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Conical vs facet drill sharpening - what's you're favourite method?

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  • Conical vs facet drill sharpening - what's you're favourite method?

    After scoring a large haul of quality used morse taper drill bits today I'm faced with a lot of sharpening work. Seems to be two popular ways of doing it, faceted and conical. The original grind on these is conical but I see many people promoting a 4- or 6-facet cuts on the drills as a better way to achieve a good grind.

    Which is the better method - or is it simply a matter of preference?
    Peter - novice home machinist, modern motorcycle enthusiast.

    Denford Viceroy 280 Synchro (11 x 24)
    Herbert 0V adapted to R8 by 'Sir John'.
    Monarch 10EE 1942

  • #2
    Grinding

    I think it depends a lot on what equipment you have to do the job with.
    I prefer a 135 split point for most things.

    Comment


    • #3
      Faceted points are easier. You can do them on a single lip cutter. They aren't quite as strong a cutting edge as a "conical" or radial relief though.

      The radial relief might need a fancier drill sharpening attachment. Unless you use of one of the cheapo type designed for use with bench grinders, but those kind aren't what would be termed precision.

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      • #4
        Heres a website I found when I was in a similar position to yours

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

        The site mostly discusses different machines for sharpening drills, but in the process touches on the advantages of the different methods.

        as for my two cents, as a daily sharpener of drills:

        1. Whatever method, always sharpen so the grind marks are perpendicular to the cutting edge.

        2. always relieve the web point on larger drills (>.5 in)

        3. if the drill is in bad shape, rough it on a bench grinder. (saves alot of dressing on the drill sharpener)

        Also, I've always had luck with conical points, thats what I put on all the drills I use and its quick. however I have heard that faceted drills, especially 6 facets, are superior when used in CNC machines, so it must have some advantages

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        • #5
          Originally posted by 70Chrgr
          Heres a website I found when I was in a similar position to yours

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

          The site mostly discusses different machines for sharpening drills, but in the process touches on the advantages of the different methods.

          as for my two cents, as a daily sharpener of drills:

          1. Whatever method, always sharpen so the grind marks are perpendicular to the cutting edge.

          2. always relieve the web point on larger drills (>.5 in)

          3. if the drill is in bad shape, rough it on a bench grinder. (saves alot of dressing on the drill sharpener)

          Also, I've always had luck with conical points, thats what I put on all the drills I use and its quick. however I have heard that faceted drills, especially 6 facets, are superior when used in CNC machines, so it must have some advantages
          Hi Neighbor,

          Thanks for the memory jog. I sharpened a 17/32 drill bit a couple of days ago that was broken off straight and it took a lot of grinding. I didn't think to bring it over to the belt sander and rough it in like I usually would have back before I retired.

          Sure can forget a lot in 5 years of retirement.

          My drill sharpening machine does have a 10 or 12 inch wheel, so it sharpens a lot of drills between dressing.

          Brian
          OPEN EYES, OPEN EARS, OPEN MIND

          THINK HARDER

          BETTER TO HAVE TOOLS YOU DON'T NEED THAN TO NEED TOOLS YOU DON'T HAVE

          MY NAME IS BRIAN AND I AM A TOOLOHOLIC

          Comment


          • #6
            Peter,

            I think toolguy has hit the nail on the head. It depends what equipment you have to sharpen the drill.

            I used to sharpen larger drill bits on a cincinnati monoset with facets. Only because the monosets don't have the ability to swing a drill bit. Or at least our cutter grind department never did it that way.

            I don't see where there would be that much difference in performance. Conical does seem like it would be stronger, but the cutting edge is likely to fail before the clearance area comes into play.

            Brian
            OPEN EYES, OPEN EARS, OPEN MIND

            THINK HARDER

            BETTER TO HAVE TOOLS YOU DON'T NEED THAN TO NEED TOOLS YOU DON'T HAVE

            MY NAME IS BRIAN AND I AM A TOOLOHOLIC

            Comment


            • #7
              One of the most obvious advantages of a 4 facet (split) point is that you have a point rather than a chisel tip to align with scribed lines and reduces the need for centre drilling as the tip won't skid. Whether this makes the drill actually cut better I don't know.

              For lathe work I always use a centre drill anyway so a split point is unnecessary unless that is the only one I have of that size.

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              • #8
                Read this article for a good understanding of drill pint geometry.

                http://www.icscuttingtools.com/the-c...t_geometry.pdf

                At work they cant understand how i can drill and tap M12 (1/2") in 12mm thick 316 stainless steel plate with a electric hand drill, everyone else who tries used conical drill points and work hardens the metal, I use split points.


                Steve Larner
                Last edited by SDL; 12-17-2011, 06:03 PM.

                Comment


                • #9
                  Originally posted by DickDastardly40
                  One of the most obvious advantages of a 4 facet (split) point is .
                  faceted does not mean it's a split point.

                  agree with Toolguy, it depends on what you have...I used to grind conical by hand until i got a T&CG, now its faceted for my 'good set' (twist drills that drill on size) and by hand for my roughers (misc box of twist drills ground rough and ready). There is no huge advantage to the faceted (vs some expensive drill bit grinder) except that its the easiest way to do so in a T&CG and produces drills that cut to a thou or two on size - the reason is the lips end up dead on the same length. it could also be argued you get a better finish (than say the bench grinder), hence better edge hence better cutting & tool life. You can also do 6 faceted - knocking off the corner where the tip meets the side, supposed to make the last longer i believe.

                  for those who haven't seen them, here's my set up of home made tooling for facet grinding drills. Basically the bits sit in the V block and the tooth rest is used to get it indexed just so. everything locked in place, grind, then flip, index second flute against the tooth rest and the second lip gets ground just like

                  V block (made it to fit a clamp i had so didn't make that part of it) block is casehardened and ground



                  tooth rest



                  in use with a larger drill bit - univise is also homemade



                  results



                  Its fun having luxuries like this but they're a long way from a must have. Take some crappy bit that came in the bottom of a box off stuff. Read up on grinding a drill bit and practice on the crappy bit. I bet before you grind it to a stub you'll be pretty good and sharpening a drill bit by hand!
                  Last edited by Mcgyver; 12-16-2011, 01:16 PM.
                  .

                  Comment


                  • #10
                    That's a nice tool McGyver - I had remembered seeing it but couldn;t remember where or by whom.

                    I've spent a good while today sorting through my haul. Many are ground very flat with a pimple and I understand these are for drilling structural steel - I'm going to grind all of these to a traditional drilling point. I've ground several hanfuls and I'm quite pleased with the results, though the four-facet seems to come out better-looking than the conical-ground bits. At least I'm getting the primary angle and lip lengths very consistant which I guess is the most important since that's the working edge.

                    Right now I'm shopping for grinder wheels. Mine are about half-worn but more than that I've found that they are too coarse or too soft a compound for putting a nice smooth grind on the tips, they also cut very fast which is frustrating me when trying to free-hand the secondary relief.

                    I have had a go at point splitting but only a couple of times and both have been pretty much total failiures. Have to look at that again another time.
                    Peter - novice home machinist, modern motorcycle enthusiast.

                    Denford Viceroy 280 Synchro (11 x 24)
                    Herbert 0V adapted to R8 by 'Sir John'.
                    Monarch 10EE 1942

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                    • #11
                      Mcgyver,, very impressive tooling !!!


                      Thanks for posting this, very nice!!

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                      • #12
                        I use a drill doctor for all my bits that fit. If they don't fit they get hand sharpened.
                        Andy

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                        • #13
                          Mcgyver have those items you built been posted in "Shop Made Tools" ?

                          They should be there if they aren,t .

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                          • #14
                            Originally posted by 70Chrgr
                            Heres a website I found when I was in a similar position to yours

                            http://www.gadgetbuilder.com/DrillSharp.html
                            I'm very psyched that John mentions that his slick 4-facet drill grinder is the cover article for the January and March 2012 HSM Magazines!

                            Very elegant design!
                            "Twenty years from now you will be more disappointed by the things that you didn't do than by the ones you did."

                            Comment


                            • #15
                              I use a system like this one. I bought the prism that actually holds the drill bit. The rest I made myself. I bought a crossslide/compound for a very small lathe and mounted the drill bit holder to it. The cross slide and compound have stops so I can set the depth of cut with a stop.

                              It works really really good. I can drill very accurate holes with the drill bits I sharpen on this.

                              I can also split the points quite easily by locking the prisim and using the compound to feed the drill bit in from the side to center.
                              http://www.conquestind.com/kaindl_drill_bsg20.php
                              How to become a millionaire: Start out with 10 million and take up machining as a hobby!

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