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Thread: CBN insert boring?

  1. #1
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    CBN insert boring?

    Can someone point me to a CBN boring bar setup suitable for .400 bores? I've never found a source for CBN inserts ground with suitable clearance for small bores..... does such a thing exist?

  2. #2
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    Could you do solid carbide boring bars?

  3. #3
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    Quote Originally Posted by Butch Lambert View Post
    Could you do solid carbide boring bars?
    I've tried these to no avail

  4. #4
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    i bought some insert boring bars in amazon
    one does 473 based cases barely
    you will have to search..i got no data

  5. #5
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    Quote Originally Posted by alinwa View Post
    I've tried these to no avail
    How are solid carbide bars failing you? (I don't know of any CBN inserts that small, but am trying to understand the problem.)

    GsT

  6. #6
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    my guess is they flex.
    i use a couple and always do multiple cuts at the same depth to get
    the desired number
    Quote Originally Posted by GeneT View Post
    How are solid carbide bars failing you? (I don't know of any CBN inserts that small, but am trying to understand the problem.)

    GsT

  7. #7
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    Quote Originally Posted by GeneT View Post
    How are solid carbide bars failing you? (I don't know of any CBN inserts that small, but am trying to understand the problem.)

    GsT
    Somewhere around RC36-40 carbide just seems to give up the ghost, in certain steels. For example, the drops a fellow sent me are marked RC37-ish, one set is 416 the other is 17-4

    I'll have to go down and check but if memory serves the 416 cut and the 17-4 just screeched

    This ties in with another post concerning opening sizer dies. I have some carbide insert tooling that cuts Redding dies leaving a glassy-smooth finish. But the case is thin enough that I've cut thru it.

    I have many other dies to try cutting and so far nothing carbide has done the trick. I have tried some solid ground carbide as well as affixing a carbide 3/8 endmill sideways

    I've always heard of "ceramic" and "boron" as being suitable for stuff harder thn RC40-50 but all the tooling I've seen make it look as though the product is "sintered" or somesuch and needs a lot of bottom support and near vertical support below the cutting edge. ie "overhang" must be minimal to account for low tensile strength.

    I've pretty much stopped modifying dies because of this, preferring to just whack out an interim die to use un-hardened while waiting the (year or more??) for a die to be made. It's a pain right now because I've developed 4 different chamberings in the last 6mo as I'm recording youtube vids.....kinda' documenting the "wildcatting" process. I'd like to videotape exactly how I bore out my dies but at this point my success rate is about two dies forward and one die back

    In other words I've screwed up as many as I've succeeded with. You give me a 300WSM Redding die and I'll modify it perfectly 9/10 of the time but run it in to a 300 RUM depth and things get wikky-wakk

    Give me a Forster die, or RCBS and I'll call in every banshee for 6-8 miles

    Little 6BR stuff? PPC? I'm OK but not great....depth easy but now diameter becomes a problem

  8. #8
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    well, foo!

    Quote Originally Posted by alinwa View Post
    Somewhere around RC36-40 carbide just seems to give up the ghost, in certain steels. For example, the drops a fellow sent me are marked RC37-ish, one set is 416 the other is 17-4

    I'll have to go down and check but if memory serves the 416 cut and the 17-4 just screeched

    This ties in with another post concerning opening sizer dies. I have some carbide insert tooling that cuts Redding dies leaving a glassy-smooth finish. But the case is thin enough that I've cut thru it.

    I have many other dies to try cutting and so far nothing carbide has done the trick. I have tried some solid ground carbide as well as affixing a carbide 3/8 endmill sideways

    I've always heard of "ceramic" and "boron" as being suitable for stuff harder thn RC40-50 but all the tooling I've seen make it look as though the product is "sintered" or somesuch and needs a lot of bottom support and near vertical support below the cutting edge. ie "overhang" must be minimal to account for low tensile strength.

    I've pretty much stopped modifying dies because of this, preferring to just whack out an interim die to use un-hardened while waiting the (year or more??) for a die to be made. It's a pain right now because I've developed 4 different chamberings in the last 6mo as I'm recording youtube vids.....kinda' documenting the "wildcatting" process. I'd like to videotape exactly how I bore out my dies but at this point my success rate is about two dies forward and one die back

    In other words I've screwed up as many as I've succeeded with. You give me a 300WSM Redding die and I'll modify it perfectly 9/10 of the time but run it in to a 300 RUM depth and things get wikky-wakk

    Give me a Forster die, or RCBS and I'll call in every banshee for 6-8 miles

    Little 6BR stuff? PPC? I'm OK but not great....depth easy but now diameter becomes a problem
    Well, I've never tried to do what you're doing, and you may have already tried them, but Sandvik makes some super-rigid solid-carbide boring tools. I have part number CXS-06T098-20-6220R 1025. These have a wedge-shaped back end that is made to mate with a special holder, to ensure 'correct' orientation. I don't have the p/n for the holder, but I've used an ER-16 collet instead and never had an issue getting a good cut. Anyhoo, if you haven't tried them, take a look - they might be worth a shot.

    GsT

  9. #9
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    Quote Originally Posted by rsmithsr View Post
    my guess is they flex.
    i use a couple and always do multiple cuts at the same depth to get
    the desired number
    Solid carbide flex? What do you use in place of it?

  10. #10
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    Boring Bar

    Have been using this boring with good results taking lite cut with my Heavy 10.

    Chet


    Click image for larger version. 

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  11. #11
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    you need to go look at some small hole solid carbide and see just how small the bar section can be.

    Quote Originally Posted by Butch Lambert View Post
    Solid carbide flex? What do you use in place of it?

  12. #12
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    I do have solid boring bars all the way from .090 to .490 both larger and smaller
    and use a lot. The insert bar is only used when I need to bore a little deeper and it does a good job of doing it.

    Chet


    Click image for larger version. 

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    Last edited by coyotechet; 12-27-2021 at 11:57 PM.

  13. #13
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    Quote Originally Posted by rsmithsr View Post
    you need to go look at some small hole solid carbide and see just how small the bar section can be.

    Mr Smith Sr. It appears that you have done little machining.

  14. #14
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    Notched carbide

    McMaster Carr Notched carbide Ultrahard cheap

  15. #15
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    Quote Originally Posted by CharlieH View Post
    McMaster Carr Notched carbide Ultrahard cheap
    Thanks Charlie I'll order some

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