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Best inserts for finishing gummy 1018?

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  • #16
    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.
    CNC machines only go through the motions

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    • #17
      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)
      Location: Helsinki, Finland, Europe

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      • #18
        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

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        • #19
          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

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          • #20
            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...
            Location: Helsinki, Finland, Europe

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            • #21
              For those wanting a HSS type cutting tool that holds an edge longer, try Tantung. One note of caution, when grinding, don't quench at all, only air cool. This is one of the things they used before carbide was widely available.
              Kansas City area

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              • #22
                Originally posted by Toolguy View Post
                For those wanting a HSS type cutting tool that holds an edge longer, try Tantung. One note of caution, when grinding, don't quench at all, only air cool. This is one of the things they used before carbide was widely available.
                Never heard of this stuff before but based on the description I found seems promising. Does it require special grinding wheels to sharpen?

                Tantung Description

                Can be used on machines where speeds and rigidity are limited. With tantung tools, older machines can handle increased production loads and help reduce costs. Performs interrupted cuts significantly better than carbides.

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                • #23
                  Originally posted by Axkiker View Post
                  Never heard of this stuff before but based on the description I found seems promising. Does it require special grinding wheels to sharpen?

                  Tantung Description

                  Can be used on machines where speeds and rigidity are limited. With tantung tools, older machines can handle increased production loads and help reduce costs. Performs interrupted cuts significantly better than carbides.
                  Afaik can be sharpened just like HSS but just takes more time. And maybe you could also use diamond wheels since it doesn't contain iron like HSS. "Only" problem is very limited availability and high price. I belive in europe these alloys are more commonly referred as "stellite"

                  http://conradhoffman.com/stellite.htm
                  Location: Helsinki, Finland, Europe

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                  • #24
                    Hah........... nice, thank you.

                    I may have some of the notched cutters, so I will be checking with my pocket magnet, you bet...!
                    CNC machines only go through the motions

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                    • #25
                      So I decided to head in to the "you must be full-of-sh*t tenths category" and see what is the minimum DOC I can get.
                      0,001 mm digital dial gauge set to cross slide and afterwards measured with 0,001mm digi-mike:

                      DOC measured with the dial gauge:
                      0,010 mm DOC, actual diameter from 14,717 to 14,700
                      0,005 mm DOC, actual diameter from 14,701 to 14,695 (still cutting actual chips, albeit almost invisible)

                      Looks like there is 0,003 to 0,004 mm error on measured diameter vs. measured DOC. Or abouts one and half "tenths"
                      Or it could be measurement errors piling up.
                      Location: Helsinki, Finland, Europe

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                      • #26
                        Originally posted by MattiJ View Post
                        So I decided to head in to the "you must be full-of-sh*t tenths category" and see what is the minimum DOC I can get.
                        0,001 mm digital dial gauge set to cross slide and afterwards measured with 0,001mm digi-mike:

                        DOC measured with the dial gauge:
                        0,010 mm DOC, actual diameter from 14,717 to 14,700
                        0,005 mm DOC, actual diameter from 14,701 to 14,695 (still cutting actual chips, albeit almost invisible)

                        Looks like there is 0,003 to 0,004 mm error on measured diameter vs. measured DOC. Or abouts one and half "tenths"
                        Or it could be measurement errors piling up.
                        Whatever the actual measurements, you can positively say that it can take less than you need
                        Amount of experience is in direct proportion to the value of broken equipment.

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                        • #27
                          not clear what you were doing. carbide or hss? what geometry? you know, you can get the diameter down without cutting. the tool just burnishes the work.

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                          • #28
                            Originally posted by dian View Post
                            not clear what you were doing. carbide or hss? what geometry? you know, you can get the diameter down without cutting. the tool just burnishes the work.
                            Same Kennametal KY1615 ceramic insert sharpened with 0 degree relief and 7 degree rake angle, both surfaces now lapped close to mirror polish with 600grit +5 + 1 micron diamond lapping compoud.
                            Location: Helsinki, Finland, Europe

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                            • #29
                              I ground a threading tool out of Stellite. Only a 1/4in bit but holy cow it took a long time. I wish I had had a coarser wheel than the 100grit white wheel on my grinder.

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                              • #30
                                Originally posted by MattiJ View Post
                                Same Kennametal KY1615 ceramic insert sharpened with 0 degree relief and 7 degree rake angle, both surfaces now lapped close to mirror polish with 600grit +5 + 1 micron diamond lapping compoud.
                                Did you round or break the edge , where the two highly polished surfaces come together ?

                                Thanks
                                Dave Lawrence

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