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Lapping Plate: Practical Use and Maintenance?

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  • Lapping Plate: Practical Use and Maintenance?

    I keep getting into situations when I think a lapping plate would be a great asset to my shop. But I have almost no experience with this unless you can count the polishing of a telescope mirror where the lap is made of pitch and the mirror itself is used to form it's curve between polishing sessions. But that is for a curved surface, not a flat one.

    Looking at E-Bay I can see lapping plates that are for sale, often advertised as "As Is". In other words, they are probably not flat. So I have to wonder just how do you know if a lapping plate is flat and how do you correct it if it is not. I can see how a set of three could be worked against each other, but I have not found such a set for sale yet. So I must conclude that most shops do not do it that way. But how? Do they have to rely on outside calibration services, like the guys who will come in and check your surface plate(s)? Or do they just use them until they are no longer flat and then buy another? Or what?
    Paul A.

    Make it fit.
    You can't win and there is a penalty for trying!

  • #2
    For lapping, do they just smear the surface with compound and the slide the part around on the plate?

    The closest I get is wetting some sandpaper and sticking it to some granite counter top material and sliding a part around on top of it.
    Andy

    Comment


    • #3
      Paul, have a look at this video from Tom Lipton. It shows how to lap with a surface plate and some aluminium foil. He checks it on an optical flat at the end. https://www.youtube.com/watch?v=_EypdnIydCg#t=30m20s

      One benefit of this technique is that you won't get different grits embedded into your plate. I think you are meant to have different plates to stop contamination from coarser grits.

      Tom has other videos on lapping, including some where he made his own plates from cast iron and copper washers/coins.
      Last edited by pinstripe; 05-09-2018, 08:22 AM.

      Comment


      • #4
        Had a navy machinist friend that made vibrating laps from cast iron manhole covers.
        He told me he simply filled the lift hole with epoxy and the lap compound would remove the higher epoxy or fill the divot from low epoxy.
        On the bottom side he bolted a motor with eccentric for vibrating.
        One of the uses was lapping piston rings for engines.

        Comment


        • #5
          Originally posted by vpt View Post
          For lapping, do they just smear the surface with compound and the slide the part around on the plate?
          some do, imo the right way with a flat is get your lap flat (grind or scrape) then charge it. The lap becomes a cutting tool and is really never touched so the accurate flat surface remains intact.
          .

          Comment


          • #6
            It seems to me that you should investigate 3M lapping film for use on a surface plate or other flat surface. There is a huge variety of grit sizes bonded to a polyester film backing. Some even have PSA. https://www.3m.com/3M/en_US/company-...94857497&rt=r3
            Amazon sells it and films by other makers as well.

            RWO

            Comment


            • #7
              I second Tom lipton's videos (oxtoolco) on Youtube. There are a number of different videos on lapping, making your own plates, using foil, getting precision granite lapped, etc etc.

              If you have 3 plates, you can get them flat. KBC tool also sells plates for pretty cheap.

              Comment


              • #8
                From the video, it looks like the aluminum foil method would have the same problem as sandpaper where the edges will be rounded. I wonder if a spritz of water under the foil would help.

                Figure eight lapping motion instead of random back and forth would also be more effective.

                Comment


                • #9
                  Originally posted by RWO View Post
                  It seems to me that you should investigate 3M lapping film for use on a surface plate or other flat surface. There is a huge variety of grit sizes bonded to a polyester film backing. Some even have PSA. https://www.3m.com/3M/en_US/company-...94857497&rt=r3
                  Amazon sells it and films by other makers as well.

                  RWO
                  Yup, same here. Micro film and an enco surface plate. Works well for me and is clean to work with. JR

                  Collected over 20 years. Some very fine stuff in the pile.
                  Last edited by JRouche; 05-09-2018, 03:11 PM.
                  My old yahoo group. Bridgeport Mill Group

                  https://groups.yahoo.com/neo/groups/...port_mill/info

                  Comment


                  • #10
                    Originally posted by pinstripe View Post
                    Paul, have a look at this video from Tom Lipton. It shows how to lap with a surface plate and some aluminium foil. He checks it on an optical flat at the end. https://www.youtube.com/watch?v=_EypdnIydCg#t=30m20s

                    One benefit of this technique is that you won't get different grits embedded into your plate. I think you are meant to have different plates to stop contamination from coarser grits.

                    Tom has other videos on lapping, including some where he made his own plates from cast iron and copper washers/coins.
                    Thanks for linking that video. Love the foil lap idea, and also the mini granite block for the surface grinder is genius. I want/need one.

                    Comment


                    • #11
                      Originally posted by elf View Post
                      From the video, it looks like the aluminum foil method would have the same problem as sandpaper where the edges will be rounded. I wonder if a spritz of water under the foil would help.
                      Later in the video he says that he is experimenting with foil tape.

                      Comment


                      • #12
                        I hate links to pages that do NOT show prices. Those things must cost $1,000,000 per sheet. No sale! No interest! I am instantly turned off by any company that can not tell me what their product costs. UP FRONT!

                        PS: the last 3M professional product that I purchased in any quantity was 2" video tape. It was mediocre quality but one of the most expensive brands on the market. They hid the price for that too. I am not a big 3M fan. I don't like sales tactics that hide facts.

                        Sorry, but after looking for a price that could not be found, I got into rant mode. 3M got a message to that effect also.



                        Originally posted by RWO View Post
                        It seems to me that you should investigate 3M lapping film for use on a surface plate or other flat surface. There is a huge variety of grit sizes bonded to a polyester film backing. Some even have PSA. https://www.3m.com/3M/en_US/company-...94857497&rt=r3
                        Amazon sells it and films by other makers as well.

                        RWO
                        Paul A.

                        Make it fit.
                        You can't win and there is a penalty for trying!

                        Comment


                        • #13
                          Originally posted by Paul Alciatore View Post
                          I am not a big 3M fan. I don't like sales tactics that hide facts.

                          Sorry, but after looking for a price that could not be found, I got into rant mode. 3M got a message to that effect also.
                          Yer loss, not theirs. Their have some of the best abrasives on the market.

                          And yes, their Imperial Lapping films are very expensive. So maybe not for you. Understandable. JR
                          My old yahoo group. Bridgeport Mill Group

                          https://groups.yahoo.com/neo/groups/...port_mill/info

                          Comment


                          • #14
                            That is a very interesting video. I may have to watch it again.



                            Originally posted by pinstripe View Post
                            Paul, have a look at this video from Tom Lipton. It shows how to lap with a surface plate and some aluminium foil. He checks it on an optical flat at the end. https://www.youtube.com/watch?v=_EypdnIydCg#t=30m20s

                            One benefit of this technique is that you won't get different grits embedded into your plate. I think you are meant to have different plates to stop contamination from coarser grits.

                            Tom has other videos on lapping, including some where he made his own plates from cast iron and copper washers/coins.
                            Paul A.

                            Make it fit.
                            You can't win and there is a penalty for trying!

                            Comment


                            • #15
                              Oh, I will get over it.



                              Originally posted by JRouche View Post
                              Yer loss, not theirs. Their have some of the best abrasives on the market.

                              And yes, their Imperial Lapping films are very expensive. So maybe not for you. Understandable. JR
                              Paul A.

                              Make it fit.
                              You can't win and there is a penalty for trying!

                              Comment

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