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handsharpening Drill Bits -- HOW??

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  • handsharpening Drill Bits -- HOW??

    any old fogies (ha, just kidding) out there
    know how to sharpen a drill bit by hand and CAN EXPLAIN IT TO ME??

    i go through more drill bits in a month than cups of coffee.

    i dont have a gauge, i dont have a machine.. what i have is a grinder and a LOT of dull drill bits.

    i wont even ask about endmills.

    -knucklehead.

  • #2
    Here's a link, scroll down a little.

    http://www.tpub.com/steelworker2/121.htm

    Mike

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    • #3
      That pretty well covers it. You really need a gauge as lip length and angle are very important. Find a new drill that has not been used or sharpened and compare your attempts to it to see what you need to do. I pretty much start with the lip horizontal and then sweep it up from there putting a little more pressure on as you go up for the clearance. Then practice, practice and then do it some more!

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      • #4
        The web site above is a good explanation but I have a cup of water that I go back to often to keep the drill cool. Just don't let it get too hot.

        Ever notice that a drill will chip at first or last a long time? I round the cutting edge after sharpening when drilling steel with a small stone by stroking it straight with the edge. Works much better.

        If the size of the drilled hole matters at all I will pre-drill the hole with a drill that is just a little bigger than the web of the finish drill. That way your finish drill is not using it's tip for a center, it is working more like a reamer. Even with a new drill you will get a more accurately sized hole this way. It also takes much less pressure to drill this way.

        Make test holes. Try the drills you want to use on a piece of scrap first. Surprises in machining are no fun.

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        • #5
          Easy.

          Take a buggered drill bit and grind it until it looks just like a new one.

          Now don't you feel stupid about the old fogey comment when you knew the answer all along but were not willing to admit you lack the ability to differentiate the subtle nuances between a "new" and "worn" twist drill other than "it don't work now"?

          Now, endmills - those are hard to sharpen. Make a Quorn Tool grinder. Sharpen end mills. Easy, but you won't have any hair left - don't say I didn't warn you.

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          • #6
            There is absolutely no way to hand re-sharpen drill bits for accurate hole drilling. Far too many variables involved in grinding the tip for anyone to be able to eyeball it even with a drill grinding gage.

            They CAN be sharpened by hand, but never accurately enough so the drilled holes will match those of factory sharpened bits. So, if accurate holes are needed buy a good quality drill sharpener.

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            • #7
              knucklehead: I finally broke down and purchased a "Drill Doctor". It actually works pretty well.Never could hand sharpen drill bits worth a hoot! Jim

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              • #8
                I've never seen the need to try to achieve that 'rounded' relief as on a new drill. Endmills, after all, have flat relief facets. Maybe I'm wrong, but I've been generally satisfied with my results... at least for drills larger than about 1/4". Smaller ones I have little luck with.
                Lynn (Huntsville, AL)

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                • #9
                  This has been covered before, but I'll air my views on it again:-

                  Before you can successfully attempt to hand grind a drill point you need to have a good true grinding wheel - freshly dressed and flat with good corner definition (between sides and rim). DO NOT USE A WHEEL which has just deburred a piece of 3 x 3 angle, ground a weld joint, or been subjected to similar abuse!!

                  Hold the base of the drill shank in the right hand as you would a small dial knob (between thumb uppermost and first two fingers underneath), with the left hand (thumb above and first two fingers underneath again) support the drill near to the end but leave enough margin from the wheel. Now present the drill bit edge to the wheel with the drill angled down and towards you ~ the drill cutting edge should be level but slightly high on the wheel (10 o clock position looking side on) ~ gently introduce the drill to the wheel maintaining these angles, as it sparks ~ lightly twist with the right hand, roll with the left hand, whilst lifting the point with the left hand (trying to 'feel' and follow the relief angle). The drill will need to be fed into the wheel to compensate for the lifting of the left hand, do this with the right hand by pushing (lightly) in towards the wheel. Repeat for the opposite side.

                  Check with a propietary drill gauge ~ or have a thin strip of suitable bright mild steel plate with a foot on it - blue up the face and with the drill resting on the foot scribe the blueing first with one edge then the other to check for equal lips. When using the drill for the first time after resharpening check for equal piggies tails of swarf off the two edges.

                  Practice, practice, and practice again and YOU CAN DO IT. Even practice the action without the grinder running, just give yourself the clearance to feel what it feels like! Many years ago when a machinist or fitter went for a job' success or otherwise, sometimes depended on a demonstration of one's capabilities of hand sharpening a drill.

                  Lynnl - don't you get a dragging relief at the back edge with a 'flat' grind? and how do you keep the drill from 'diving in'?? I agree that sub 1/4" takes some practice (or better glasses when you become an old fogey!!) - but I still manage down to mid #30's

                  Pat S - Beware plunging an over hot tool into water(!) it will give rise to cracking of the cutting edge. Try dressing the wheel with a good diamond ~ you'd be amazed how cleanly a freshly dressed wheel will cut - and without overheating the tool!

                  DR - I agree, but who ever heard of accurate hole drilling? That's what reamers were invented for!!

                  OFR
                  Old Fogey Raglan

                  [This message has been edited by Ragarsed Raglan (edited 02-26-2003).]

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                  • #10
                    One of the things that aggrevate me the most is to go to a grinder to sharpen a tool of anykind and finding that the wheels are all grooved up by someone not knowing how to use a grinder correctly. When grinding a tool or drill the most important thing is to have the wheel properly trued and dressed. You can't get a good edge on anything without a well dressed wheel.

                    Joe

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                    • #11
                      Raglan,

                      In my shop we drill accurate holes all the time. A good deal of our work is production CNC lathe work. Timewise we can't afford to add another operation of reaming to the part so the holes have to be drilled accurately. The accurate holes are especially important where we're using small diameter form taps.

                      I have a Darex SP2500 drill grinder and an SRD. Both do a good job and are easy to use.

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                      • #12
                        I spent 5 long sad years in a screw machine shop learning that I am JUST not good at setting up screw machines. We sharpened drill bits by hand all the time and got great results, (except me , see first sentence). Boss wanted some holes on size +.001-.000. I could never get any closer than .002-.003 which is why I make conveyor belts now. Seen other people do great job sharpening day in and day out, so I know it can be done, just don't ask me to show you how
                        mark costello-Low speed steel

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                        • #13
                          I agree with DR.....to a point....I have been grinding drills by hand for a long time...It is an art that is very hard to teach...I suggest that you practice and practice, and yes...practice..

                          When I sharpen my drills, I hold my arms in a weird triangular type position or something, i can't explain, but i try not to move when i switch from one lip to the other...this insures that i have the same angle on both lips...Nothing is perfect, but i do a lot of drilling on CNC's and manuals, and I have very goood results..Occasionally I have to re-grind the drill because of an oversize problem..but I can get it right atleast 90% of the time....

                          But, I really enjoy grinding drills..I don't know why I like it, I just do...its fun...If you hate sharpening them, then don't do it...Drills are cheap..just check any catalog...cheap...

                          brent

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                          • #14
                            <font face="Verdana, Arial" size="2">Originally posted by Ragarsed Raglan:
                            DR - I agree, but who ever heard of accurate hole drilling? That's what reamers were invented for!!
                            [This message has been edited by Ragarsed Raglan (edited 02-26-2003).]
                            </font>

                            Well, the reamer can't straigten the hole! to have an accurate hole, both size and c-c distanace to other holes, the tip of the drill needs to be ground in a fixture! Drills are precision tools!

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                            • #15
                              The sorry fact is that twist drills are not precision tools. At best, they make an almost round hole that is almost straight that is almost the size stamped on the shank.
                              As indicated above, a good machinist can touch up a drill to drill an accurate hole, or an oversize one if desired.
                              If it is accuracy you are striving for, start hole with center drill, and ream or bore it to final size.
                              Jim H.

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