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  1. #1
    Join Date
    Dec 2011
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    Default Kyocera Inserts Chipping

    I work in the Manual Arts Department of a High School. Unfortunately, the younger teachers do not have a trade background and their sharpening and lathe skill are not as honed.
    A current project involved the students turning down a M16 hex coupler that is 50mm long. The lathe tool holder has Kyocera inserts that are constantly chipping and fracturing.
    It is this unit they are using from Hare & Forbes. The inserts are General Purpose.

    https://www.machineryhouse.com.au/L044


    Have you got any solutions or tips that you might like to offer?

    Is there a high quality insert available for this tool holder? I am not sure if the school can outlay for diamond tipped inserts.

  2. #2
    Join Date
    Apr 2012
    Location
    Healesville
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    1,160

    Default

    I have had that problem before.
    Ensure that there is no debris between the bottom of the tool post and the top slide and do the same with the bottom of the top slide to th saddle, swarf/debris can cause the tool post to rock and the insert digs in.
    If it is clean then check that the tool post is sitting flat on the top slide and the top slide is sitting flat on the carraige, brg blue should give you a good idea of flatness.

    Cheers, shed

  3. #3
    Join Date
    Jul 2016
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    Default

    I agree with shed, this isn't going to be an insert issue, I highly doubt that anything a simple coupler is made of will challenge carbide. You have something in the cross or compound slide that's allowing things to wriggle around.

    Also is the seat under the insert chipped or broken? Check nothing is between the holder and seat or seat and insert.

  4. #4
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    Jun 2011
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    Default

    Quote Originally Posted by Kidbee View Post
    I work in the Manual Arts Department of a High School. Unfortunately, the younger teachers do not have a trade background and their sharpening and lathe skill are not as honed.
    A current project involved the students turning down a M16 hex coupler that is 50mm long. The lathe tool holder has Kyocera inserts that are constantly chipping and fracturing.
    It is this unit they are using from Hare & Forbes. The inserts are General Purpose.

    https://www.machineryhouse.com.au/L044


    Have you got any solutions or tips that you might like to offer?

    Is there a high quality insert available for this tool holder? I am not sure if the school can outlay for diamond tipped inserts.
    It's an interrupted cut, that's hard on carbide. I'd be looking for a tool holder and negative rake tips that are designed to handle the shock loads.

    Or - gasp - use high speed steel and drop the speed down until you get past the interrupted cut then switch back to carbide.

    Oh and FWIW I *loathe* triangular inserts in general and that tool holder looks like crap to me. Cheap crap.

    PDW

  5. #5
    Join Date
    Dec 2011
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    Buderim qld
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    Default

    Quote Originally Posted by PDW View Post
    It's an interrupted cut, that's hard on carbide. I'd be looking for a tool holder and negative rake tips that are designed to handle the shock loads.

    Or - gasp - use high speed steel and drop the speed down until you get past the interrupted cut then switch back to carbide.

    Oh and FWIW I *loathe* triangular inserts in general and that tool holder looks like crap to me. Cheap crap.

    PDW
    PDW, yes it is an interrupted cut and I see that Kyocera make inserts for that. The ones they are using are CA525 but they have a CA535 for interrupted cuts. See screen shot. I do believe the tool holder is a cheaper one. In what way would a better quality one make a difference and what brand would you suggest?
    Attached Images Attached Images

  6. #6
    Join Date
    Jul 2016
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    Melbourne
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    Default

    It might not be the finest available but the geometry of those triangular inserts is simple, im sure the holder is fine. Switching to something negative rake would probably help, but most of all is the tool on center height? that can make a big difference for surviveability,

  7. #7
    Join Date
    May 2019
    Location
    Tucson, Arizona, USA
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    Default

    I agree - make sure the tool is cutting on center (or slightly below) and that the tool holder/post is tight. I use Kennametal cnmg432 inserts on my 16" conventional lathe and they work fine with no chipping issues.
    David

    Desert Hybrids Precision

  8. #8
    Join Date
    Aug 2008
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    near Rockhampton
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    Default

    I would probably be using WNMG inserts, or SNMG of a grade suited for interrupted cut.
    Gold, the colour of choice for the discerning person.

  9. #9
    Join Date
    Mar 2014
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    South of Adelaide
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    What Rpm, feed and depth of cut are you using?
    Using the correct grade will help significant, the first couple of cuts on the corners of the hex are heavy interrupted cuts and P20 inserts struggle to cope with that.

  10. #10
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    Just going by the size of material and the fact if the tool holder linked is being used is there any reason as to why you can't cut under the Hex in one pass?

  11. #11
    Join Date
    Dec 2011
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    Buderim qld
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    Quote Originally Posted by pipeclay View Post
    Just going by the size of material and the fact if the tool holder linked is being used is there any reason as to why you can't cut under the Hex in one pass?
    I will look into that and see how they are approaching the material.

  12. #12
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    Dec 2011
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    Buderim qld
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    Quote Originally Posted by snapatap View Post
    What Rpm, feed and depth of cut are you using?
    Using the correct grade will help significant, the first couple of cuts on the corners of the hex are heavy interrupted cuts and P20 inserts struggle to cope with that.
    Need to find out what spindle speed. Not back to work until Monday. My involvement is that they could not get the insert off after it got chipped and they stripped the Allen key slot in the top pin screw. The inserts are getting chipped often. The students are first time lathe users.

  13. #13
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    Mar 2014
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    South of Adelaide
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    Quote Originally Posted by Kidbee View Post
    Need to find out what spindle speed. Not back to work until Monday. My involvement is that they could not get the insert off after it got chipped and they stripped the Allen key slot in the top pin screw. The inserts are getting chipped often. The students are first time lathe users.
    Sounds like they are over tightening the clamp. It only needs to be nipped up, the clamp only needs to stop the insert lifting.

  14. #14
    Join Date
    Oct 2008
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    N.W.Tasmania
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    Default

    Plenty of good advice has been given here, I think that HSS would be best here, but it would need someone who knew how to grind the tool, whereas your indexable carbide does not. I have never even seen diamond lathe tooling, but I would think that it would be of no advantage to your students, and being harder than carbide, would be much more prone to chipping again. HSS is softer than carbide, but much more resistant to chipping, especially with interrupted cuts, and definitely something you should consider, and if you looked at the Australian '' Eccentric Engineering's " Tangential cutting tool holders, you would have tooling that would do most of the jobs the students have to do, and the included sharpening jig would make the minimal tool touching up easy to perform.

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