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  • drill sharpening

    Is there a rule of thumb as to how small a drill is that can be sharpened by hand on a bench grinder. I always thought 6mm was kind of the limit but I sharpened a 4mm drill tonight because I needed to finish a job. It seems that as the drill gets smaller it gets harder to put on clearance.I saw somewhere that a guy made a jig for small drills and used an oil stone instead
    Please I come from a civilized country so dont talk to me in fractions or thousands as I just dont understand them
    .Regards eugene
    Last edited by plunger; 04-06-2011, 06:07 PM.

  • #2
    I'd offer some insight, but I'm afraid my uncivilized speech would only serve to confuse one such as yourself.

    But, let me offer this, so as to ease your suffering when dealing with the less civilized

    to convert metric to inch, multiply by .03937
    to convert inch to metric multiply by 25.4


    cheers
    Last edited by Walter; 04-06-2011, 06:22 PM.

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    • #3
      Plunger,, yes somewere there is an article about a guy using a jig and an oil stone to sharpen small drills,,, i have seen it, sorry i cannot remember now were it was. Hopefully someone here will come up with that article.

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      • #4
        Thanks walter I knew the 25.4 conversion but not the .03937 one so it just shows how usefull a sight like this can be. Now do you want to throw a figure at me as to how small a drill is that can be sucsessfully sharpened on a bench grinder. Then I get to use your formula to bring it to a respectible and understandable measurement

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        • #5
          Originally posted by plunger
          Thanks walter I knew the 25.4 conversion but not the .03937
          Probably because it does not work. I don't where it originally came from but if you use 0.03937 you will end up with an inaccurate figure

          metric figure divided by 25.4 = imperial figure

          eg 25.4mm divided by 25.4 = 1 inch

          12.7 divided by 25.4 = 0.5 inches

          -------------------

          12.7 X 0.03937 = 0.499999
          Precision takes time.

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          • #6
            My rule of thumb:
            If I can see it, and hold it, I'll try to sharpen it.
            I use a head magnifier, and sharpen down to ~2mm without other aids. Smaller requires a pin vise, and usually I use a single facit. I have sharpened 0.5mm diameter drills by hand. (With a little trial and error.)
            DJ

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            • #7
              I can't answer your first question as I don't sharpen drills freehand, but for the second, this is one site that may help those who were wondering about repointing very small bits. Personally, I use 2 mm a lot and I just thrown them out when they get blunt. A bit wasteful I guess and maybe I should one day look at something like this jig, as the results he's getting look excellent in the photographs. John has a good site and he describes things well.

              http://www.gadgetbuilder.com/DrillSharp.html

              Pete

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              • #8
                The .03937 looks suspiciously like the inches per meter value, 39.37, that I learned as a kid. I guess it was a close aproximation. I'd never really checked that out.
                Oh well, guess I should've grown up in a civilized country.
                Lynn (Huntsville, AL)

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                • #9
                  Originally posted by .RC.
                  Probably because it does not work. I don't where it originally came from but if you use 0.03937 you will end up with an inaccurate figure

                  metric figure divided by 25.4 = imperial figure

                  eg 25.4mm divided by 25.4 = 1 inch

                  12.7 divided by 25.4 = 0.5 inches

                  -------------------

                  12.7 X 0.03937 = 0.499999
                  can you measure .000001" ?
                  where it came from 1mm/25.4=0.0393700787401575

                  1000mm/25.4=39.37007874015748 "


                  1000mm*.03937=39.37"



                  so yeah your figure may be a little inaccurate, but unless you are plotting a course to the moon, you will probably be fine for most hobby sized measurements.

                  I prefer using 25.4 because it is faster to type.

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                  • #10
                    Originally posted by mochinist
                    can you measure .000001" ?
                    That is not the point, the point is 0.03937 is wrong..
                    Precision takes time.

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                    • #11
                      Originally posted by .RC.
                      That is not the point, the point is 0.03937 is wrong..
                      but close enough...if you're uncivilized anyways

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                      • #12
                        Am I missing something? Using your example 12.7 x .03937=0.4999999999 which is close enough to half inch to not be wrong in my book. All he is referring to is the reciprocal of using 25.4 which is 1/25.4 = .0393700784 to be exact. I can't offer much help as I have a Darex to sharpen my drills which will do 1/16" which unless my my math is wrong is 1.5mm.

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                        • #13
                          Drikk Grinding

                          Originally posted by plunger
                          Is there a rule of thumb as to how small a drill is that can be sharpened by hand on a bench grinder. I always thought 6mm was kind of the limit but I sharpened a 4mm drill tonight because I needed to finish a job. It seems that as the drill gets smaller it gets harder to put on clearance.I saw somewhere that a guy made a jig for small drills and used an oil stone instead
                          Please I come from a civilized country so dont talk to me in fractions or thousands as I just dont understand them
                          .Regards eugene

                          With care (and maybe a magnifying headband) you should be able to get down to 1 mm! Anything smaller, its easier and cheaper to buy them by the (dozen) packet.

                          NzOldun

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                          • #14
                            .03937 was the way I was taught when I moved to a shop that ran metric prints regularly. I've avoided the metric system because it's not what I was taught in school.
                            I look at something and can judge yards, feet, inches and fractions easily. Converting to decimals is almost completely automatic.

                            I honestly never questioned .03937, but after looking at it i can see the discrepancy. I am not, and never will be a math wiz but the reality is that something doesn't jive.
                            1/25.4=.03937
                            .03937x25.4=0.999998

                            As for small drill bits, I don't personally sharpen anything I can't see well, meaning anything under 1/8 inch gets the Darex. When I worked for the knife company, we used thousands upon thousands of bits 3mm and under, those always got sent out for sharpening. We weren't equipped to do mass fixes like that.

                            Plunger, and others; without excuses I was in a bad mood and looking to pick a fight. My apologies to all for that. I'll try not to let it happen again.

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                            • #15
                              Originally posted by .RC.
                              That is not the point, the point is 0.03937 is wrong..
                              My Lathe is imperial but I mostly turn to metric dimensions,so When I'm nearly down to finish size I use 0.03937 times the amount oversize to know how far to turn the dial infeed.

                              eg...

                              Need 6mm and measure 6.14mm.
                              Multiply 0.14 by 0.03937 gives....0.0055118"
                              Divide 0.0055 by 2 and that's the infeed on an imperial dial.

                              Allan

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