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  • #16
    I'm going to get right on this - well, maybe tomorrow. I've never tried it, although I'd heard about it and I always thought it made good sense.

    Do you use full strength, concentrated, muriatic. That's 35 % by weight, HCl in water, isn't it ? Or will a diluted from work as well. If vinegar works, I'd have thought muriatic diluted would work.

    My grandmother would use vinegar with salt in it when she wanted to get heavy with something. I mean an article of culinary equipment, before anyone starts getting funny ! I guess the salt increases the ionisation of the vinegar, maybe even making it more acidic. It seemed to help.

    On our side of the pond I believe we call muriatic acid by the name hydrochloric acid.

    On that note, as my daughters go through school learning chemistry, I'm struck by how many chemicals have been given new names since I was a kid. Like acetic acid is now ethanoic acid, ethylene is now ethene. When I want to get my own back, I hit her with oil of vitriol or muriatic acid - not literally I mean, or do I mean literally after all ?
    Richard - SW London, UK, EU.

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    • #17
      I take old rusty files and "rebreak them in" by filing aluminum or brass. The aluminum is sticky enough to take off the rust, and brass being soft does the same, though not as good initially. Has worked for years, just like breaking in a saw blade.
      CCBW, MAH

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      • #18
        Years ago, I had one of those tool boxes you could stand on. Inside it was a file that was smooth if you get my drift.

        I used it with a concrete block to set a laser level on and never got around to moving the box back into the garage for a year or so.

        When I opened the tool box, step stool, I found it full of water with a very black colored file that was far sharper.

        There is something to acid treatment of files that has merit.

        Clutch

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        • #19
          ive got a wire brush mounted on a bench grinder ...does a good job ...always follow the angle of the lines if the file with the brush.

          i would think muric acid would eat away and round off the fine sharp edges on the file.

          all the best.markjj

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          • #20
            strange you say that i was always told never to run a wire brush on a file it is said to ruin it maybe you know something i dont

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            • #21
              No one's posted why these methods work.

              Imagine the shape of a (slightly blunt) sawtooth - you know, a triangle with one vertical side, the horizontal edge being part of the main blade.

              Now immerse said tooth in whatever is going to chemically attack it, be it acid or just impure rain water and oxygen.

              The corrosion happens on the flat surfaces - the tip doesn't 'exist' for the purposes of corrosion - it's just the conjunction of two surfaces.

              If you started with a sharp tip, corrosion would hollow the flat surfaces and give you a hollow-ground tip.

              So as the slightly rounded surfaces get eaten away the result is that the blunt tip gets sharper.

              It's the same process used in the old days by high-acutance photographic developers for enhancing sharpness.
              Richard - SW London, UK, EU.

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              • #22
                When you get done with the muritic acid, don't store the sealed bottle in your shop anywhere near your machine tools. I have always been told it will rust them even if tightly sealed. May not be true, but I wouldn't take the chance.

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                • #23
                  Originally posted by Mac1
                  When you get done with the muritic acid, don't store the sealed bottle in your shop anywhere near your machine tools. I have always been told it will rust them even if tightly sealed. May not be true, but I wouldn't take the chance.
                  Yep, happened to me. I had a plastic bottle of the stuff in the corner and all the tools on the pegboard in that section got rusty, (but the files got sharp )
                  Last edited by AiR_GuNNeR; 06-12-2010, 10:32 AM.
                  Eric Sanders in Brighton, Michigan
                  www.scope-werks.com
                  www.compufoil.com

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                  • #24
                    After getting some advice here on this forum as regards de scaling hot rolled plate I tried Phosphoric acid as sold as cement and brick cleaner, mixed 4:1 with water it takes overnight to remove the scale and leave a gray sheradised finish.

                    Not tried it on files, will do over the weekend and report back.
                    I reckon it will work well as when I was setting up I found a tap in the base of a machine that had probably been there 30 years or more all rusted up. Soaked it overnight and next day it was perfect and even felt as if it had a burr to the teeth.

                    Good thing about Phosphoric acid is that it's not a nasty acid, you can tip it on the yards afterwards and hose it down the drain, lets face it, that's what it was made for.

                    Also it doesn't fume, I have an open topped plastic tray holding about 4 gallons at the side of the horizontal mill. It's been there 6 months or so, no rust what so ever.
                    .

                    Sir John , Earl of Bligeport & Sudspumpwater. MBE [ Motor Bike Engineer ] Nottingham England.



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                    • #25
                      john, here in the U.S. phosphoric acid is sold in grocery stores as a bathroom cleaner for brightening porcelain toilets ,sinks, and tiles. Sani-Vac i think its called. also a cleaner for AC coils sold at ace hardware. i use it to blacken shiny,fresh-machined metal parts. i will try it on some files. i heard about acid etching files many years ago but never tried it. when i was a boy in the mid-sixties my great grandfather had 30-40 different files,each for a special metal type. he cleaned his files with a file card and either bar soap or chalk. a very simple tool that no one knows how to use anymore since grinders got so cheap. and no one knows how to use those either.

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                      • #26
                        Back in the '50's I knew a company that used acid (nitric I think) to re-sharpen the flexible curved tooth files which were widely used by auto body shops at that time. They then hard chromed the files.

                        Acid etching will definitely create sharp edges. I once took a Pierce-Arrow valve cover to a chrome shop to have the chrome removed and they left it in the bath too long. I severely cut my finger before I realized that all the edges had become knife edges.
                        Don Young

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                        • #27
                          I have to wonder, though, why just putting the file outside to rust doesn't perform the same "sharpening" that an acid bath does ? Perhaps if the rusty file were thoroughly cleaned with a brass wire brush , you would remove the rust on the flat tooth surfaces, and leave the sharp edge exposed, as with an acid bath. Perhaps the acid simply does a faster and easier job of removing the unwanted rust between tooth edges ?
                          Phosphoric acid is readily available at auto supply stores, as it's used to remove surface rust and prepare steel auto body parts for painting, and it also leaves a thin gray phosphate coating behind to help prevent further rust.

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                          • #28
                            I'll stick with vinegar, it's cheap and its forgiving. The file you forget about and leave in vinegar for a week will still be there, and and will be very sharp.
                            Jim

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                            • #29
                              Originally posted by rohart
                              I'm going to get right on this - well, maybe tomorrow. I've never tried it, although I'd heard about it and I always thought it made good sense.

                              Do you use full strength, concentrated, muriatic. That's 35 % by weight, HCl in water, isn't it ? Or will a diluted from work as well. If vinegar works, I'd have thought muriatic diluted would work.

                              My grandmother would use vinegar with salt in it when she wanted to get heavy with something. I mean an article of culinary equipment, before anyone starts getting funny ! I guess the salt increases the ionisation of the vinegar, maybe even making it more acidic. It seemed to help.

                              On our side of the pond I believe we call muriatic acid by the name hydrochloric acid.

                              On that note, as my daughters go through school learning chemistry, I'm struck by how many chemicals have been given new names since I was a kid. Like acetic acid is now ethanoic acid, ethylene is now ethene. When I want to get my own back, I hit her with oil of vitriol or muriatic acid - not literally I mean, or do I mean literally after all ?
                              We call it the same here, the stuff I use I bought cheaply from a hardware chain, it's used to clean mortar as I believe it reacts with the strongly caustic mortar. I'd suggest you'd have a hard time "forgetting" about a file in there as it only takes a few minutes, and despite best laid plans the smell that invariably will drift over you will remind you I'd love to know just how much potential those fumes have for significant harm.

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