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Thread: Kyocera Inserts Chipping
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15th May 2019, 09:52 AM #1Intermediate Member
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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.
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15th May 2019, 10:13 AM #2Most Valued Member
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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
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15th May 2019, 10:31 AM #3Most Valued Member
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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.
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15th May 2019, 12:06 PM #4Most Valued Member
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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
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15th May 2019, 01:11 PM #5Intermediate Member
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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?
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15th May 2019, 01:38 PM #6Most Valued Member
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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,
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15th May 2019, 03:54 PM #7Intermediate Member
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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
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15th May 2019, 05:31 PM #8Pink 10EE owner
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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.
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15th May 2019, 06:47 PM #9Diamond Member
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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.
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15th May 2019, 07:31 PM #10Most Valued Member
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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?
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15th May 2019, 09:05 PM #11Intermediate Member
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15th May 2019, 09:15 PM #12Intermediate Member
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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.
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16th May 2019, 07:08 PM #13Diamond Member
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17th May 2019, 09:15 PM #14Diamond Member
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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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