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My part-off tool worked perfectly

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  • #16
    Originally posted by Bented View Post

    Not exactly true, a simple parting operation is easily accomplished by cutting the radii before parting using a straight insert tool.

    ...............................................
    That does, however, cause what is theoretically one operation, to take up at least TWO tooling stations. Even with a QCTP, it requires two tooling changes for the operation. (rounding tool to cutoff, and cutoff back to rounding tool.)

    Also, the tool rounds BOTH sides as it cuts off. If the separate rounding tool does not do both sides, then you need THREE tooling changes. If you make a tool to round both sides, you may as well make it do the cutoff as well, since it spans the area required to do both.

    I actually considered that approach. However, I rapidly realized that I could do the work faster, and get better results as far as burrs, if one tool did it all.

    Using the combination tool (something well known to any turret lathe folks) means one operation, NO movement of the carriage, one tooling station used, and NO tooling changes. The tool also has the minimum burr creation. It's not ALL about doing it in one step, it was also about eliminating second ops.

    By runnng in a cutoff tool after the rounding, there is a good chance that the cutoff will raise a burr. And there goes the advantage, as you may need a second op to deburr.

    I don't see the "easily accomplished" as being "easy", nor useful, if it adds tooling changes, second ops, and time to the operation.

    That is the difference in approach between the mindset for manual operations and the mindset for CNC. The CNC can do the multiple changes, and handle the whole task with a de-burr, although it does take more time even there, than one tool for the cutoff and rounding at once would.

    So the CNC folks can be relatively liberal in the adding of tool changes and operations, since they are all handled by the CNC, and possibly in a totally hands-off manner.
    CNC machines only go through the motions

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    • #17
      There is no tool change, plunge the parting tool straight in to the bottom of the radius then radius the corners and finish part off.

      A CNC lathe will interpolate the radii, no need for a form tool.

      A low dollar lathe will do this all day long.
      A simple example of the conversational programming.
      Click image for larger version

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      Last edited by Bented; 04-24-2022, 10:35 PM.

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      • #18
        Originally posted by Bented View Post
        There is no tool change, plunge the parting tool straight in to the bottom of the radius then radius the corners and finish part off.

        A CNC lathe will interpolate the radii, no need for a form tool.
        Yep, easy peasy. No tool change, no special tool.

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        • #19
          Yes, CNC is a different animal. Using the same tool may not give a good surface everywhere, just because a good tool for parting may not be a good tool for doing other things. But it can be done, I suppose.

          You can DO it that way manual as well. But manual, it would mean tool changes in general, in order not to spend a ton of time on each one.

          However, "low dollar" in CNC is still high dollar when the machine you have is manual.

          That's code for "I know damn well that CNC does everything and makes your breakfast as well, but that damn is one that I just do not give". But, The few minutes to get the tool ground just the way I wanted it, saved a lot of time. And I did not need a CNC. Win all around, and I get paid.

          CNC is good, it gives repeatability, and tends to speed up the process in proportion to the number of setups otherwise needed. For something like this, the CNC can go get stuffed.....! Using CNC for simple stuff is like killing spiders with a pile driver.

          I hadn;t seen ol' Bent Ed for a while, but it figures he'd be in here with "the only right way to do the job" (for a shop that has production tools).

          The job got done, and the time to make the tool was paid for several times over in time saved, even more so when considering no second ops. CNC does not guarantee no burrs.
          Last edited by J Tiers; 04-24-2022, 11:18 PM.
          CNC machines only go through the motions

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          • #20
            You folks are funny.

            I see a shaped tool bit and a program for a cnc machine.

            One is manual and one is written. I do both.

            Why did a tool bit grinding help story go to some other place? I liked the education on formed bits. That is what this story is about.. JR

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            • #21
              Manual vs CNC discussions are no different than HSS vs Carbide tooling, or what ever came before HSS vs HSS. CNC in the home shop is simply natural evolution. 20 years from now most of us will have replaced nearly all manual lathes and mills with CNC. The biggest reason for this? People want machine tools made in the USA again, which is VERY possible with CNC.
              Epoxy granite castings formed over a welded steel frame running linear rails removes the need for heavy castings that are the domain of Asia. High quality linear rails from Japan remove major labor costs and reduces the skill required for fit and finish. Also makes rebuilding the machine a bolt in replacement affair. Instead of Acme rods, it's ball screws, instead of handles, it's servos. Mark my words, it'll happen.
              Last edited by RB211; 04-25-2022, 12:55 AM.

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              • #22
                Originally posted by RB211 View Post
                Manual vs CNC discussions are no different than HSS vs Carbide tooling, or what ever came before HSS vs HSS. CNC in the home shop is simply natural evolution. 20 years from now most of us will have replaced nearly all manual lathes and mills with CNC. The biggest reason for this? People want machine tools made in the USA again, which is VERY possible with CNC.
                Epoxy granite castings formed over a welded steel frame running linear rails removes the need for heavy castings that are the domain of Asia. High quality linear rails from Japan remove major labor costs and reduces the skill required for fit and finish. Also makes rebuilding the machine a bolt in replacement affair. Instead of Acme rods, it's ball screws, instead of handles, it's servos. Mark my words, it'll happen.
                Well, that was pretty heavy Son. Took me a second to re-read it. I did. And then I read it again, for clarification. JR

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                • #23
                  Interestingly, I made another similar tool for a thicker part. Similar not in the corner rounding, I did not do that part, but in the angled cutting edge.

                  But, even though the tool gave a quite visibly angled cut, with the tip at the parted off portion clearly ahead, it did NOT reliably part off the part with the "fin" remaining on the stock. About half the time it was attached to the removed portion, and pretty tightly attached, too.I had to tear it off with pliers, and then remove the rest with a countersink. Tool was freshly sharpened, and peeled dust all across if advanced very slowly, so not due to dullness.

                  I still don't know why it was not working right. But I changed the feed-in speed to be slower, and then it would part off correctly. Material was stainless 303, which otherwise behaved very well for machining.
                  CNC machines only go through the motions

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