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Thread: Grinding lathe tools - small concave form / radius

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  1. #1
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    Default 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. #2
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    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

  3. #3
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    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.

  4. #4
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    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

  5. #5
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    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 at 02:54 PM.
    At the end of the project, there is a profound difference between spare parts and extra parts.

  6. #6
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    Quote 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

  7. #7
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    Quote 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.

  8. #8
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    Quote 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.

  9. #9
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    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.

  10. #10
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    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:


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