. The hole will be much more precise that a drilled hole which tends be slightly oversize due drill point being slightly of dead center.
Most drills, if the point is right on center, will drill slightly undersize. Just take a micrometer to a bunch of them and see what you get.
 
The only way this seems possible is that the drill friction expands the metal slightly while drilling and when the metal cools it shrinks a bit.

I have never had a need for a precision hole but the reamer from drill idea came from Alec Clarkson who invented the Britain Autopilot (sp?) with the idea of using a single tilted rate gyro to stabilise both roll and pitch. He also invented the Super Venturi to both power the gyro and the rolling diaphragm actuators connected to the ailerons for airplanes without vacuum pumps. He held many patents and was an expert machinist.
 
I spent about 90 minutes today becoming familiar with my new DrillDoctor.
I bought the best one listed, 750X - $150.
It's good. I like it. There is some study and learning involved. You don't just flip the switch and stick your bit in it.

There is no way a person could, by hand, match the precision grinding - which must be equal on both sides of the tip of a bit - that this device can do. Yes, you can hand grind pretty good; I've done it - but for the average dude who does not live in a shop all day, this tool makes it easy to do that and probably much faster. (And there is the exceptional craftsman out there who can almost match this, but few have the time or skills for that. This dumbs it down for us.)

As my first victim, I took a bit that had the tip pretty much destroyed. Before sharpening, I tried drilling soft 1/8" steel plate with it and made a bunch of heat and noise, it pushed metal up around the edge of the hole, so it was obviously toast. Essentially, I was starting from a blank bit & going to make a new cutting tip.
I needed to become familiar with the tool terminology in their booklet, and figure out what they want you to do. Several times I had to backtrack to revisit what was said and what I was doing wrong but I eventually figured it out.
There is some fiddling required to get things set up just right. Unless you have bright light and great near vision, it can be hard to ascertain the chisel point angle, for example. I had to make trial and error cuts to produce an angle of around "1:30" (per their diagram) which is where my bits seemed to cut best.
Also there is no guidance on how hard to press the bit onto the spinning drum. I was skeert of bending the 3/16" shaft that it was mounted upon. Or overloading the motor. So, I went slow. This bit was not a touch-up so I had to remount it several times in order to grind so much off. Really should have bought the course drum to do this. Anyway the result was that this bit eventually drilled through that 1/8" steel plate like it was a new bit.
Will it last? I have not done trials. I am not too concerned though because I know I can put a new edge on it in a matter of moments now! Maybe I will get fancy and learn how to temper them in hopes of retaining the sharpness longer.
I proceeded to sharpen and test a number of bits; 5/16" and less - with not too much trouble (had to alter the chisel point angle again in order to make the smaller bits cut well.)
I also did all my masonry bits (completely different technique, but easier). Can't wait to try them; they look great.
The only thing I have not been able to do is the split-point grinding. It seems to be consistently under-grinding...but the bits work fine without that.
 
I spent about 90 minutes today becoming familiar with my new DrillDoctor.
I bought the best one listed, 750X - $150.
It's good. I like it. There is some study and learning involved. You don't just flip the switch and stick your bit in it.

There is no way a person could, by hand, match the precision grinding - which must be equal on both sides of the tip of a bit - that this device can do. Yes, you can hand grind pretty good; I've done it - but for the average dude who does not live in a shop all day, this tool makes it easy to do that and probably much faster. (And there is the exceptional craftsman out there who can almost match this, but few have the time or skills for that. This dumbs it down for us.)

As my first victim, I took a bit that had the tip pretty much destroyed. Before sharpening, I tried drilling soft 1/8" steel plate with it and made a bunch of heat and noise, it pushed metal up around the edge of the hole, so it was obviously toast. Essentially, I was starting from a blank bit & going to make a new cutting tip.
I needed to become familiar with the tool terminology in their booklet, and figure out what they want you to do. Several times I had to backtrack to revisit what was said and what I was doing wrong but I eventually figured it out.
There is some fiddling required to get things set up just right. Unless you have bright light and great near vision, it can be hard to ascertain the chisel point angle, for example. I had to make trial and error cuts to produce an angle of around "1:30" (per their diagram) which is where my bits seemed to cut best.
Also there is no guidance on how hard to press the bit onto the spinning drum. I was skeert of bending the 3/16" shaft that it was mounted upon. Or overloading the motor. So, I went slow. This bit was not a touch-up so I had to remount it several times in order to grind so much off. Really should have bought the course drum to do this. Anyway the result was that this bit eventually drilled through that 1/8" steel plate like it was a new bit.
Will it last? I have not done trials. I am not too concerned though because I know I can put a new edge on it in a matter of moments now! Maybe I will get fancy and learn how to temper them in hopes of retaining the sharpness longer.
I proceeded to sharpen and test a number of bits; 5/16" and less - with not too much trouble (had to alter the chisel point angle again in order to make the smaller bits cut well.)
I also did all my masonry bits (completely different technique, but easier). Can't wait to try them; they look great.
The only thing I have not been able to do is the split-point grinding. It seems to be consistently under-grinding...but the bits work fine without that.
Remember, don't stick your fingie where you won't stick your dinkie.
 
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