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How to sharpen a drill with a bench grinder

Discussion in 'Technical Q&A' started by luckydynes, Aug 13, 2008.

  1. luckydynes

    luckydynes F1 Rookie

    Jan 25, 2004
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    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
     
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  3. Fast_ian

    Fast_ian Two Time F1 World Champ

    Sep 25, 2006
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    Ian Anderson
    OK, so please don't keep us in suspense - Pix and details...... I do have one of those "stupid jigs" - crap IMHO. I can put some kind of tip on a dull drill with the grinder, but it ain't pretty. BTW, I'm particularly interested in small (say <1/8") bits - I've usually just bought a pack of 50 and considered 'em disposable.....

    Cheers,
    Ian
     
  4. luckydynes

    luckydynes F1 Rookie

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    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
     
  5. UroTrash

    UroTrash Three Time F1 World Champ
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    Jan 20, 2004
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    Not the answer you are looking for but I bought a Drill Doctor for $115 and it sharpens every twist bit I have easily. Works beautifully.


    http://www.drilldoctor.com/
     
  6. luckydynes

    luckydynes F1 Rookie

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    I'll show you some advanced chip clearing grinds that you can't do with those things :)
     
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  8. Lawrence Coppari

    Lawrence Coppari Formula 3

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    ditto
     
  9. luckydynes

    luckydynes F1 Rookie

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    okay never mind go buy Drill Doctors ;)
     
  10. Fast_ian

    Fast_ian Two Time F1 World Champ

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    No, no! - How many drills have you gotta sharpen to pay for the damn thing? I want to do it by "hand"......
     
  11. luckydynes

    luckydynes F1 Rookie

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    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
     
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  13. ferraridriver

    ferraridriver F1 Rookie
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    Go to Microsoft power Toys. Download “ImageResizer.exe” . A free app. That resizes pictures

    http://www.microsoft.com/windowsxp/Downloads/powertoys/Xppowertoys.mspx

    All you do is right click on any picture and select the size you want, small works fine for this site.

    It stores a small copy in the same folder the picture came from.
     
  14. luckydynes

    luckydynes F1 Rookie

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

    luckydynes F1 Rookie

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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.
     
  16. luckydynes

    luckydynes F1 Rookie

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    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
     
  17. luckydynes

    luckydynes F1 Rookie

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    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 :)
     
  18. luckydynes

    luckydynes F1 Rookie

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    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).
     
  19. ferraridriver

    ferraridriver F1 Rookie
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    Man, that stone looks rougher than my driveway :D :D

    I've found I get better results with my vertical belt sander and it's easier to see what I'm doing.

    I've tried the Drill Doctor, didn't like it, rather do it myself by hand
     
  20. luckydynes

    luckydynes F1 Rookie

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    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 :).
     
  21. 350HPMondial

    350HPMondial F1 Rookie

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    #19 350HPMondial, Aug 13, 2008
    Last edited by a moderator: Sep 7, 2017
  22. ferraridriver

    ferraridriver F1 Rookie
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    We had a giant magnetic base drill motor and one of the engineers decided to use it one day, I gave it to him, but surreptitiously flipped the reverse switch, He ruined several drill bitts getting nowhere before he figured it out. Gotta love engineers for giving you a good laugh :D :D
     
  23. Lawrence Coppari

    Lawrence Coppari Formula 3

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    Sounds like the enlisted versus officer thing to me.
     
  24. Martin308GTB

    Martin308GTB F1 Rookie

    Jan 22, 2003
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    if you want exact bore dimensions ( diameter ) the hardest thing with hand sharpened drill is to achieve, that both edges have exactly the same length and that the chisel edge is exactly centered. Otherwise you will always get a bore with a diameter twice the longer edge.
    During my mechanics education prior to my studies we exercised sharpening drills two weeks long.
    One can check this with a sample bore. If the bore gets bigger than the nominal dimension of the drill, the edges are of different length.

    Best Regards from Germany

    Martin
     
  25. luckydynes

    luckydynes F1 Rookie

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    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
     
  26. luckydynes

    luckydynes F1 Rookie

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    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
     
  27. ferraridriver

    ferraridriver F1 Rookie
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    I've got a Bridgeport, wish I had the knowledge, skills, and training to take full advantage of it, but it does make a damn nice drill press :)

    +1
     

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