Can a steel ball be machined to a smaller diameter?
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    Default Can a steel ball be machined to a smaller diameter?

    I have a 2" diameter steel ball, let's assume it is a perfect sphere. Is there a machine or process that is relatively accessible (not too expensive or hard to find) that would reduce the diameter to maybe 1.9"? I'm thinking of a grinder, probably?

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    I dont have much to offer on this one. I would think it would be very difficult to reduce the size and maintain accurate shape.

    However, Bal-tec specializes in this. I would give them a call. I have had them quote some odd sizes for me in the past. Prices always seemed reasonable.

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    A key question is the required precision and surface finish.

    There is a technique for making wood balls that involves placing an open bottom box over a belt sander and letting pieces tumble to shape. I've always been curious to try it. This video covers it well, and I'd guess it would work for the diameter reduction of a steel ball.

    Vibratory abrasion and polishing also come to mind.

    Wooden Spheres on a Belt Sander - YouTube

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    My recollection is that there's a scientist who created the smoothest spherical surface in the world. Basically by polishing and re-polishing an existing sphere on an apparatus that was simply a precision ring imbedded with lapping compound.

    Would take forever, but theoretically possible at little cost (except for time).

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    Pretty Cheap to just buy the size you need IMHO

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    Thanks guys. I would buy the size I need but can't find one. I lied a little...the material I want is Tungsten / Tungsten carbide which seems to get produced in batches of a given size. I've found 1.8" and 2.175" but no 1.875" or 1.9". I could buy a 2.175" and turn in down....if there was a way to turn it down. The sphere doesn't need to be 'perfect' but it needs to be a ball when done, not a blob.

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    Quote Originally Posted by Dumpster_diving View Post
    My recollection is that there's a scientist who created the smoothest spherical surface in the world. Basically by polishing and re-polishing an existing sphere on an apparatus that was simply a precision ring imbedded with lapping compound.

    Would take forever, but theoretically possible at little cost (except for time).
    World's Roundest Object! - YouTube Don't drop it...

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    Quote Originally Posted by GregSY View Post
    Thanks guys. I would buy the size I need but can't find one. I lied a little...the material I want is Tungsten / Tungsten carbide which seems to get produced in batches of a given size. I've found 1.8" and 2.175" but no 1.875" or 1.9". I could buy a 2.175" and turn in down....if there was a way to turn it down. The sphere doesn't need to be 'perfect' but it needs to be a ball when done, not a blob.
    You could try a nicer version of this machine: Stone sphere machine #2 - YouTube
    Some diamond plated cups and a lot of patience would do it...

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    Mythbusters Polishing a Turd - YouTube

    mythbusters delved into this also

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    Quote Originally Posted by GregSY View Post
    .....the material I want is Tungsten / Tungsten carbide .....
    Simple answer .... NO. But it also depends on your quantity needs. If you need a couple then it's still NO. If you need a 1000 then have the manufacturer make them for you.

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    Quote Originally Posted by Milland View Post
    You could try a nicer version of this machine: Stone sphere machine #2 - YouTube
    Some diamond plated cups and a lot of patience would do it...
    And here's a big puppy made with the same process (I think, it's not explicitly stated how it was made): 59, Pound Granite Ball Floating - Grand Kugel -- REAL United States Episode 198 - YouTube

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    Well, after some back and forth. I have a reputable company that will make a tungsten ball for me so it's on order...will take a month until it gets produced.

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    Cool, let us know the cost, I'm curious what it comes to.

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    The only thing I can think of is how they polish bowling balls. Obviously very different material but same outcome.

    Sent from my 2PS64 using Tapatalk

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    My understanding is that ball bearing balls are made by grinding between two vibrating plates at a slight angle they get smaller as they go down to the narrow end. The taper is very slight and careful measuring is all that separates the top quality ones from the not as good kind.
    Bill D

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    Are you sure you're getting the material you want? Tungsten is a dense metal which is reasonably machinable. Tungsten carbide is more like a ceramic. It's what cutting tools are made of. They are very different materials.

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    Well, nothing stops you from ordering 1000 and tossing 999 in the trash. Or find a back shelf and keep them for the next time you need one that size.

    As for reducing a TC ball by 0.05" on all sides, keeping it spherical; that is a job that I would not want. Perhaps you could tumble them in a diamond paste? Even that is going to be expensive, probably more expensive than just paying for the special size.



    Quote Originally Posted by Wild West View Post
    Simple answer .... NO. But it also depends on your quantity needs. If you need a couple then it's still NO. If you need a 1000 then have the manufacturer make them for you.

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    A ball from any machinable material is not a big deal, as long as machining produces a suitable level of precision.

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    I could toss 999 away but at over $200 each that would be spendy.

    It is 90+% tungsten with 'a little' other stuff mixed in....he told me but I forgot exactly. I think copper and a few other more common metals. That's because 'pure' tungsten is very expensive and, I assume, less desirable to work with. In any case, the key attribute I am after - weight - stays decently high. The ball will weigh over 2 lbs. which is about 2X that of stainless steel.

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    Quote Originally Posted by GregSY View Post
    I could toss 999 away but at over $200 each that would be spendy.

    It is 90+% tungsten with 'a little' other stuff mixed in....he told me but I forgot exactly. I think copper and a few other more common metals. That's because 'pure' tungsten is very expensive and, I assume, less desirable to work with. In any case, the key attribute I am after - weight - stays decently high. The ball will weigh over 2 lbs. which is about 2X that of stainless steel.
    Sounds like a tungsten nickel copper alloy, perhaps from these guys: NAECOMET Tungsten Heavy Metals Typical Properties Could have iron too.

    I used TNI materials ages ago for making spark plug ground electrodes for custom plugs. Good spark erosion properties from the tungsten for longer life. And yes, these are very different from the tungsten carbide used in cutting tools.


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