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  • Smoothest mill file

    Hello All,

    I'm looking for a source for a mill file to do the smoothest possible job of filing the edge of woodworking "card" scrapers. Mine are .025" X 3" X 5", hence the name "card". Sharpened to a highly polished edge these simple hand scraping tools are one of the most useful tools in a guitar maker's shop.

    The problem comes when re-sharpening. The process of burnishing the edges at a 10° angle to produce the burr that does the cutting makes a small bevel. I use a couple of DMT diamond stones---45 micron and 9 micron---to polish the edges and faces of the scrapers, but it takes a lot of time to hone down past the bevel created by the burr making process.

    Draw filing with a 6" smooth mill file---the finest toothed file I have---leaves quite a rough edge that still needs a lot of work to bring it to a nice crisp polished corner, ready to be burnished. I'm willing to spring for a high quality super smooth mill file (a Grobet?), I just need to know what to ask for, and where to buy one.

    Many thanks,

    Brian Burns

  • #2
    Maybe try some wet/dry paper of an appropriate grit on a flat surface?
    Location: Long Island, N.Y.

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    • #3
      There is a dead smooth file
      Mark

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      • #4
        Originally posted by RichR View Post
        Maybe try some wet/dry paper of an appropriate grit on a flat surface?
        Hello Rich,

        The idea of filing is to remove stock quickly. I can work my way down through the bevels in about 10 minutes each of sweating, using my 45 micron stone, where a file will get me through them in 30 seconds. I have a 120 micron (closely 120 grit) stone that does it fast enough, but leaves a lot of work left to do on the finer stones. The scraper steel is Rockwell 48-52.

        By the way, for years I've used 60 grit wet or dry silicon paper on glass to flatten my soft Japanese water stones. As a sharpening medium it wears out really fast. Diamond honing stones are the only practical thing for a woodworker trying to make a living at it.

        Cheers,

        Brian

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        • #5
          Originally posted by boslab View Post
          There is a dead smooth file
          Mark
          Hello Mark,

          Yes, I've read of the existence of such a beast, but I'm at a loss as to where to find one.

          Cheers,

          Brian

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          • #6
            This method wouldn't cut it? http://www.liutaiomottola.com/Tools/Scraper.htm

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            • #7
              Try "Bahco" for the dead smooth, may have to go via Europe.

              Just looked, about half of their offered needle files can be got in "dead smooth" (nothing that I could see in the regular hand files was dead smooth)
              Last edited by RussZHC; 02-24-2015, 03:10 PM.

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              • #8
                Hello Rosco-P,

                R.M. Mottola is a friend, but I hadn't thought to check his website to see his scraper sharpening method. I don't do his initial drawing out the burr somewhat by burnishing the face of the scraper first. That step might be a workaround to avoid producing the bevels in the first place. Thanks for the tip (:->)...

                I have a point-and-shoot camera coming tomorrow that will focus very close-up. I'll see if I can take some photos at various stages, and blow them up to see what's really happening.

                Cheers,

                Brian

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                • #9
                  It came up in a search, near the top by the way. I'm no fine woodworker, but recall reading in FWW long ago that sharpening cabinet and card type scrapers was supposed to be quick and easy. Having to stone the edge just seems too time consuming for a commercial or production shop.

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                  • #10
                    I may be missing something here, but it should not take that long to sharpen a card scraper. At least not one with a straight edge.

                    http://www.finewoodworking.com/tool-...d-scraper.aspx

                    Perhaps you are going at it too aggressively. If the previous burr was only a few thousandths wide and at a 10 degree angle, then you should only need to remove a few ten thousandths of metal to get down below it. That would go fairly quick on almost any stone or abrasive paper. Or just a few light strokes with a file.
                    Paul A.
                    SE Texas

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

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                    • #11
                      So called "pivot files" are the finest, smoothest cut files I've ever seen, and I think would leave you with a surface that would easily burnish. The potential issue is that I've never seen a pivot file longer than 2.5" or so. They can be difficult to find, I'm not sure if they are still manufactured but old ones are out and about if you keep your eyes peeled.
                      Max
                      http://joyofprecision.com/

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                      • #12
                        Hello Roscoe, Paul and Max,

                        Sharpening a card scraper to a high polish raises its usefulness to a much higher level. I make classical guitars, and I can scrape hardwoods to a surface ready for French polishing---no sanding required. And it's fast. Guitars are mostly curved surfaces, and scrapers will follow curves.

                        Softwoods don't like to be scraped, though cypress is hard enough that it will scrape Ok, if I'm not too aggressive.

                        In the 1960's I was first taught to sharpen a scraper by draw filing with a mill file (single cut), and then burnishing out a hook with a hardened steel rod used just on the edge. That worked fine for rough work, but always left a surface requiring a good deal of sanding because the filing scratches appeared in the burr.

                        Some 30 years ago I developed a sharpening system for hand plane irons called "Double Bevel Sharpening", and was teaching a class in it at the Japan Woodworker in Alameda CA when a student asked about sharpening scrapers. I said I didn't use them much as they were pretty crude tools. I went home thinking that I had given a pretty poor answer to the student's question, and that perhaps I could come up with a better sharpening system for scrapers.

                        I developed a couple of tools for polishing the edges and faces of scrapers to a 9 micron (1200 grit) finish. Then I've been using my burnisher only on the edge to roll out a burr. The resulting wood surface is both crisp in appearance and very smooth. The problem comes when re-sharpening, and it's just a time problem.

                        My Veritas edge burnishing tool is set to a 10° angle, and working on a crisp square corner it not only forms out a burr, but makes a small bevel. If I work long enough with my edge dressing tool, I can get back to a crisp square corner. My thought about filing with a really smooth mill file is that I can cut the time down for getting back to a crisp, square corner.

                        The suggestion that I look at R.M. Mottola's scraper sharpening method has brought out a possible way to avoid making the little bevels that need to be gotten through when re-sharpening. He burnishes the faces of the scraper first, which I had seen done before, but he does it at a very slight angle so as to form out a burr that is vertical to the edge. I had not noticed the very slight angle. He then burnishes from the edge, turning the burr down parallel to the edge---no bevels, if his drawings are an accurate representation of what is actually happening.

                        If this all seems like a lot of huffle and kerffufle for a small reward, I can assure you that working with a really sharp scraper is one of the more pleasurable things in woodworking (:->)...Now, if I can just speed up the sharpening process...

                        Thanks for all your helpful suggestions,

                        Cheers,

                        Brian

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                        • #13
                          Just throwing out ideas. If you could touch up the edges to a perfect 90 via a surface grinder might that work? Honing machines typically used with scissors wouldn't give the accuracy or surface finish needed?

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                          • #14
                            Hello Roscoe,

                            I would LOVE to have a surface grinder! But I took the vows of poverty when I decided to be a guitar maker, and it's well beyond my means...

                            I took a wonderful machine shop course at Mount San Antonio College in Pomona, CA back in the 1960's, and the surface grinder was one of my favorite machines top use.

                            BTW, I learned a lot about woodworking in that class. Feeds, speeds, cutting angles, chip load per tooth, heat dissipation---they have all been useful in woodworking. In fact, my sharpening system is based on the understanding of the importance of cutting angles that I got from that class. Google "double bevel sharpening" and you will get a link to my youtube video on it.

                            Cheers,

                            Brian

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                            • #15
                              the finest cut files I have used are #6 cut Swiss files.

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