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  • #46
    Originally posted by Norman Atkinson
    We've been through all this before and before.

    The classic answer is to use a rear tool post and run the lathe forwards but using a tool inverted at a 7 degree slope. Set at exact tool height, of course.

    The top of tool remains straight but has a convex grind along it. The recommended grind is a vee of 140 dgrees but I found a simple curved female grind( calm down, fellas) was enough. The front of the tool had a male 140 degree vee'd edge.

    Norman
    Norman, let me see if I understand you description.

    7 degree slope mens that the bottom surface of the inverted toll present a positive 7 degrees rake, right?

    The word convex and female puzzle me. W are still talking about the bottom surface of the tool. Convex, to me, means that the V looks like a house roof not a V groove. Female, means (i think) hollow in the center, in this case a groove or a arched though ground lenghtwise. Right?

    As for the tool front I understand a male V to resemble the stern of a ship.

    Please clarify thanks

    Mauro
    In Austin TX
    Mauro Gaetano
    In Austin TX

    munged email
    capialized need be replaced with symbols
    mauroUNDERSCOREgaetanoATearthlinkDOTnet

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    • #47
      Part off Blades

      I would agree that it is difficult to comprehend. Bit like being avalanched and having to spit!

      OK- lets do the blade itself.
      Along the top of the blade( about an inch) is a female vee of 140 degrees or a curve( from a worn slitting wheel) Female is female- going into as in a con-cave.
      The front of the tool has a male chamfer of 140 degrees- male to go out and into over or when one is vexed- you go out. ( Sounds a bit but that's the way of the World)

      The tool is inclined at 7 degrees to the work( at centre height)
      If you think- you don't need to put a back rake on the tool because it is inclined. So all that a re-grind needs is a tiny bit of grinding off at the front.
      Actually, it is simply a normal cutting tool. You could use a flat topped lathe tool in the rear tool post- instead of grinding back rake.

      I hope that that is clearer.

      Why not E-mail me at [email protected]
      In truth, it is easier to draw than write about.

      Comment


      • #48
        Thanks Norman, much clear now.
        Exaggerating the idea, the tool act as a scoop.
        I am using now a T blade on a home made rear post with no agle because it has no height adjustment to compensate for different protrusions.

        Even witgh a simple flat tip, zero rake, it works well on my Chinese 9x20 but I am always open to improvement particularly if this is a old technique validated by time.

        Agree, drawing is the language of geometry, words are a poor tool for shapes.

        Mauro
        In Austin TX
        Mauro Gaetano
        In Austin TX

        munged email
        capialized need be replaced with symbols
        mauroUNDERSCOREgaetanoATearthlinkDOTnet

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        • #49
          Weeeeeeeeeeeeeell that clears that up..... But seriously- it seems like the HSS and carbides have their respective advantages and disadvantages. Plenty of reasons to have both.
          I'll be back with many more questions.

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          • #50
            Originally posted by Bill Pace
            I chose the one already mentioned, from ENCO, the Newcomer. With getting the kit, you'll get everything ready to use with your new QCTP including 10 of the inserts. Get one that takes the narrow inserts, it is much easier on your lathe -- in the Newcomer its .087. Heres the one I chose ---
            http://www.use-enco.com/CGI/INSRIT?PMAKA=422-2914

            As mentioned, its qualifies for free frt, too --- use code PRPT12 (that'll expire end of the month...)
            Going back in time a few days.....
            Bill,
            What's the max reach with that setup?
            Thanks
            Dave P.

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            • #51
              Click that enco link, the resulting page will have a link to Master Catalog page 188, blade cutting depths are on a chart at the bottom of that page.

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              • #52
                I think I'm dangerously over my "Piss off Norm" limit this week , but I have to agree with BadDog, Peter et al: I have the Sandvik parting tool system, and it's fantastic. I think the reason it works so well is because the nose is shaped like a chute that flares outwards: it curls the chip away and up from the workpiece, minimizing the cutting forces.

                Like Norm describes, Geo Thomas shows some fancy cutting tip geometries to minimize parting forces, but there's no way a home-shop guy could make the curved 3D nose shape on the Sandvik, Newcomer, et al parting tips.

                Now, along those same lines, Sandvik also has a very cool slitting/slotting saw that uses the same inserts: basically picture 8 of the parting inserts mounted radially on a milling arbor. I just got this in last weekend, and I've been cleaning the Excello since, but I'm dying to try this on some 4140 Pre Hard:

                "Twenty years from now you will be more disappointed by the things that you didn't do than by the ones you did."

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                • #53
                  Lazlo,

                  As well as those carbide parting tools work, that blade you have there with the 8 inserts, ought to be one badass metal moving monster!!!!

                  Chris

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                  • #54
                    I have been following this carfully. I need a cutoff tool (Ihave been using a home ground HSS 1/2 tool bit.) My lathe came with a Aloris holder AXA7 that is designed for T shaped cut off blades. I am going to start with that, knowing that some day I will want to move up to a carbide system. My question,

                    What assortment of widths do I get? I can go from .040 to 1/8 I am liiking at the Enco USA blades.

                    I will be cutting cast iron and steel up to 2 in thick

                    Thanks

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