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Thread: So, how do you sharpen a drill bit?

  1. #1

    Question So, how do you sharpen a drill bit?

    I imagine this is an impossible task on a BBS, but how do you suggest I learn to sharpen drill bits?

    I have a KO grinder and do not know how to use it to sharpen drill bits. I have used it to sharpen HSS lathe bits by hand (with 50/50 success per the SB "How to run a lathe" book) but I do not know the critical parameters for sharpening drill bits or milling cutters.

    A reference as to what angles/reliefs are critical may help me or others. I really want to be able to maximize the life of my tools, even if it isn't cost effective. My hobby time doing anything in the shop can be counted as zero dollars! It helps make me sane!

    So, how do you re-grind a drill bit? Also, is it worth re-grinding the generic Chinese bits or should you only start with quality stock?

    Happy New Year!

    Sandy.

  2. #2
    Join Date
    Oct 2004
    Location
    Ellaville, Ga
    Posts
    1,356

    Post

    I think the angle is 60 deg. but I never check it. Just make sure the sides are the same length (Cutting edge) and the angle is the same on both sides. You also don't want the heel to drag. Think clearance on lathe tools. You sort of rotate the bits while grinding. I'd practice on something about 3/8 so you can see what your doing. Use a sharp rock too. I do it all the time on a bench grinder.

    ------------------
    Hoffman in Warner Robins Ga
    Techno-Anarchist

  3. #3

    Post

    If I got it right first time,everytime....I\'d have a real job!

  4. #4
    Join Date
    Mar 2001
    Posts
    674

    Post

    Sandy,

    Take a look here:

    http://yarchive.net/metal/drill_grinding.html

    It's an archived thread from rec.crafts.metalworking on sharpening drill bits featuring bits of wisdom from Robert Bastow, aka Teenut (RIP). Thw whole thing is a good read, but the meat is from a post he made on 10/11/99, about 2/3 of the way down the page.

    It would have been interesting to hear Forrest and Teenut debate a topic or two.

    Mike
    Mike Henry near Chicago

  5. #5
    Join Date
    Jan 2003
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    Utah
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  6. #6
    Join Date
    Jul 2002
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    3,890

    Post

    A bench grinder is the preferred tool for regrinding drill bits by hand. Read the above archives and find a coffee can full of dull bits and have at it( it may take two coffee cans full, but once you have aquired the knack you won't do it any other way)

  7. #7
    Join Date
    Oct 2003
    Location
    Richmond, VA
    Posts
    154

    Post

    The most important points are:

    Keep the point in the middle! Take a little more off the short side if needed in order to recenter.

    The flat on either side of the end should tilt back a little from the cutting edge to provide relief.

    I like the 1-piece gage for checking angles (and centering). A look at a pic of one in a catalog or textbook should give you enough info to make one, if you wish.

    Definitely start grinding on your cheapest drills first, they're gonna get shorter when you're learning. Once you understand the principles, sharpening is easy.

    Have fun,
    BillB (who started sharpening on drills about #65-#70)

  8. #8

    Post

    For all questions you should start by refering to Machinery's Handbook as there's a lot of info in there. It will at least give you the geometry and what it should look like when finished. When I started in the trade I spent many hours poring over the dry, boring details of cutting tools but it gave me guidelines for how things were supposed to be done. Relief, primary and secondary clearance and rake are all things that should be strived for by numbers more than by eye. My tooling doesn't always get done to the ideal numbers either but I keep the numbers in my head when I'm sharpening by hand. Use a solid drill gauge, step drill to final diameter, and practice. But remember that practice does not make perfect unless you use perfect techniques. Practice bad habits and it only makes them permanent, just like my bad spelling.

  9. #9
    Join Date
    May 2003
    Location
    52N 122W Western Kanuckistan
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    Post

    My favorite sharpening technique these days is to buy them on half price sales...
    Free software for calculating bolt circles and similar: Origin now settable to bottom left! All values positive. Click Here

  10. #10
    jfsmith Guest

    Post

    Evan,

    I am with you on buying them at half price sales.

    Jerry

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