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  • Mr Fixit, he's talking about the edges being the same length so the chisel tip is located right in the middle.

    They look like and are used like this image.

    Click image for larger version  Name:	twist drill gauge.jpg Views:	0 Size:	16.1 KB ID:	1878507

    I always found when doing this stuff freehand like the pros without enough money for a proper drill sharpener do that I had a bugger of a time getting the angle and length both right at the same time. I quickly became a believer in having at least a 60* fence on the grinder's rest to set the angle so I could work on just holding the right angle and touching off for the matching lip lengths.

    Along the way I got the middle cost Drill Doctor and for up to 5/16 it's the way I prefer. Bad reputations from others notwithstanding.

    For bigger stuff I used a fence for the angle for quite a while but a little time back I made a rig that helps with holding the two lips at the same position. I didn't post it because it needs to be re-done as a Mk II because everyone knows that the Mk I models always need changes. But it's worked out well enough on 5/16 and bigger that I can see it being a big help.

    But for the time being a fence on the grinder rest to at least hold the right angle and perhaps a magnifier hood for the poor operator's eyes along with one of the lip length gauges shown above and you can get some pretty good drill shapes that cut pretty evenly.
    Last edited by BCRider; 05-31-2020, 05:20 PM.
    Chilliwack BC, Canada

    Comment


    • Originally posted by BCRider View Post
      Mr Fixit, he's talking about the edges being the same length so the chisel tip is located right in the middle.

      They look like and are used like this image.

      Click image for larger version Name:	twist drill gauge.jpg Views:	0 Size:	16.1 KB ID:	1878507

      I always found when doing this stuff freehand like the pros without enough money for a proper drill sharpener do that I had a bugger of a time getting the angle and length both right at the same time. I quickly became a believer in having at least a 60* fence on the grinder's rest to set the angle so I could work on just holding the right angle and touching off for the matching lip lengths.

      Along the way I got the middle cost Drill Doctor and for up to 5/16 it's the way I prefer. Bad reputations from others notwithstanding.

      For bigger stuff I used a fence for the angle for quite a while but a little time back I made a rig that helps with holding the two lips at the same position. I didn't post it because it needs to be re-done as a Mk II because everyone knows that the Mk I models always need changes. But it's worked out well enough on 5/16 and bigger that I can see it being a big help.

      But for the time being a fence on the grinder rest to at least hold the right angle and perhaps a magnifier hood for the poor operator's eyes along with one of the lip length gauges shown above and you can get some pretty good drill shapes that cut pretty evenly.
      Care to post a photo of the fence? Thx

      Comment


      • Originally posted by Mr Fixit View Post
        Metal Butcher,

        Can you elaborate on the comment about the lips length? I do try and sharpen mine and do have the drill bit protractor to check with, but I'm not familiar with the lip comment.

        We can all learn from each others experiences.

        TX
        Mr fixit for the family
        Chris
        BCRider hit the nail on the head. It's definitely pretty tricky as he said. I tend to work the angle right on one side ignoring length entirely. Then I fix the angle on the other side and keep working it until the lengths are right. The angle doesn't need to be dead on, so long as both sides are even. It's easier to start with bigger bits.
        21" Royersford Excelsior CamelBack Drillpress Restoration
        1943 Sidney 16x54 Lathe Restoration

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        • Pretty much what you all said. That is the reason why I prefer to have drill grinders if possible. I can't sharpen them for crap, myself. Well, I can make them sharper but I know they still ain't right. If those lips aren't *exactly* the same, it'll cut all wonky and weird. And don't even get into 4-facet grinds.... this guy has a real good page about it, I think he wrote an article here years ago. I really recommend people read this guys page: https://www.gadgetbuilder.com/DrillSharp.html
          25 miles north of Buffalo NY, USA

          Comment


          • Wow guys,

            I appreciate the lesson in drill sharpening. Like me, you try to do it on the grinder or 1" belt sander and get ok results but Iv'e just focused on the angle not the lip, which tells me why they would drill from one side more or cut a less than round hole vs what a new drill bit would, I know none do it perfectly.

            Another project to the list, drill sharpener. Maybe the tool rest is first in order if BCRider can share his design.

            TX
            Mr fixit for the family
            Chris

            Comment


            • If the tip is ground slightly off-centre, the diameter of the hole drilled will be set by the longer edge. It will be over-size.
              I did once get some (cheap) drill bits from China which had this problem. They all drilled about 0.2 - 0.3 mm oversize - except right at the 'bottom' where the tip of the drill broke through through. Once the tip is not cutting, the drill follows the edges and the main profile, not the tip. So all the holes those drills made were oversize except for a step at the bottom!

              Our locally-made (Aus) Sutton drill bits are hard and sharp, but only too often they are slightly bent from poor heat treatment. In a CNC this means the tips wobble around, which really destroys positioning accuracy.

              These days, for any CNC work, I buy Dormer drill bits. Very often stub drills rather than jobber ones too. I don't regrind the drill bits used in the CNC; I just replace them. I do regrind some bits for bench use.

              Cheers
              Roger

              Comment


              • Originally posted by Mr Fixit View Post
                Wow guys,

                I appreciate the lesson in drill sharpening. Like me, you try to do it on the grinder or 1" belt sander and get ok results but Iv'e just focused on the angle not the lip, which tells me why they would drill from one side more or cut a less than round hole vs what a new drill bit would, I know none do it perfectly.

                Another project to the list, drill sharpener. Maybe the tool rest is first in order if BCRider can share his design.
                I'm making this tool grinder rest, it can be adapted to a variety of sharpening situations:
                https://www.cgtk.co.uk/metalwork/grinder/rest

                Comment


                • I have a KO Lee T&C grinder. Could this be used for drills? I mean I'm sure it could but I don't know what fixtures etc are needed?
                  Thx

                  Comment


                  • Originally posted by DennisCA View Post

                    I'm making this tool grinder rest, it can be adapted to a variety of sharpening situations:
                    https://www.cgtk.co.uk/metalwork/grinder/rest
                    OMG, as a KISS guy I am staggered by the number of parts! It's a matter of degrees of freedom I suppose, but still.

                    Comment


                    • Originally posted by challenger View Post
                      I have a KO Lee T&C grinder. Could this be used for drills? I mean I'm sure it could but I don't know what fixtures etc are needed?
                      Thx
                      The original grind on drill bits is a little bit complicated geometry that dedicated drill bit sharpeners have built in. Tool and cutter grinders usually anticipate a simpler geometry of a primary and secondary grind on a large variety of cutters. A T&C grinder can do a good job of putting a four-facet grind on drill bits, which will look different than they did originally, but can cut well.
                      .
                      "People will occasionally stumble over the truth, but most of the time they will pick themselves up and carry on" : Winston Churchill

                      Comment


                      • Originally posted by Bob Engelhardt View Post

                        OMG, as a KISS guy I am staggered by the number of parts! It's a matter of degrees of freedom I suppose, but still.
                        With this rest and the right attachment you can sharpen the spirals on end mills.

                        Comment


                        • A pretty hefty 20mm boring bar, made from a stainless bolt (I have quite a lot of these, picked up from a scrap yard) and accepts a round 10mm insert. In this case a threading insert. I put the screw on top so I could get the boring bar as deep as possible.





                          I feel a bit bad about milling flats on it, I should have made a proper boring bar holder but I was too lazy. This way I cannot retract it as much for maximum stiffness.

                          Comment


                          • Originally posted by DennisCA View Post
                            I feel a bit bad about milling flats on it, I should have made a proper boring bar holder but I was too lazy. This way I cannot retract it as much for maximum stiffness.
                            Could you not just carry the flats on further down the bar so you can reduce the stick-out when desirable?

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                            • I was too lazy to do that as well. I will probably do it later though to get more adjustment, since it's too late to put metal back on. Just kinda bugs me in retrospect.

                              Comment


                              • Challenger posted a new thread asking about grinding drills in something other than a drill grinder. I posted pictures and some description of the jig I made to that thread which you can find HERE.

                                Dennis, nice job on the bar.

                                What you need for this sort of bar is a round hole holder that is either split and closes up to hold the bar or which has a pair of wedging cotters to hold the bar. If you use an Aloris or other sort of quick change tool post they all seem to have a round hole holder available. Or you could make one. A simple block or a bigger than usual QCTP holder that you set up and drill then bore directly in the lathe ensures center height is spot on for the hole. Then you can use a center height tool setting gauge to set the rotation so the cutter is at the proper height as you tighten the bar in place.

                                Here is a picture showing the monolithic block option. You can easily see the split lines and the location of two of the clamping screws for the smaller side. Two more on the other side pinch the 1" diameter bar.

                                Not included here is a bar holder bushing I made from some 1" bar about 5 inches long with a 3/8 hole on one side and a 1/2" hole on the other to accept the usual brazed carbide boring bars and use them with this holder. But something similar or the same sort of thing done as a QCTP holder would mean you can leave your own bars round and allow you to extend and retract for minimal overhang.
                                Click image for larger version  Name:	fetch?photoid=1829116.jpg Views:	0 Size:	97.1 KB ID:	1878843
                                Last edited by BCRider; 06-02-2020, 03:46 PM.
                                Chilliwack BC, Canada

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