Sharpening twist drill bits freehand

[Tom Bussey]

If you buy a jobber drill out of a hardware store the drill point angle is a 118 degree included angle not 120. It is a 59 degree angle and not a 60. The other normal angle that it can come in is 135 included angle. I am sure one can get them in about any angle for special applications. Having said all that any angle close to that will work. The main points a to look out for are is that they are as close to the same angle as possible and the flute lengths are as equal as possible. I sharpen free hand but it does include a drill gauge. I like to stay at 59 degrees as closely as possible. It is easy to change angles when grinding and it is also easy to get one flute longer than the other. Hence the gauge which also has lines on it and I veneer the lines. Just so you know if drilling copper ,copper likes a single cutting edge not 2 so the drill point is drilled odd center with one flute longer that the other. Copper conducts heat very well and it can heat up and actually cease the drill bit.

Having said that steel on the other hand likes flutes of equal length. Also a drill of one flute being longer than the other will also drill a larger hole than the drill size That is where probable hole size comes into play

Now to sharpening. First of all you have to train your mussels so do not expect preface points right out of the gate. Place the drill onto the wheel ( eyeballing the angle of the point parallel to the grinding wheels face). I use 2 hands one top close to the wheel for support ad the other closer to the body . one closest to the body is dropped down and there is a twisting motion at the same time. Do not ride the drill point up the wheel but the grinding should be dun when the point is dropped. You can move it up and down the wheel but do not let it ride up always down. You will know when you are at the cutting edge because you should be see sparks come over the the cutting edge than drop the body hand and slight twist the drill at the same tine.

I bench grinder works best for this operation and the stones that come on the grinder will work but for me a 180 CBN wheel is ideal. Fine enough to get a good sharp edge but course enough to remove metal without heating the wheel. I find it easier to feel than a regular stone.. Some will argue a belt sander works great but the sanding belt comes away from the platen and actually make the cutting edge duller and I think the using of a belt sander is the stupidest idea I have eve heard. But what do I know I only taught Machine shop for 10 years at a community college.

[Cameron Wood]

If you buy a jobber drill out of a hardware store the drill point angle is a 118 degree included angle not 120. It is a 59 degree angle and not a 60. The other normal angle that it can come in is 135 included angle. I am sure one can get them in about any angle for special applications. Having said all that any angle close to that will work. The main points a to look out for are is that they are as close to the same angle as possible and the flute lengths are as equal as possible. I sharpen free hand but it does include a drill gauge. I like to stay at 59 degrees as closely as possible. It is easy to change angles when grinding and it is also easy to get one flute longer than the other. Hence the gauge which also has lines on it and I veneer the lines. Just so you know if drilling copper ,copper likes a single cutting edge not 2 so the drill point is drilled odd center with one flute longer that the other. Copper conducts heat very well and it can heat up and actually cease the drill bit.

Having said that steel on the other hand likes flutes of equal length. Also a drill of one flute being longer than the other will also drill a larger hole than the drill size That is where probable hole size comes into play

Now to sharpening. First of all you have to train your mussels so do not expect preface points right out of the gate. Place the drill onto the wheel ( eyeballing the angle of the point parallel to the grinding wheels face). I use 2 hands one top close to the wheel for support ad the other closer to the body . one closest to the body is dropped down and there is a twisting motion at the same time. Do not ride the drill point up the wheel but the grinding should be dun when the point is dropped. You can move it up and down the wheel but do not let it ride up always down. You will know when you are at the cutting edge because you should be see sparks come over the the cutting edge than drop the body hand and slight twist the drill at the same tine.

I bench grinder works best for this operation and the stones that come on the grinder will work but for me a 180 CBN wheel is ideal. Fine enough to get a good sharp edge but course enough to remove metal without heating the wheel. I find it easier to feel than a regular stone.. Some will argue a belt sander works great but the sanding belt comes away from the platen and actually make the cutting edge duller and I think the using of a belt sander is the stupidest idea I have eve heard. But what do I know I only taught Machine shop for 10 years at a community college.

Good info- I didn't know that about drilling copper. That's where I learned- community college machine shop. Didn't think highly of the instructor, 'tho- he spent almost all his time with the advanced students.
I think mussels would be very hard to train.

[Derek Cohen]

If you buy a jobber drill out of a hardware store the drill point angle is a 118 degree included angle not 120. It is a 59 degree angle and not a 60. The other normal angle that it can come in is 135 included angle. I am sure one can get them in about any angle for special applications. Having said all that any angle close to that will work. The main points a to look out for are is that they are as close to the same angle as possible and the flute lengths are as equal as possible. I sharpen free hand but it does include a drill gauge. I like to stay at 59 degrees as closely as possible. It is easy to change angles when grinding and it is also easy to get one flute longer than the other. Hence the gauge which also has lines on it and I veneer the lines. Just so you know if drilling copper ,copper likes a single cutting edge not 2 so the drill point is drilled odd center with one flute longer that the other. Copper conducts heat very well and it can heat up and actually cease the drill bit.

Having said that steel on the other hand likes flutes of equal length. Also a drill of one flute being longer than the other will also drill a larger hole than the drill size That is where probable hole size comes into play

Now to sharpening. First of all you have to train your mussels so do not expect preface points right out of the gate. Place the drill onto the wheel ( eyeballing the angle of the point parallel to the grinding wheels face). I use 2 hands one top close to the wheel for support ad the other closer to the body . one closest to the body is dropped down and there is a twisting motion at the same time. Do not ride the drill point up the wheel but the grinding should be dun when the point is dropped. You can move it up and down the wheel but do not let it ride up always down. You will know when you are at the cutting edge because you should be see sparks come over the the cutting edge than drop the body hand and slight twist the drill at the same tine.

I bench grinder works best for this operation and the stones that come on the grinder will work but for me a 180 CBN wheel is ideal. Fine enough to get a good sharp edge but course enough to remove metal without heating the wheel. I find it easier to feel than a regular stone.. Some will argue a belt sander works great but the sanding belt comes away from the platen and actually make the cutting edge duller and I think the using of a belt sander is the stupidest idea I have eve heard. But what do I know I only taught Machine shop for 10 years at a community college.

Thanks Tom. As you have written, 59 degrees is the angle when supplied. I chose 60 degrees for the jig as this is easier to measure. Plus, the wood cannot tell the difference. I am sure that when freehanding the drill but face on the grinder wheel, the angle will change slightly anyway.

I think the easy way to remember what to do when grinding (I trust my earlier correction of the photos did not confuse this) is to start with the cutting edge and then rotate the bit to grind the relief.

To repeat what I wrote at the outset ... this jig is to train the hand.

Regards from Perth

Derek

[Derek Cohen]

Years ago I was advised to increase the cutting angle (with a micro bevel) when cutting brass and copper. I do this with a diamond hone. It seems to stop the grabbing.

Tom, can you comment on this?

Regards from Perth

Derek

[Tom Bender]

A long time ago, as a young engineer working in a large manufacturing facility I saw a note offering a drill bit sharpening class. It was given by an old machinist on the midnight shift which meant coming in an hour early. I was the only student. We started with a 2" bit which made it easy to see and understand. It's been a lesson more useful than hundreds of calculus classes I've sat thru. Same with the welding class.

[Tom Trees]

I think I found AvE's video the most helpful, in regards to successfully showing the technique clearly, even with the comical angle grinder bodgery,
whilst also the most entertaining to boot.
Plenty of obscenities in this one, so some might want headphones.
https://youtu.be/FgcESWoJ3CU?si=C7l-2F96D9ZPs9Fh

[Tom M King]

I have one unusual circumstance for hand sharpening a drill bit. The blades I like for my mower don't come with a 3/4" hole that it requires. I buy them with 5/8" holes and drill out the hole. The Gator blades are hardened, which I found out the first time means the whole blade. I bought some 3/4" cobalt bits.

I put a 5/8 bit in the drill press, put it down through the blade hole, and clamp the blade to the drill press table. That leaves the enlarged hole centered, and the blade doesn't require much balancing.

I might get one hole until it breaks off the corners of the 3/4 bit even with plenty of lube. I probably have to stop 4 or 5 times to resharpen the bit to do three blades. I don't care about the angle, since I'm only using the outside 1/16 anyway. As the angle gets sharper, the better it cuts for this job. I guess I'm getting it closer to being a car reamer.

I have a 3/4" car reamer, but I'm afraid to use it on this hardened steel as it's much more valuable than a drill bit. Comments are welcome. I'm sure the other Tom knows about this. It's just guesswork for me.

I not only like these blades better, but they last at least twice as long and are $45 cheaper for a set of three mower brand blades. The $35 dollar bit is paid for in one set, and so far I've gotten three sets done with one bit.

[Steven O Smith]

Have you tried heating just the area you're drilling? Clean the metal so it is bright, heat until it turns blue, quench to keep the heat from getting to the blade edge.
It should be *lots* easier to drill.

[Tom M King]

That might work, but this only takes a few minutes including any bit grinding. Once in a while I can drill all the way through without having to sharpen the bit. My torch would require longer than that to dig it out from behind other stuff crowded in that shop. Right now, my mechanic shop is serving multiple purposes with the main purpose being tool storage. Into too many other jobs to build the other shops I need right now.

There are a number of things I could do to make this job quicker, but all take longer than the time to get it done like this. One set of blades lasts me a whole season here, which is about 50 hours with that mower.

[George Yetka]

Now you have to sell them.

[Steven O Smith]

Tom, have you tried heating just the area you're drilling? Clean the metal so it is bright, heat until it turns blue, quench to keep the heat from getting to the blade edge.
It should be *lots* easier to drill.

[Tom M King]

Steven, please read my last post. It's not hardened a lot, just enough to be more work than A36. It's only a few minute job as it is, and I only have three of them to do a year.

[Steve Demuth]

Brilliant.

[Paul Saffold]

Tom, have you tried heating just the area you're drilling? Clean the metal so it is bright, heat until it turns blue, quench to keep the heat from getting to the blade edge.
It should be *lots* easier to drill.

Quenching it will harden it.

[Steven O Smith]

Tom, sorry about the repost. My settings were wrong, which kept me from seeing my first post. I wrote it again--still couldn't see it and went over to the Tech Support forum. Now I see both!
Sounds like you have a working solution.

Steve