How to sharpen a drill with a bench grinder

Hey all,

I was hogging thru some steel parts last night and thought some of you here might benefit from knowing how to sharpen a drill with a bench grinder . . you'll never have to buy another drill again unless it get's too short . .. no you don't need one of those stupid fixtures or anything.

Let me know if you want pics and detailed explanation . . . it's one of the first things I have a guy do that thinks he knows what he's doing . .. a lot of people think you just send drills out to be sharpened . . . they'll cut better when professionaly sharpened 'cause the angles are perfect but when you have a dull drill and are in the middle of a job it's amazing what just hand sharpening by eye on a bench grinder will get 'ya . . . I've not had a drill sharpened "outside" in 15 years.


cheers

 

okay less than .100" is a PITA . . . for small drill bits you'll need some magnifying spectacles . .. you'll get good on like 1/4-1/2 pretty fast and gradually get better on the smaller drills .. . no suspense or secret . . I'll take some pics today and post pics .. . it's all about how you hold the drill to get the right releif angle and keeping the tip in the middle . . . just think it's something everyone should know that works on a car.


cheers

 

I'll show you some advanced chip clearing grinds that you can't do with those things

 

okay never mind go buy Drill Doctors

 

hee hee . . .clearing off my camera disk . . . got to figure how to shrink pic's on this new computer . .. should have 'em in a few

 

man thanks . . I had the f****** post all done and hit backspace or something and lost it . . one more time

 

explanation to follow
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Pic 1 shows a drill that's not that dull but the relief angle sucks . .. this is what most people don't do right.

Pic 2 & 3 shows how to hold the drill on the grinder to get the relief angle and point angle . . picture the relief angle being such that only the leading edge of the drill touches the metal when drilling

Pic 4 & 5 shows an okay sharpening job with one relief angle

Pic 6 shows second relief angle

Pic 7 shows third relief angle

Pic 8 shows how I could've ground a bit more off the tip . . still some metal transfer/lack of edge

Pic 9 shows a top of the line drill with the 3rd relief angle ground all the way to the point . .. think this is what they call "split point" . . start with just a single relief angle first .

Good luck and wear safety glasses.

 

start with a 1/2" drill that still has some shape so you get the feel of how to hold and move the drill on the grinder . .. it really should feel quite natural

 

that grinder's a bit coarse but it gets 'er done . . you can do this in the field with an angle grinder . . you hold the drill to the angle grinder though unless the drill is like 2" or something

 

the drill point angle was a little "pointed" in the first pic . .. I flattened that out as I ground it . .. when you just do a quick dress/resharpen the drill point angle has a tendency to get steeper 'cause it's the outer edge that wears the fastest (hotter).

 

yep that'll work . . figured more people have bench grinders kicking around . . . I've got a box of those course rocks I'm trying to use up

I guess the thing about a tool like that drill doctor is if you know how to check if it's doing the right job, then really you should be able to sharpen them by hand anyway. We had one years ago and one of the engineers decided to sharpen a bunch of drills . . he just screwed them all up because someone had messed up the rock on it and because he didn't know what a sharp drill was supposed to look like he didn't know what a screwed up one looked like either . . . but as is so common in the world today . . . he just hoped the $100 tool would allow him to not think or pay attention .

 

I got my engineering degree in the U.S. . . . during college a common theme was don't worry about how to make it . . .someone else will worry about that . .. I don't think they train engineers in Europe like that do they? . . guys over there please respond . . . what is it like to get an engineering degree over there? Do you still do a bunch of hands on?

I have seen a lack of mechanical aptitude with scores of engineers . .. I really get a kick out of the ones that are so green they think everything can just be modeled on a computer . . .press a button and bang . .. a CNC will just make it . .. they are training guys this way with all this new modeling software and these guys think a guy running a Bridgeport is in the stone age . . I guess it's good that they're so confident and green that they're pretty open about how they think the manufacturing world works . . which then immediately gives me an indicator of what I'm dealing with .. and I take the shop floor attitude with 'em.

"you can do all that on a Bridgeport?" . .. . short of keller cutting 3d molds there's nothing you can't do on a Bridgeport/Prototrak . . it's all about tooling.

cheers

 

if you want exact bore dimensions you should use a boring bar or a reamer . .. on the lathe or mill . .. when you're talking exact you mean less than .001" right? . . the surface finish from a drill I don't think warrants ever trying to hold a real tight tolerance.

cheers