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Thread: Radius on TC Cutting Edge?

  1. #1
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    Default Radius on TC Cutting Edge?

    I have tried to get an answer to this in my thread about a face milling cutter, but it seems to be ignored or lost there. So, here goes in a separate thread of it's own.

    When sharpening a TC lathe style tool, is it desirable to have a small radius on the cutting edge or should it be as sharp as the technique and abrasives will allow?

    I ask this because I like to sharpen HSS as sharp as possible but have seen commercially sharpened TC both razor sharp and with a small (0.001" - 0.002") radius. Which is best? Why?
    Paul A.

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  2. #2

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    My understanding is that carbide cutters are usually supplied with a minute radius on the edge to reduce chipping and make them last longer on tougher materials like steel. HSS is not as hard but also doesn't chip as easily so can be used with a dead sharp corner. There may be carbide inserts supplied with sharper edges intended for softer materials such as aluminum.
    .
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  3. #3
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    Sharpening TC lathe tooling went out of date at least 30 years ago, replaceable tip tooling enjoys far more advanced profiles, grades and coatings.

  4. #4
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    Quote Originally Posted by old mart View Post
    Sharpening TC lathe tooling went out of date at least 30 years ago, replaceable tip tooling enjoys far more advanced profiles, grades and coatings.
    Amen to that. Brazed carbide and HSS tooling are pretty much obsolete in today's world...
    Keith
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  5. #5
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    Small radius is better than uber-sharp for both TC and HSS if you take heavy cuts. Making one is tricky at best, try diamond lapping compound and soft polishing wheel if you must.

  6. #6
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    I like mine as sharp as possible. Also, on a fly cutter or face mill, it's better to have an angle on the leading edge than straight vertical. It can be anywhere from 5 to 45 degrees, depending on the variables.

  7. #7
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    Quote Originally Posted by old mart View Post
    Sharpening TC lathe tooling went out of date at least 30 years ago, replaceable tip tooling enjoys far more advanced profiles, grades and coatings.

    Quote Originally Posted by LKeithR View Post
    Amen to that. Brazed carbide and HSS tooling are pretty much obsolete in today's world...

    In the home shop I respectfully disagree.

    Stefan Gotteswinter has an interesting video on the subject:




    https://www.youtube.com/watch?v=UUVvgcvlbBs

  8. #8
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    Is it worth it when the Chinese sell the things for 1 each, and WNMG's and TNMG's have 6 edges and are available sharp for aluminium which are good for finish cuts on steel as well.

  9. #9
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    We did sort of loose our focus in that thread....

    All else being equal it's likely a good idea in this case due both to the interrupted cuts and since a radius promotes a better surface finish by cutting a shallow rounded form instead of a sharp pointed one.

    If it were me doing what you're doing I'd go for something like a .01 to .015 radius. So shoot for a touch under a 1/32" diameter since the eye tends to see diameters easier than radii.

  10. #10
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    A micro radius used to put on some tools so coatings would adhere, they apparently wouldn't stick to a sharp corner.

    I leave a sharp corner.

    There are still lots of face mills and wheel cutters made of HSS that need to be sharpened. Annular cutters also. I have a brazed carbide tipped face mill I use for nasty and rusty material that's not worth the risk to six inserts.

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