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Thread: Best inserts for finishing gummy 1018?

  1. #11
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    I don't really see anything in that pic to be too proud of. Insert looks dull and the shiny surface with a bur on the end is not a clean cut.

    I'll contribute a bit.
    Last couple days I've been turning 1018 bar stock. From 1.5"-2.25" in diameter 9xx rpm with tpg 321, 322, 323, carbide inserts. I was making multiple parts and needed to hit the size within a couple thou. I'd need to run out to the shop to check what the feed and grade inserts are.

    ETA...
    910 rpm, .0042 per rev, doc range .050-.002, insert grade I55
    Last edited by Boostinjdm; 01-21-2017 at 10:48 PM.

  2. #12
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    Quote Originally Posted by Boostinjdm View Post
    I don't really see anything in that pic to be too proud of. Insert looks dull and the shiny surface with a bur on the end is not a clean cut.

    I'll contribute a bit.
    Last couple days I've been turning 1018 bar stock. From 1.5"-2.25" in diameter 9xx rpm with tpg 321, 322, 323, carbide inserts. I was making multiple parts and needed to hit the size within a couple thou. I'd need to run out to the shop to check what the feed and grade inserts are.
    Damn, I'll need a better microscope if others can see dull insert on a crappy cell phone pic

    A couple of thou tolerance in 1018 is not more difficult than dozens of thou. Less than 0,01mm or 4 tenths gets tricky with less than 100% success rate on a old worn out clunker.

  3. #13
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    I think it looks fine. The burr on the end is easily fixed with a file.

  4. #14
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    You're the one that said, "It's the best thing since sliced bread on crappy steel." Your pic does not support that. That's all.
    I not saying that TPG inserts are the best thing either, but they're cheap, work on lots of materials, and are very flexible as far as holder options.

    To put some perspective on my previous post, I consider most people that claim to work to tenths FOS. Especially hobbyists and self proclaimed, but untrained machinists. I am most definitely not a machinist. I'm a welder/fab/repair guy. I machine a lot of stuff as a means to an end when repairing or building something.
    Last edited by Boostinjdm; 01-21-2017 at 09:33 PM.

  5. #15
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    Quote Originally Posted by Boostinjdm View Post
    You're the one that said, "It's the best thing since sliced bread on crappy steel." Your pic does not support that. That's all.
    I not saying that TPG inserts are the best thing either, but they're cheap, work on lots of materials, and are very flexible as far as holder options.

    To put some perspective on my previous post, I consider most people that claim to work to tenths FOS. Especially hobbyists and self proclaimed, but untrained machinists. I am most definitely not a machinist. I'm a welder/fab/repair guy. I machine a lot of stuff as a means to an end when repairing or building something.
    I think we really need to see the mirror finish you get on with your TPG inserts.

    Getting a picture of the shiny surface finish proved to be a tricky but here is another:
    About halfway there is a 0,035mm or 0,0014" step after I tested 7 tenth cut of depth. Even less than 7 tenths DOC seemed to work, reasonably well for dull insert

    IMO more remarkable is that this was done AFTER turning hardened >HRC60 bearing race with the same "dull insert".
    Last edited by MattiJ; 01-21-2017 at 10:11 PM.

  6. #16
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    Means much more with some details as to what sort of machine it was done on.

    AFAIK the ceramic inserts are deliberately "not sharp", and the shiny finish comes from the burnishing action as the material is "pushed off" the surface, and not really "cut". But that takes power and rigidity not found with the machines that most here use. You presumably are using such a machine if you were hard turning a bearing race.

    I don't think "cutting" ever really gives that polish, there has to be a "rubbing" element to the "cut".

    But to be perfectly frank, what I see is a high polish on what is a somewhat irregular cut, based on the reflections in the picture shown in post 15. The polish may be causing the reflections to be more distinct, however, I cannot judge the absolute size of the irregularities from the reflection, and they may be small.
    1601

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  7. #17
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    Quote Originally Posted by J Tiers View Post
    Means much more with some details as to what sort of machine it was done on.

    AFAIK the ceramic inserts are deliberately "not sharp", and the shiny finish comes from the burnishing action as the material is "pushed off" the surface, and not really "cut". But that takes power and rigidity not found with the machines that most here use. You presumably are using such a machine if you were hard turning a bearing race.

    I don't think "cutting" ever really gives that polish, there has to be a "rubbing" element to the "cut".

    But to be perfectly frank, what I see is a high polish on what is a somewhat irregular cut, based on the reflections in the picture shown in post 15. The polish may be causing the reflections to be more distinct, however, I cannot judge the absolute size of the irregularities from the reflection, and they may be small.
    Yes, part of fancy shine is probably partly from burnishing action. But the insert edge is also reasonably sharp, otherwise I don't see how its possible to take a 7 tenths or even less DOC with still making tiny chips.

    I cant make any quantitative claims on the surface roughness but shiny surface really shows the imperfections in the reflections.
    If you look at suitable angle you can also see some cyclic marks (like tiny chatter marks) that probably comes from harmonics of headstock gears or spindle bearings. And part of variation is because I was feeding manually to avoid feed gear resonances. Using automatic feed the surface finish is really showing up all kind of patterns. (old and worn lathe)

  8. #18
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    I want to find out about using hard stuff in a shear capacity. After watching several youtube videos on "shear" some call tangental shear , finishing 1018 on light lathes , I thied it and was amazed at the results. All the guys doing it used HSS i think , so far for me HSS , even the best stuff i have doesnt last very long .

    Thanks
    Dave Lawrence

  9. #19
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    There nothing wrong with a burnishing action it cut happens first. I have "wiper action" WNMG carbide that does the same thing, by design. Cut first, "wipe" after. What I can't do though is take 7/10ths DOC so if I mess up my final 3-5 thou final pass and don't hit the number, I have to resort to "other methods". As I'm often too lazy to then mount HSS tooling, I reach for the sandpaper

  10. #20
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    Quote Originally Posted by lalatheman View Post
    I want to find out about using hard stuff in a shear capacity. After watching several youtube videos on "shear" some call tangental shear , finishing 1018 on light lathes , I thied it and was amazed at the results. All the guys doing it used HSS i think , so far for me HSS , even the best stuff i have doesnt last very long .

    Thanks
    Dave Lawrence
    I have tried HSS shear tool and agree that it dulls quite fast. Have also tried carbide insert repositioned as a shear tool, seemed to last longer than HSS shear tool but I get similar surface roughness with the DCGT insert used in normal way anyways so no biggie.

    With small DOC and insufficient surface speed my experience is that HSS shear tool and sharp DCGT insert produce quite similar surface finish. I'd vote for good DCGT carbide because I get more consistent results and it lasts way longer.
    Surface finish with sharpened KY1615 ceramic LOOKS better but I doubt there is much difference in actual surface roughness values, not at least on "ordinary" lathe. On a 10EE or a nice Schaublin maybe...

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