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Grinding lathe tools - small concave form / radius

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  • Grinding lathe tools - small concave form / radius

    I've got two B'port heads but only one functional Trip Handle I could buy a new one for $28 with shipping but I figured I'd bore out the tip and silver solder in a shop made ball stud. I plan to use a SHCS for my ball stud stock.

    How does one grind small concave features such as the tool in the image. For HSS, I'd use an abrasive disc in a die grinder. What would one use on a brazed carbide tool to grind a small pocket? My 1 inch wide green grinder wheel won't get me to a small concave form. I have lots of chipped brazed carbide lathe tooling bought when a local HS closed the machinist program and I would like to have several preground lathe tools on hand for future use as well as the immediate project.

    Sent from my 5049W using Tapatalk

  • #2
    Diamond grinding wheel.

    Traditionally crazy expensive but recently the chinese diamond grinding wheels have changed the market. Ex soviet countries also sell old soviet era stocks or new Ukrainian products.
    Available from Shars/ebay/aliexpress/amazon, pick your poison.

    ie.
    https://www.ebay.com/itm/Diamond-Gri...EWGfa7yiX7aeJA
    or Ukrainian ones:
    https://www.ebay.com/itm/125mm-Hole-...IAAOSwjONZbc9h

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    • #3
      Diamond lapidary saw blades also work if you need really tiny features in carbide. (like 0.01" slots)

      https://www.ebay.com/itm/5pcs-4-5-11...MAAOSwPtBcdeWz

      Just don't expect the lapidary saw blades to last long, in my (very limited) experience the lapidary saw blade is toast after going twice trough 1/4" round carbide shank.
      Proper coolant and moderated feed force could help.

      Comment


      • #4
        Grinding requires diamond abrasive. You can get a diamond burr for your Dremel. They go for about $20.00 ea. with a 3/32 shank. https://www.riogrande.com/product/di...bur-set/343010

        The only other method is EDM. If you know someone, good. Go for it.

        RWO

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        • #5
          My interpretation is that you want to change the brazed carbide tool on the left to have a pocket where the carbide currently is. Furthermore you want a gentle radius such as you have on the middle tool.

          The easiest way is to remove the carbide (using heat ) and then mill a flat using the side of an endmill. Pick your endmill to match the radius that you want.

          Dan

          EDIT: AFTER READING PAUL'S POST #10. IT APPEARS THAT THIS POST IS 1000% WRONG. THE OBJECTIVE SEEMS TO BE MAKING A FORM TOOL FROM THE BRAZED CARBIDE ON THE LEFT
          Last edited by danlb; 08-12-2019, 02:54 PM.
          At the end of the project, there is a profound difference between spare parts and extra parts.

          Location: SF East Bay.

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          • #6
            Originally posted by danlb View Post
            My interpretation is that you want to change the brazed carbide tool on the left to have a pocket where the carbide currently is. Furthermore you want a gentle radius such as you have on the middle tool.

            The easiest way is to remove the carbide (using heat ) and then mill a flat using the side of an endmill. Pick your endmill to match the radius that you want.

            Dan
            Wouldn't the easiest way be to just use the other end of the tool?

            RWO, I've seen really cheap sets of diamond point bits at PA but I've wondered just how good (or bad) they would be. So far I haven't had any need for them so I haven't spent the money just to satisfy my curiosity.

            https://www.princessauto.com/en/deta...et/A-p8535569e
            Location: Saskatoon, Saskatchewan, Canada

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            • #7
              Originally posted by Arcane View Post
              Wouldn't the easiest way be to just use the other end of the tool?

              RWO, I've seen really cheap sets of diamond point bits at PA but I've wondered just how good (or bad) they would be. So far I haven't had any need for them so I haven't spent the money just to satisfy my curiosity.

              https://www.princessauto.com/en/deta...et/A-p8535569e
              I have used similarly priced diamond burrs from ebay-aliexpress and they work okay-ish on carbide. One was enough to grind small boring bar out of 1/8" round stock carbide and it looked like it has still life left.
              Use high rpm and very light grinding pressure/feed or the tiny tool is going to lose all the diamonds.

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              • #8
                Originally posted by MattiJ View Post
                I have used similarly priced diamond burrs from ebay-aliexpress and they work okay-ish on carbide. One was enough to grind small boring bar out of 1/8" round stock carbide and it looked like it has still life left.
                Use high rpm and very light grinding pressure/feed or the tiny tool is going to lose all the diamonds.
                Thanks for that info.
                Location: Saskatoon, Saskatchewan, Canada

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                • #9
                  You need ONE new ball handle? Why not just cut the ball by eye and file to shape by eye? Or if you must have it be a specific size to match make a little template that you can hold in a mag base arm just behind the stock and machine steps in the stock to rough form the basic ball and then file to shape and check the progress repeatedly with the template.

                  Or if it's something you'll want to do again a few times then what is wrong with HSS, slow RPM and lots of cutting oil? It's not like you're making dozens of the things.

                  If you really insist on grinding out brazed carbide bits then roughing the shape out with a finer grit masonary disc held in a bench grinder will remove much of the material. But it tends to chip the edge a bit. So rough it with the disc in the bench grinder and then cut back past the chipping and finish to shape with diamond burrs in a rotary tool like a die grinder or Dremel.

                  And yeah, I tried grinding a carbide tool with my tile saw as an experiment. It worked well enough but the masonry blade is fairly coarse and there was some small chipping that extended back around 10 to 15 thou behind the edge even when used with a light touch. So it's a cheap and easy roughing option but no good at all as a finishing or one stop shaping trick.
                  Chilliwack BC, Canada

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                  • #10
                    AIUI you want to use the tool on the left as a ball turner to reproduce the tool on the right to function as the unbroken one in the center. As suggested above, diamond burrs are less than a dollar apiece from Banggood and AliExpress, so that should do it. But I think you could also use a standard lathe tool in a ball turning jig to do it, although I've never done it. I believe this is the part you are trying to make:

                    https://www.ebay.com/itm/400574218935



                    You might also be able to use a steel ball fastened to the end of the handle:
                    https://www.mcmaster.com/balls

                    Or possibly a miniature ball joint as used in model cars and such:
                    https://www.ebay.com/itm/XTM-XTM3818...g/264285928769



                    Fixture balls might also work:
                    http://www.jergensinc.com/fixture-balls-plain-shank



                    There are also many ball joint assemblies, such as those on gas springs, that might be used.

                    As for ball turning attachments, here's one of many simple DIY tools:

                    http://pauleschoen.com/pix/PM08_P76_P54.png
                    Paul , P S Technology, Inc. and MrTibbs
                    USA Maryland 21030

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                    • #11
                      I have been having fun grinding lathe tools like this using cheap diamond wheels and burrs in my CNC. I have also been using it with a 4th axis to make special milling cutters from standard ones. With diamond there isn't a ton of grit going all all over like abrasive wheels.

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                      • #12
                        Can not easily be done by hand, controlling the tool to produce an accurate radius/arc on a form tool will prove difficult at best.

                        Off Topic
                        This is how a convex or concave radius is produced in an ancient 1996 CNC lathe, this happens to be a concave radius for a rope sheave, turning a ball is just as easy.


                        A finished ball.


                        You may make any size radius that you have small enough tooling for.
                        The canned cycle on this machine will not turn a ball in one shot for some reason so it takes 2 canned programs, one from the end to 1/2 way and another from 1/2 way to the back, go figure.

                        The canned cycle code looks like so for a 1 1/2" ball.

                        Tool width .125
                        nose radius .062
                        Program 1
                        Start X 0.000 Z 0.000
                        Line move X 1.500 Z -.75 Radius .750
                        Line move to the Max stock diameter if larger then 1.500
                        Roughing cycle
                        DOC .050
                        Feed .012
                        Finish cycle
                        DOC .005
                        Feed .004
                        End Program
                        Program 2
                        Start X1.500 Z -.75
                        Line move X 0.000 Z -1.500 Radius .750 ( this will cut the ball off leaving a nub from parting"
                        Same DOC and Feed rate. You tell the control the shape of the part and it generates the G-Code for you just like CAM.

                        Easy as pie, less then a dozen lines entered, any person with manual lathe experience could learn to program canned cycles in short order which are most of the routines a hobbyist will ever need.
                        The bad news is that such a control alone will cost several times what a small hobby lathe costs, such a Fanuc, Mazatrol and Hardinge. I suspect that this is why many low priced CNC machine manufacturers use Mach 3.

                        Do not be afraid of CNC, you probably did not know how to use a lathe when you started, same thing using a different method of control (-:
                        Last edited by Bented; 08-12-2019, 10:47 PM.

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                        • #13
                          Originally posted by BCRider View Post
                          You need ONE new ball handle? Why not just cut the ball by eye and file to shape by eye? Or if you must have it be a specific size to match make a little template that you can hold in a mag base arm just behind the stock and machine steps in the stock to rough form the basic ball and then file to shape and check the progress repeatedly with the template.
                          Say what?

                          At minimum you need TC grinder project + internal/external radius grinding jig +probably diamond wheel balancer project
                          Probably leads to building oscilloscope + adjustable bandbass filter for the dynamic balancer and ....

                          Ball handle? who needs it after that?

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                          • #14
                            The old time toolmakers I knew would simply take an old flat file, heat to red to soften it, drill or mill the required radius/shape, putting the hole it at an angle to get some cutting angle, then reharden and temper. Job done in an hour. I've done it myself and it works. You are not going into production with these after all, just want to do one or two?
                            'It may not always be the best policy to do what is best technically, but those responsible for policy can never form a right judgement without knowledge of what is right technically' - 'Dutch' Kindelberger

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                            • #15
                              Richard, I like your thinking. This would be particularly good for a small size like the one shown on that control piece.

                              Of course now Mattij's anti simplicity rant will be focused on you too....

                              ..... now where did I leave that bandpass filter and fragulator bracket........
                              Chilliwack BC, Canada

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