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  • Removing mill scale

    Hi guys,
    Maybe you have a slick way of removing mill scale from hot rolled shapes, typically bar stock. I have tried wire wheels, 36 grit flap wheels on 4-1/2" angle grinder and 36 grit Roloc discs on a 2" air angle grinder. Wire wheel isn't aggressive enough. Sandpaper cuts thru the scale great for a short period then gets dull and just starts 'polishing' the scale instead of removing it. I've been fighting this for years looking for a better, easier, quicker way. I don't have a blast cabinet, although that would work great.

    Thanks for any tips.

    Craig

  • #2
    I've used Scotchbrite belts on a multitool (belt grinder) with pretty good results. This works if your pieces are small enough to be hand held. I've had the same problems using flap discs, in that, they tend to clog fast.
    Jim

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    • #3
      Actually blasting doesn't work all that great unless you have some very aggressive abrasive and a lot of air capacity.
      Stuffs a pain and I've had no luck removing scale of of large sections.
      Same problems as you have. Wire wheel just knocks off the loose stuff. flap disks clog quick.

      This is one reason I spec cold rolled as much as I possibly can. Or just deal with it.
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      • #4
        36 grit sanding wheels and lots of them. I was getting them for free and cutting them down for my 4 1/2" grinder but that supply dried up....Bob
        Bob Wright

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        • #5
          I gave up on hot rolled! no longer worth the time it costs me.
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          • #6
            I don't remove it.

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            • #7
              Depending on the application I have a couple of different methods. At school I use the belt sander for things like flat bar or the edges of plate. If it is something where cosmetics aren't important I'll just use a 7 inch angle grinder and gently skim the millscale and or rust off.

              Keep in mind neither of these techniques would be the greatest if extremely accurate dimmensions were important. But you would probably be using CRS for that anyway.

              Just my $.02
              Owner of Burnt Beard Fabrication & Welding Ltd.

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              • #8
                It depends.

                If you have a welding engineered drawing, it will specify the requirement. Absent that document, it's kinda up to you.

                For many applications, with the correct rod or wire and gas combination, welding through mill scale is no sweat.

                Working from an egineered drawing would make this advice wrong, but I'm guessing you aren't doing a job shop operation.

                Hank
                ...from the Gadget Garage
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                • #9
                  At least not from a welding engineered drawing. When I started here in 96 nobody removed da scale. I have never seen an engineered drawing to see what the requirement would be. If I had to remove it a grinder on edge works ok if you don't bugger up the metal so the paint won't cover.

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                  • #10
                    Why are you removing?

                    If you are doing to paint, try your pressure washer.
                    When I get ready to paint something, I soak it with simple green or a degreaser and pressure wash it.
                    It will paint up fairly nice.

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                    • #11
                      Muratic acid (pool acid), about half a gallon to a 5 gallon bucket of water small parts. Takes about 20 minutes and it comes out with no scale. For bigger sheets I have sprayed it directly on the sheet, rinsed it after a bit and the scale that is left comes off with little effort with a sander.

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                      • #12
                        Typically only loose or thick mill scale needs to be removed. A grinder works fine for me.
                        "Religion is regarded by the common people as true, by the wise as false, and by the rulers as useful."

                        -- Seneca the Younger

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                        • #13
                          Muratic acid doesn't sound like a bad idea in some extreme cases or when I have larger parts. I'm glad I'm not the only one that fights this. Normally if I'm going to MIG then I don't worry about getting all the scale off down to shiny metal. But now that I have a TIG, I like to get the parts as clean as possible for the best results. Maybe I'm overdoing it but it seems to produce the best results if its 100% clean with the TIG. BTW, this is just hobby type stuff, no production stuff. Thanks for the replies so far guys!

                          Craig

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                          • #14
                            I find that welds made using hardwire turn out much nicer if the millscale is removed first. Better wetting action and a more stable arc. Just my experience.
                            Owner of Burnt Beard Fabrication & Welding Ltd.

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                            4' Box and Pan Break
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                            • #15
                              I second the muratic acid. Spray it on then wash with clean water. Works great in the good ole summertime. Just be quick in getting the water dried off so you dont get a lot of rust.
                              Dennis


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