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  • Anyone interested in Metal Scraping?

    Hi everyone,
    as my moniker implies i love to scrape metal!

    What is metal scraping?
    Simply put,
    Metal scraping is a process of precisely removing metal from a surface needing a high degree of flatness, by means of hand tooling or machine driven scraping tools.
    The scraped part is referenced to a known flat surface (i.e. a surface plate) and a spotting ink is used to determine the high spots.
    The high spots are systematically brought to the same plane of contact.
    When 2 scraped surfaces interface with each other, their friction is greatly reduced, especially with the introduction of oil.
    The oil fills the low spots and provides a bearing surface, making the entire assembly float as if it were on glass. here's a picture of a scraped surface.



    In this picture the blue spots are .0015" higher than the low spots!

    Heres a link to my site for more examples!


    if you have interest, i'd like to know!
    thanks for reading!
    Last edited by Metal Scraper; 03-03-2015, 12:54 AM. Reason: spelling

  • #2
    Yes, I scrape. Yes, I love it. Very satisfying bringing worn parts back to precision working surfaces with your bare hands and/or with a biax.
    BTW, you and I are not the only ones.
    Cheers,
    Gary

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    • #3
      This place is crawling with scrapers and several instructors. Welcome to the group.

      Comment


      • #4
        And some of us are scraping wanna-bees. Perhaps scraping gonna-bees.

        Welcome to the group and do share your scraping adventures.
        Last edited by Paul Alciatore; 03-03-2015, 02:32 AM.
        Paul A.
        SE Texas

        And if you look REAL close at an analog signal,
        You will find that it has discrete steps.

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        • #5
          Thank you all,

          looks like i'm in good company!

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          • #6
            Some of us regulars are experienced scrapers of diversified experience. Search the archives using the obvious search terms and you'll find many threads devoted to one aspect of precision scraping or another. You should fit right in.

            What is the casting in your image? The compound mounting plane of a South Bend lathe cross slide? I'd suggest 10 to 16 spots per square inch and a mean ripple of 0.0005" crest to valley.
            Last edited by Forrest Addy; 03-03-2015, 05:05 AM.

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            • #7
              So tell me how this spotting ink business works. Do I put the ink on the surface of the flat or on the workpiece? What is the consistency of the ink, is it fine spirit ink or thick paste like bearing blue?

              Is it the same process as using bearing blue?

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              • #8
                And look out for The Bodger. He is a most artfull dissembler.

                Comment


                • #9
                  Originally posted by The Artful Bodger View Post
                  So tell me how this spotting ink business works. Do I put the ink on the surface of the flat or on the workpiece? What is the consistency of the ink, is it fine spirit ink or thick paste like bearing blue?

                  Is it the same process as using bearing blue?
                  I dunno, but if you have blue bearings, you must be hot stuff..... How do you bear up under that pressure?

                  As for the rest of it, I am pretty sure I have spotted some folks trying to scrape by.... They were heading for a flat, but I am pretty sure they were trying to get a far piece from any work. Per the ink, I suspect they didn't think.
                  CNC machines only go through the motions.

                  Ideas expressed may be mine, or from anyone else in the universe.
                  Not responsible for clerical errors. Or those made by lay people either.
                  Number formats and units may be chosen at random depending on what day it is.
                  I reserve the right to use a number system with any integer base without prior notice.
                  Generalizations are understood to be "often" true, but not true in every case.

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                  • #10
                    If you read the prince you get regal bearing. But don't let your scraper become a scrapper.
                    Steel crazy after all these peers, a can-ode by The High Spots

                    Comment


                    • #11
                      Originally posted by The Artful Bodger View Post
                      So tell me how this spotting ink business works. Do I put the ink on the surface of the flat or on the workpiece? What is the consistency of the ink, is it fine spirit ink or thick paste like bearing blue?

                      Is it the same process as using bearing blue?
                      The ink is spread thinly upon the surface plate with a printers roller.
                      the consistency of the water soluble, Cannode, is very thick a little ink goes a long way!

                      the work piece is rubbed on the inked up surface plate, the high spots reveal themselves readily.

                      Comment


                      • #12
                        Some of us regulars are experienced scrapers of diversified experience. Search the archives using the obvious search terms and you'll find many threads devoted to one aspect of precision scraping or another. You should fit right in.

                        What is the casting in your image? The compound mounting plane of a South Bend lathe cross slide? I'd suggest 10 to 16 spots per square inch and a mean ripple of 0.0005" crest to valley.
                        Last edited by Forrest Addy; Today at 01:05 AM.


                        thank you very much for the information!!

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                        • #13
                          Judging from your pictures and slideshow i would say you use blue to thick. According to the explanations of Nick Mueller on youtube. The darker blue ring around the spot is blue that is squeezed out between the contact points.
                          Otah your post 11 states that you are using something thinner than normal.
                          Is that your way of dealing with this.

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                          • #14
                            Originally posted by Metal Scraper View Post
                            Some of us regulars are experienced scrapers of diversified experience. Search the archives using the obvious search terms and you'll find many threads devoted to one aspect of precision scraping or another. You should fit right in.

                            What is the casting in your image? The compound mounting plane of a South Bend lathe cross slide? I'd suggest 10 to 16 spots per square inch and a mean ripple of 0.0005" crest to valley.
                            Last edited by Forrest Addy; Today at 01:05 AM.

                            thank you very much for the information!!
                            Forrest was my instructor and knows scraping inside out.

                            Comment


                            • #15
                              Originally posted by Metal Scraper View Post
                              The ink is spread thinly upon the surface plate with a printers roller.
                              the consistency of the water soluble, Cannode, is very thick a little ink goes a long way!

                              the work piece is rubbed on the inked up surface plate, the high spots reveal themselves readily.
                              Thank you for being the first to answer my query.

                              When I try this process I dont get any blue on the high spots which show as bright spots with the lows show filled with blue, thats why I asked the consistency of the 'ink'.

                              Apparently the other posters here have never heard of the scraping of Babbit bearings which, IIRC, was done with a thick(ish) blue paste.
                              Last edited by The Artful Bodger; 03-03-2015, 02:48 PM.

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