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Tool post grinder for drill bit sharpening?

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  • Tool post grinder for drill bit sharpening?

    I put together a die grinder that adapts to my lathe tool post. I'm wondering if mounting a drill bit in my Jacob's rubber flex chuck would allow me to sharpen the drill bits? Obviously I can set up the grinder for a 135 IA but I suppose I'd have to do the relief behind the cutting edge by hand. Seems like a good a good way to at least get the cutting lip lengths equal no?

  • #2
    Seems like an overpriced, low featured "tool grinder". How would you cut the relief for the cutting edge? It takes more than just the 135 or 118 point angle. I bought this one back in April: https://www.ebay.com/itm/183879361963#rwid It works good on bits up to about 1/2" but I haven't been able to figure out how to do my larger bits on it. (With supplied holder) I'm working on one of my tractors now but will get to grinding some end mills after that. I did a couple when I first got it and it works great if you take your time setting up for it.

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    • #3
      They make a gauge that you can use to get the angles and cutting length of the edges the same.
      Like a flat plate with the angles kinda thing.
      I like a 2" or so belt grinder to sharpen twist bits.
      The toolpost grinder and lathe is not the way to go. Not at all.

      --Doozer
      DZER

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      • #4
        it would let you get the lips near identical, an important bit of the process and why a tool grinder will do a better job of it than hand grinder. But seems a complete pita and you then have grind relief just up to the line. I would do them by hand as best you can with a drill gauge until a T&GC makes its appearance. I also like to minimize the amount of grinding in lathe, sometimes its the only way, but its a lot better to do that on a bench grinder on the other side of the shop imo
        in Toronto Ontario - where are you?

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        • #5
          These are the four choices (five?) for sharpening drill bits. Without additional tooling can folks offer which one I should try and utilize to help get better at off hand drill bit sharpening please? Click image for larger version

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          • #6
            dang, you're not short of abrasive options are you?! I use one of those cheap and cheerful Craftsman type grinders that work on the side of a bench grinder wheel. I split the tip first (hardest part imo) and then grind down the lips until they meet at the tip. I usually collect drills into a bunch first and then run through all of them. Doesn't take long and with a bit of fiddling gets you a good relief and even grind. Even works on drills up to ~3/4" with a bit of care, though I strongly dislike doing anything much smaller than 1/8" as they are fiddly as f.

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            • #7
              I have always and only ever sharpened drill bit by hand. Couple of reasons - 1) I don't have any fancier equipment, 2) That's how I first learned it, 3) With a bit of practice you can do an entirely acceptable job*, 4) A drilled hole is never going to be perfect, and by choosing the right size bit can always be "good enough". If you need better you ream it or bore it. If I drill a hole it is either for a bolt to go through, in which case there will be some non-critical clearance allowed, or for tapping, which in 99% of the cases also allows a certain amount of wiggle room with regard to exact size. High precision is for lathes and milling machines, not for drilling. Now of course, if your sense of craftsmanship would be offended if your drill bits are not works of art, I don't begrudge you that! Go for it!

              *Well, ok, not the teenie tiny ones, for some value of "tiny" given the age of your eyes...
              "A machinist's (WHAP!) best friend (WHAP! WHAP!) is his hammer. (WHAP!)" - Fred Tanner, foreman, Lunenburg Foundry and Engineering machine shop, circa 1979

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              • #8
                Hi,

                Used to sharpen #3MT shanked drills with an old mostly worn out lathe and a toolpost grinder. It worked OK mostly. I would add the clearances need by hand. So it does get done. And if it's what you got, you use it.
                If you think you understand what is going on, you haven't been paying attention.

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                • #9
                  Very cute tool-cutter grinder you have there.
                  Would be a good idea to try one of those already mentioned
                  Craftsman or General swing type drill bit sharpening attachments.
                  That way you can use the table to advance the tool.
                  Much better than using one of these with a bench grinder.

                  --Doozer
                  DZER

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                  • #10
                    How are you going to get your tool and cutter grinder to put a relief or a drop shoulder on the point?

                    A drill Doctor is your best bet.

                    JL ......

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                    • #11
                      Originally posted by JoeLee View Post
                      How are you going to get your tool and cutter grinder to put a relief or a drop shoulder on the point?

                      A drill Doctor is your best bet.

                      JL ......
                      Craftsman or General swing type drill bit sharpening attachment.
                      Harig and Hybco make relieving attachments also,
                      but I an assert that you home shop gerbils would choose
                      not to afford one.

                      -D
                      Last edited by Doozer; 06-02-2020, 01:54 PM.
                      DZER

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                      • #12
                        for a four facet grind i used to do this:

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                        • #13
                          otherwise you need this:

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                          • #14
                            You're well set up to use some manner of jig on either of the two grinders you have already. What machine is that in the second picture? The rest tables on it are what all bench grinders should have. That's a really nice grinder ! ! !

                            This started in the home made tools thread but it seems like a good place to continue this since it may run for a while. I mentioned I'd made a MkI drill sharpening jig for use with bigger drill bits. But it has a design flaw in the way the finger works that indexes the drill bit. So some modification or a new MkII is needed. For better or worse here's the idea.

                            So first off I started out using the typical small angle fence that comes with the tool grinder. This was a help because it let me set the angle and if I watched to keep the lip being ground "flat" to the table it did a good job of keeping the back relief on both lips the same. So I only needed to work the edges until I they measured the same.

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                            So that gave me the idea that if I had a simple jig which would hold the drill and used a little adjustable finger to "level" the lip being ground that this would make my life easier. And if I added some way to locate the drill so I could flip it over and it sat the same way and I had a way to control the feed into the wheel that I could index it and get both sides the same without a lot of fussing about.... and that's where the DSJ (Drill Sharpening Jig) MkI comes in....

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                            So "how does it advance into the wheel?" you ask? The guide bar that fits into the slot is tapered slightly. In the picture with my thumb holding the drill in place that end of the guide bar is about .015 to .02 narrower than the other far end which was dressed with a file to be a close but still easy sliding fit. This gives me some play that is used to advance the drill into the wheel face until it won't remove any more material.

                            The little finger that reaches in to set the lip so it sits at the right height to come out level after being touched up is the weak spot. When setting up to attach the two parts together I messed up and the nose of the drill saddle is sitting back off the stone more than I wanted. And of course I've dressed the stone a few times since then. And each time the jig's geometry gets worse by the amount of the dressing removal. I'd like to do a MkII version where the drill saddle can move back and forth to set the spacing to the wheel face. A while back I tortured the small finger of 1/16 welding rod that is soldered into the adjustment lever a little and it's better. But as the stone wears and gets dressed it will get worse with the finger needing to move down the flute as the drill protrusion needs to be more and more. Hence the need for a MkII version..... Or a CBN cup wheel....




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                            Chilliwack BC, Canada

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                            • #15
                              Continued.....

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                              Now when ground this way on a flat dish wheel or if a similar jig were used on the periphery of a wheel the heels of the end faces would be in danger of dragging. This jig does not re-create a conical grind such as the drills came with originally. But the heel isn't critical and after both lips are sharpened it is easy to freehand grind a little secondary relief angle to move the heel back far enough to avoid it being an issue. Here's a picture of the crudely but unimportant secondary relief angle ground by hand. It ain't pretty. Usually I'm a little more subtle and they look a bit nicer. But this back area doesn't have a role to play so it's just a matter of getting the back heel out of the way.

                              Chilliwack BC, Canada

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