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  • casting sanding blocks

    Does anyone have any experience casting sanding blocks out of polyurethane or similar products. I have a lot of doors with beads to be refinished and I'm looking at making sanding easier.
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  • #2

    Re: casting sanding blocks

    Dave.. years ago I used “Bondo” for shaping a sanding block for some molding I had made. The molding was not very intricate, no beads, but the block worked fine for its purpose. Roy
    dave_k likes this.
    Are you solving the problem, or becoming part of it?

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    • #3

      Re: casting sanding blocks

      I had never considered making cast sanding blocks. Brilliant!
      beachburl likes this.

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      • #4

        Re: casting sanding blocks

        How do you allow for the thickness and stiffness of the sandpaper when preparing the mold? Maybe using your Dremel tool to modify the blade in a paint scraper to match the molding. I have used this with mixed results.

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        • #5

          Re: casting sanding blocks

          Originally posted by ofoori View Post
          How do you allow for the thickness and stiffness of the sandpaper when preparing the mold?
          This is why I'm asking for other woodworkers experience. I know many years ago I saw kits for casting sanding blocks for inline sanders. I haven't seen them recently however it seems like a good idea as long as small issues like this can be overcome. I'm looking for ideas and pitfalls .... one of which you kindly pointed out. Thanks.

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          • #6

            Re: casting sanding blocks

            I would try a mop first.

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            • #7

              Re: casting sanding blocks

              Cast with the sandpaper.
              wooden die, sandpaper, Saran Wrap, bondo, back block and clamp.

              The bondo is a good idea. Be aware that it has a very short set up time.

              Could experiment putting a thin foam pad on the bondo.

              l have made a course thread nut using bondo pressed into a die. It works but strength is untested.
              dave_k likes this.
              Egon
              from
              The South Shore, Nova Scotia

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              • #8

                Re: casting sanding blocks

                See #4---------- scraper.
                "Do it Right!"

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                • #9

                  Re: casting sanding blocks

                  Thanks Rusty, I do that already. What I'm looking for is peoples experience casting sanding blocks to make custom profiles.

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                  • #10

                    Re: casting sanding blocks

                    I have a number of detail sanders. I have a collection of store bought tadpoles and custom custom made scrapers and sanders.

                    What I want to do is to try casting some sanding blocks with pourable rubber / plastic as a simple project to gain some experience in casting. There is a vast range of casting materials on the market from polyurethanes to EVA Urethanes, none of which I have any experience in. The best sanding blocks are made with EVA rubber. I've found pourable EVA neoprene used in the theater to make "creatures" but I don't know if this formulation is going to be suitable for sanding blocks.

                    What I was hoping for is someone with some experience in working with these materials that was willing to share.

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                    • #11

                      Re: casting sanding blocks

                      I have used bondo a lot to make castings (not sanding blocks) I have cast a lot of shapes on boats so I have the opposite male / female so I can then use the casting with a copy cutter on a router to obtain the exact fit, I usually rough cut mdf, plastic tape the object to be copied neatly then hold the mdf colse by say 5mm gap and fill the gap with bondo overnight it gets a good grip of the mdf and breaks away from the plastic tape, sand the faces and use the bondo cast edge to run a router ball race on walla a perfect fit unless its an internal square corner,
                      I used this at home when I wanted a carpet piece under some doors, that's a piece of wood clear finished between the door frame that wraps around both sides to line up with the outer edge of the architrave, I neatly plastic taped the painted door frame and floor at both ends I cut a mdf strip just short by 10mm and wider than the final wood I was going to use I held it in place and filled the ends with bondo, you could do the mdf in half for ease of removal, then place the mdf on the nice grain floor piece / threshold and copy with router, it becomes difficult if when sliding it down the finishes paint the door frame is different higher up. just rambling on a wet morning.

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                      • #12

                        Re: casting sanding blocks

                        OK, Understood. Check out the COPER.. Dig up a video and watch how they cast with a 2 part. I've posted how I do baseboard coping with a router many times on this forum.
                        "Do it Right!"

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                        • #13

                          Re: casting sanding blocks

                          Silicon might work. ??
                          Egon
                          from
                          The South Shore, Nova Scotia

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                          • #14

                            Re: casting sanding blocks

                            Therre are rigid casting rubbers that would likely work (eastwood company used to make some to allow you to duplicate the pads that are on brake pedals etc. but there are other manufacturers like Devcon Flexane). My concern would be allowing for the thickness of sanding paper? I think just sticking the paper to the cast form would change the profile of the wood during sanding?? Its an interesting idea if you can make it work.

                            Maybe lining the profile with some paper, then casting over the paper would allow you to more closely follow the form?
                            Last edited by scooby074; 01-15-2019, 06:25 PM.

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                            • #15

                              Re: casting sanding blocks

                              Originally posted by scooby074 View Post
                              My concern would be allowing for the thickness of sanding paper? I think just sticking the paper to the cast form would change the profile of the wood during sanding?? Its an interesting idea if you can make it work.

                              Maybe lining the profile with some paper, then casting over the paper would allow you to more closely follow the form?
                              I was thinking of maybe fine tuning the mold with files / abrasives then using using lightweight automotive paper. Those casting products you mentioned ..... would NAPA carry them?

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