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Re: Tapping in Mill?

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  • ballendo
    Steve, Are you using a dual-cone friction type tapping head for the cases you re referring to? Because that s what I m referring to. Otherwuise it s apples and
    Message 1 of 18 , Apr 30, 2007
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      Steve,

      Are you using a dual-cone friction type tapping head for the cases
      you're referring to? Because that's what I'm referring to.
      Otherwuise it's apples and oranges and we agree.

      I only added the "careful with steppers" note because although many
      folks use tapmatic types; there's a LOT of folks here. Some who may
      not realise that the innerds of that type (which will easily work as
      you've described) don't mnatch the innerds of the Procunier type.
      (which will be problematic, IMO/E)

      The issue with a dualcone friction clutch type is that it requires
      syncronisation not unlike rigid tapping. This is easy when
      the "human feedback device" is present. Much less so when you have
      to basically match the lead and keep just enough AHEAD of it to have
      sufficient pressure applied to keep the cones engaged so that the
      tap advances at the proper rate to keep up with your programmed
      rate. If the pressure is too low (for THIS type tapping head), it
      will stop turning and this will mean that your tap is start-stop-ing
      its way through the material. Not a good thing.

      Hope this helps,

      Ballendo

      --- In mach1mach2cnc@yahoogroups.com, Steve Blackmore <steve@...>
      wrote:
      >
      > On Mon, 30 Apr 2007 07:55:39 -0000, you wrote:
      >
      >
      > >Because you'd have to press hard enough to keep it driving, and
      not
      > >stall the stepper. A servo could follow this; but I'd be
      skeptical of
      > >getting reliable results using a stepper (with THIS type).
      > >
      > >A stepper works fine for other types of tapping head not relying
      on
      > >specific pressure level(s) to engage feed.
      >
      > A stepper is capable of "pressing hard".
      >
      > Is 130Kgs+ good enough? That's what Tony Jeffree got before he
      backed
      > off crushing the bathroom scales <G>.
      >
      > I've snapped a few milling bits too - and I'd consider that far
      more
      > pressure than that required to keep a tapping head driving.
      >
      > Torque does drop off with speed, but as long as you keep within the
      > machines specific capabilities, it works fine. I've tapped M2.5 to
      M12
      > with my stepper driven lathe, my mill has even less of a problem
      as it's
      > driving a 30Kg head down as well.
      >
      > Steve Blackmore
      > --
      >
    • Steve Blackmore
      ... One of mine has a clutch similar to Procunier, it needs little more than a kilo of pressure to engage clutch. Do Procunier need more than 130Kg downforce?
      Message 2 of 18 , May 1, 2007
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        On Tue, 01 May 2007 03:49:45 -0000, you wrote:

        >Are you using a dual-cone friction type tapping head for the cases
        >you're referring to? Because that's what I'm referring to.
        >Otherwuise it's apples and oranges and we agree.

        One of mine has a clutch similar to Procunier, it needs little more than
        a kilo of pressure to engage clutch.

        Do Procunier need more than 130Kg downforce?
        Says nothing in their manuals.

        Steve Blackmore
        --
      • Tony Jeffree
        ... Sounds excessive to me.... Regards, Tony
        Message 3 of 18 , May 1, 2007
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          At 08:24 01/05/2007, you wrote:
          > >Are you using a dual-cone friction type tapping head for the cases
          > >you're referring to? Because that's what I'm referring to.
          > >Otherwuise it's apples and oranges and we agree.
          >
          >One of mine has a clutch similar to Procunier, it needs little more than
          >a kilo of pressure to engage clutch.
          >
          >Do Procunier need more than 130Kg downforce?
          >Says nothing in their manuals.

          Sounds excessive to me....

          Regards,
          Tony
        • ballendo
          Steve, I ll try to clarify this one last time... It s not the total force that s the issue. It s the fact that this type has an ANALOG clutch. Sounds like what
          Message 4 of 18 , May 1, 2007
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            Steve,

            I'll try to clarify this one last time...

            It's not the total force that's the issue. It's the fact that this
            type has an ANALOG clutch. Sounds like what you have is a "digital"
            clutch. Either on or off. Tapmatics and their clones are of this
            type. Their engangement is over a range of distance; but the
            engagement itself is fully on or fully off. That's why these types
            have a torque release which the wedge clutch types do not...

            The ANALOG clutch in the procunier is anywhere from completely off
            to completely on(AND everything in-between; it's analog) depending
            upon feed pressure. So as long as the feed pressure exactly keeps
            up with the feed of the tap through the material, the clutch stays
            fully engaged and everything works as expected.

            If you are using a DP, an operator providing a steady pressure
            downwards will effect this and you'll not have any problems. For the
            sake of explanation: The operator could be replaced by a bucket of
            lead of an appropriate weight, applied to turn the DP downfeed. (If
            the weight were too much, you'd bugger the threads.)

            Now try the same with a stepper. The stepper will either be pressing
            too hard or too lightly; it is non-adaptive to the feedrate needed
            to keep the clutch fully engaged. If you're putting 130Kg into it,
            you'll likely bugger the threads. And...

            The feedrate has to match the feed of the tap through the material
            with this type of tapping head. If not, the tap will start and stop
            repeatedly. Bad.

            I mentioned that servos could work because you could feed them ahead
            of the proper rate and then following error would effect the same
            result as the human operator. (It'd increase and decrease to smooth
            out the clutch feed. In effect it's providing a "filter" of the
            digital into the analog required.

            Anyways, enough bandwidth on this, eh? Folks can decide for
            themselves, and the Tapmatics work. As do the simpler tension-
            compression holders seen in screw machines and turret lathes. (You
            can get a procunier to work too; but it will far more problematic
            than the other types, IMO/E.)

            Ballendo





            --- In mach1mach2cnc@yahoogroups.com, Steve Blackmore <steve@...>
            wrote:
            >
            > On Tue, 01 May 2007 03:49:45 -0000, you wrote:
            >
            > >Are you using a dual-cone friction type tapping head for the
            cases
            > >you're referring to? Because that's what I'm referring to.
            > >Otherwuise it's apples and oranges and we agree.
            >
            > One of mine has a clutch similar to Procunier, it needs little
            more than
            > a kilo of pressure to engage clutch.
            >
            > Do Procunier need more than 130Kg downforce?
            > Says nothing in their manuals.
            >
            > Steve Blackmore
            > --
            >
          • Vince Endter
            In this video: http://www.flyingcritters.com/video/Tap.wmv I am tapping with a Procunier 3E tapping head and a 1/2 tap. I programmed the down feed at 95% of
            Message 5 of 18 , May 1, 2007
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              In this video:
              http://www.flyingcritters.com/video/Tap.wmv
              I am tapping with a Procunier 3E tapping head and a 1/2" tap. I
              programmed the down feed at 95% of the calculated feed rate. The
              upfeed was at 190% of the calculated feed rate. I drilled and tapped
              100+ holes in the plate. The tap did not start and stop rotation. It
              all went very smooth and faster than rigid tapping because the spindle
              never changed direction.

              Vince
            • Steve Blackmore
              ... With a stepper ?? ;) Steve Blackmore --
              Message 6 of 18 , May 1, 2007
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                On Tue, 01 May 2007 12:12:29 -0000, you wrote:

                >In this video:
                >http://www.flyingcritters.com/video/Tap.wmv
                >I am tapping with a Procunier 3E tapping head and a 1/2" tap.

                With a stepper ?? ;)

                Steve Blackmore
                --
              • Vince Endter
                No, servo. Vince
                Message 7 of 18 , May 1, 2007
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                  No, servo.

                  Vince

                  > With a stepper ?? ;)
                  >
                  > Steve Blackmore
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