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Scraping question

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  • Scraping question

    Evening all,
    Im in the process of adding one of these: in er16 to a SIP Geneve inspection microscope.
    This involves making a new slide to mate to where the optics used to go.
    The slideway is a flat and v. Ive roughed out an L from cast iron, and can mill the V and the flat to the approx correct shape.
    The original ways are scraped, and the scraping is not worn visibly on either the fixed or the moving part.
    The ways are roughly 10 mm wide, and 100 mm long.
    Firstly what is the correct order to do the v and flat in?
    I assume there will be some cyclic do one, then the other repeat?
    Secondly I intend to use this with micro carbide drills/mills.
    For this I need to ensure the spindle is totally parallel to the ways.
    This probably involves some scraping of the other side of the slide. Any guidance on this?

    Just south of Sudspumpwater UK

  • #2
    Subject to more expert persons than myself correcting....... I'll jump in since nobody else did.... but it isn't clear exactly how it is made.....

    It sounds like your "V and flat" is like a lathe bed..... is that correct? That means that some form of gibbing down is used as with a carriage to hold it down..

    But I would have expected it to be made more like a crosslide way, with a double flat and male dovetail. That is "self holding", with an internal gib to take up the slack, no need for an external hold-down.

    Can you either describe it better, or post a picture? The approach may be rather different for different constructions, and I don't want to go off on a tangent.

    Keep eye on ball.
    Hashim Khan


    • #3
      Photobucket appears to be dead at the moment, but when its back Ill post some pics.
      In the meantime it is indeed sort of like a lathe bed stood on end.
      Looking at the 'fixed' part the V is on the left, there is a slot in the middle, and a flat way on the right.
      Inside the slot a T nut cross section rack resides. This is the up/down control, driven by a pinion in the slot.
      It also forms the securing mechanism for the slideway. It is sprung loaded to a plate that bolts to the slide in between the v and flat ways.
      The V sticks out of the slide portion and into the fixed portion, just like a lathe saddle in reverse.
      There is a camlocking device that pulls the rack towards the slide to clamp the slide at the required place.
      Hopefully that makes sense. Its very obvious in a photo...

      Its back, heres a couple of pics

      The 'fixed portion':

      The slide I have to make a new one of:

      And the roughed out block of CI to start from:

      Last edited by small.planes; 06-20-2012, 05:16 AM.
      Just south of Sudspumpwater UK


      • #4
        With a well set up mill you should be able to "fly-cut" all of the "vee" and "flat" surface with a very fine "over-lapping swirl" pattern typical of a good fly-cut finish.

        A final finish "swipe" with a good oil stone and perhaps a part of a sheet of "wet and dry" cutting paper should finish it off as you want.

        If you prefer a scraped finish the work should be minimal.

        I have two small universal tool and cutter grinders that should do it with a "saucer" normal wheel - just like a fly-cutter. (The columns can be rotated on their base/s on the grinder tables)


        • #5
          You have to get the sides of the V and the flat surface all set up together, because any error of the flat will require the "V" to either move down, or rotate, meaning a full re-scrape of it.

          I think I would make a "model" piece that fits the fixed V, then from that a "gage" for the moving V.

          I would then machine and scrape the moving V to match the gage, machining the flat to be a bit higher than required, and finally scrape the flat to the correct height to match the V.

          The flat is easier to scrape than the V, so it should be easiest to fit to the correct height.

          Once that is set, then the top surface is machined and scraped to parallel as needed.

          Are you sure that holding system is good for a powered spindle as opposed to an optical system that has no forces on it?

          Keep eye on ball.
          Hashim Khan


          • #6
            Thanks, now I have a plan to proceed:
            Machine the V, then scrape it, ensuring the Flat is still hidden in the metal, then uncover the flat to make the slide mate correctly

            This unit is for very small carbide drills. The sort that snap if you look at them wrong.
            That's the reason for the high speed spindle, My TOS only goes to 4500 rpm, which works ok, but you have to be even more careful.
            I have used them by pecking 1 thou at a time against the quill stop but its a pain.

            The column on this microscope is 2" in diameter, and the whole thing is made from large chunks of cast iron, its way more sturdy than my Proxxon Mini mill (MF-70), so I think it'll be ok
            One reason for making the new slide is that Im not making any permanent changes to it, so if it doesn't work out I can revert to microscope and then go to plan B, which is to run a hollow drawbar in the TOS, and rig up a shaft drive through it for high speeds. It certainly has enough rigidity

            Plus I fancied making a cast iron slide and scraping it in, got to learn somehow

            Just south of Sudspumpwater UK


            • #7
              Other than the rack, that job is made for a shaper.


              • #8
                Quite possibly.
                Fortunately I sold my shaper some years ago, to put in a more useful, more flexible milling machine, which can also do the job without and real hassle, but faster.

                Just south of Sudspumpwater UK