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A quick path to grinding my brazed carbide tools

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  • A quick path to grinding my brazed carbide tools

    I have acquired what is probably a lifetime supply of brazed-on carbide tools, but have had no way to sharpen them. I got a diamond cup wheel and was going to build a table etc so that I could use it with a low speed motor I have. Someone in a recent thread (Doozer maybe?) suggested that you'd get a better finish at low speed since the tool bit would "bounce" on any irregularities on a high speed wheel. I may still do that, but last week I found a combination belt grinder/disk sander on the local buy-sell site for 30 bucks, and got it thinking that even a small belt grinder would be useful. Then, realizing that I did not really need a second disk sander got the idea to turn that part into a carbide grinder. I'm sure it does not work as well as one purpose designed for this, but I'm quite pleased with the edge I can now get on my carbide tools. This is a 1750 rpm motor, if I do get around to using the low speed (with a finer wheel probably) it's 85 rpm. I'm sharpening the angles by eyeball, like I do with my HSS.

    So I went from this:

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    to this:
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    Basically needed just an adapter from the 5/8" shaft to the 20mm mounting hole in the wheel, and cutting a chunk out to the table.

    Click image for larger version

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    "A machinist's (WHAP!) best friend (WHAP! WHAP!) is his hammer. (WHAP!)" - Fred Tanner, foreman, Lunenburg Foundry and Engineering machine shop, circa 1979

  • #2
    For $30 and some time, I think you have got one very useful tool there.
    Location: Saskatoon, Saskatchewan, Canada

    Comment


    • #3
      Ditto! Great job for $30.

      The main thing that most people don't know about diamond wheels is how to true them and how to keep them true. I have had years of experience making diamond tools using several different types of diamond wheels. And it took some time before I was able to reliably work the wheels and keep them true and flat.

      Good news is with carbide it's less difficult as it is softer than the diamond wheel. But let me pass on some tips:
      • Always try to grind carbide wet. Carbide dust is a serious health hazard and coolant helps keep the dust out of the air.
      • Use a dressing stick grit size that is close to the wheel grit size as possible.
      • Dress the wheel wet with the dressing stick pushed down on the table. Feed in till it touches the wheel and let the wheel remove the stick. That is push or clamp the stick to the table and feed with table infeed or slight bump of the hand, letting the wheel grind away the stick without letting the stick ride on the wheel. The idea is to let the dresser hit the wheel on the high spots only. This exposes new diamond on the high spots and over time the wheel will true itself.
      • Same tip on keeping the wheel flat. With the machine off, use a straight edge that spans the diameter of the wheel face to see if it is dished. Dress the high spots only, using the technique above. Then use the high spots as much as possible.
      Using these techniques over time will become second nature. When a wheel is true and flat, speed is less of an issue as the surface of the wheel no longer beats the work during use. And a smooth (true) wheel will give the best results on the carbide. It will grind the work quicker, wear slower, and last longer as more diamond surface contacts the work with each revolution.

      With a true wheel, the only speed consideration will be keeping the coolant on the wheel. Slower speeds will keep the wheel wet easier. Higher speeds will make the wheel appear harder to the work (a good thing). 1750 RPM is not at all too fast but will sling the coolant. I suggest a shroud around the wheel and a drip system to feed water or coolant from a coffee can, via a copper tube and small valve. Another method is to use a wet sponge against the opposite side of the wheel during use or dressing.

      Good luck with your new toy!

      Best Regards,
      Bob
      Last edited by rjs44032; 02-01-2021, 06:32 PM.

      Comment


      • #4
        This is one of those times that I wish I thought of that.... great idea!

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        • #5
          High speed produces heat and I have heard that diamonds plus heat burns the diamonds away. There goes your expensive diamond wheel. This seems to be a very good argument for using a high speed, diamond wheel wet to keep the temperature down. Possibly a good argument for slow speed for diamond wheels as well.

          I have a slow speed grinder with a non-diamond wheel. It has a built in water bath and it works well. The wheel seems to stay cleaner and I have no problems with overheating the objects being sharpened. I really like that. If I were to make or buy a machine with a diamond wheel, and I do need one, it would probably be both slow speed and have a water bath built in.

          If I am wrong, go ahead and blast away.

          And yes, the OP's repurposed grinder does look like a nice idea. Just use it wet.

          This reminds me that I need to sharpen the kitchen knives again.
          Paul A.
          SE Texas

          And if you look REAL close at an analog signal,
          You will find that it has discrete steps.

          Comment


          • #6
            Always try to grind carbide wet.
            Thanks for the tips!

            I was planning to add a drip system, but just got this far this morning and now have to find where I put the parts for it. It's a medical IV feed bag, tube and valve I got from a nurse friend, figgered it would fit for something like this. I have a water bath, slow speed knife type sharpener, but I didn't consider an actual water bath for this - is there any downside to this with a diamond wheel (other than at speed it's gonna spray all over...)?
            "A machinist's (WHAP!) best friend (WHAP! WHAP!) is his hammer. (WHAP!)" - Fred Tanner, foreman, Lunenburg Foundry and Engineering machine shop, circa 1979

            Comment


            • #7
              I like it !

              --D
              DZER

              Comment


              • #8
                Originally posted by Paul Alciatore View Post
                High speed produces heat and I have heard that diamonds plus heat burns the diamonds away. There goes your expensive diamond wheel. This seems to be a very good argument for using a high speed, diamond wheel wet to keep the temperature down.
                That is only when the diamond wheel is used on steel or iron. At high speed the diamond gets dissolved into the steel or iron as carbon and eaten away. For other materials (tungsten carbide tooling) speed is not an issue. Wet grinding is good no matter the material though.

                Comment


                • #9
                  I’ve been using a metallurgical disk polisher of late, fetched it home from the 5s purge, I’m just spraying the circular lap with cooling and going slow, seems to be working, as a bonus I’ve found it does a good job of wood chisels and plane irons, I must admit to getting sharpening disease, once I start everything gets sharpened, terrible affliction of trance like state and hairless arms.
                  brazed carbide is as good as I need to be fair, I don’t really machine enough to warrant tipped tools, they are handy but not strictly necessary, the diamond does a fair job of HSS too, well done on the sharpener, good idea, I found a diamond belt that fitted my belt linisher in a skip or dumpster at the local glass place, not tried it yet
                  mark

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                  • #10
                    May I ask where you got the wheel? Those things are high $.
                    Nice looking unit.

                    Comment


                    • #11
                      Originally posted by challenger View Post
                      May I ask where you got the wheel? Those things are high $.
                      Nice looking unit.
                      Shars (Discount_Tool ebay) has them for reasonable prices.

                      -D
                      DZER

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                      • #12
                        I like this, thanks for sharing!

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                        • #13
                          i have been grinding and honing carbide tools at 2800 rpm with resin diamond wheels dry for ages. never had problems with any runout. if the weheels were not true i would simply correct the aluminum body.

                          Comment


                          • #14
                            May I ask where you got the wheel? Those things are high $.
                            China by way of Amazon Canada, ~22 bucks : https://www.amazon.ca/gp/product/B01...?ie=UTF8&psc=1
                            Many of the sources in the US either won't ship here or the shipping makes it very ...um, unappealing.
                            "A machinist's (WHAP!) best friend (WHAP! WHAP!) is his hammer. (WHAP!)" - Fred Tanner, foreman, Lunenburg Foundry and Engineering machine shop, circa 1979

                            Comment


                            • #15
                              14.00 dollars on the US site with a 5% off with Prime for that wheel. Wow, cheap enough.

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