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Physics lesson needed.....abrasive cut off performance

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  • Physics lesson needed.....abrasive cut off performance

    Often when cutting off larger thicker steel with an abrasive (made for steel) 14" cut off the sparks and cutting stop and the steel gets hot.

    I can detect the the "blade" is hot but only for a very short time.

    Even after the blade and steel cool several min. it will not cut unless I wait for a long period of time, about an hour it will cut again.

    I know the problem is the blade cause if I put in a fresh blade I can cut immediately.

    What is going on?

    going to go try to finish the cut in a 3/16" x4"

  • #2
    I have the same thing happen. The blade gets a glaze on it and it won't cut. Try cutting some thinner or light gage material to remove glaze.

    Comment


    • #3
      If you don't push down consistantly it helps. Like alternating between pushing down & letting up on the handle. I have also flipped the abrasive disc around. Just make sure it isn't directional. You can also try a lube while cutting. Sometimes I use wax (http://www.mcmaster.com/#lubricant-stick-wax/=l7zxs1) or wd-40.

      Sorry can't give you the physics lesson.

      Comment


      • #4
        When cutting flat bar in an arbrasive saw try cutting it standing up verses it laying flat, I would always keep steady pressure, If you let off in the midddle of a cut the steel hardens and when you start back you have to heat it back up again before it wants to cut.

        I wouldnt put any oil on the blade ( You dont want it to deteriorate and shatter).

        If your cutting it in a band saw then you want to lay it down flat.

        Comment


        • #5
          Purchasing quality wheels is important too. I am yet to find anything that works as good as Sg Elastic products.

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          • #6
            The lower quality disks are especially bad. The grit glazes and stops wearing away, thus just making more heat. When I used to use a chop saw alot, I had a piece of spring steel that I would touch to the disk and break the glaze off so it would keep cutting.

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            • #7
              I try to keep the surface area of the cut as small as possible. The example of flat stock works well for me. Also, c-channel I'll stand on end and I do that with smaller angle iron (1.5"x1.5"). "pulsing" the pressure helps and I try to keep the RPMs up on the blade. I have been using the diablo 14" abrasive cutoff blades and they have been decent. Readily available. I think part of it is just practice? Finding the fastest and most efficient way to cut without damaging the parent material.

              Good luck.

              Comment


              • #8
                Those big abrasive wheel cutters suck. I hate em. I only use mine now if I can't cut the piece with either a Porta-Band saw or a small cutting wheel on an angle grinder...which means "almost never."

                I think I'd rather try to chew through the cut with my teeth than use a 14" abrasive cutter.They take forever, they make a racket and they usually make a lousy cut.

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                • #9
                  Seems like the long life blades are the worst for glazing try a fast cut blade the fast cut are getting harder to find I think the last one I got was at grainger.

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                  • #10
                    Originally posted by benA View Post
                    The lower quality disks are especially bad. The grit glazes and stops wearing away, thus just making more heat. When I used to use a chop saw alot, I had a piece of spring steel that I would touch to the disk and break the glaze off so it would keep cutting.
                    Second that, just like steel can be hardened, the grits on the wheel can get "hardened" Think of it more as using a hole saw through plastic. If you use a 3" hole saw to drill through 1" plastic with a lot of pressure and speed, you will melt the plastic, and once it gums up on the teeth, you will never cut until the teeth are cleaned.

                    I would just use another piece of metal and "clean" the wheel, and keep going. I never did try switching the blade around, that seems like a good idea.

                    Comment


                    • #11
                      I realised over the years that on a 14 inch blade only the firts 2 inches are made of decent abrasive...
                      Is that because there are more fibre the closer you get to the arbor or because no matter the constant rpm of the saw a 10 inch blades has much less inch per minute of abrasive working on the surface... 14 x 3.1416 x rpm = ipm when it's reduced by 40% and fibers are added...

                      Over the years we tried so many brands even the walter representative made me try his whole assortment with limited failure or success. Add to that that some (most) cheaper blades are of poor quality and reinforcment inside is not always center and never cut straight, i have a home made saw driven by a 5 hp motor wich work best with mid priced blades (1/4 x 6 flat and straight when blade is worn less than 10 inches, or 3/8 x 2 1/12 flat cold rolled 4 stacked).

                      Performnce wise, not bad! but the dust.... I plan to go dry cut but fear the noise...

                      Comment


                      • #12
                        Here's the physics:

                        The cheapo wheels use abrasive grit that melts VERY NEAR the melting temperature of the target metal (steel, usually), or grit with impurites that melt BELOW steel's temp. So when the kerf gets hot, the cheap grit liquefies instead of the metal, but the grit sticks to the wheel (UNlike the steel flakes, which oxidize & shrink rapidly as they go around the backside of the wheel & flake off), so you make no progress. If you have a diamond truing tool for your bench grinder, you can use that (or maybe a common quartz stone) to break the glazed grit & expose more fresh abrasive, but the only real fix is to buy high-quality name-brand wheels.

                        Comment


                        • #13
                          Let the wheel cool

                          I find that the best way to prevent the problem you describe is to not let the wheel get too hot. If I have a big cut, I will pull down for a few seconds, let up a few seconds, pull down a few seconds, etc. Ever since I started doing it that way, I no longer have the problem you describe.

                          I will say that 1 inch square is about my limit for the abrasive wheel. If I have to cut 1/2 inch by 1 inch, I put it on edge, go up and down until I get through it. They work a lot better for 1/4 inch thick material, but always put the material on edge. I think that I could probably cut 2 inch by 1 inch material by putting it on edge, and just taking my time.

                          I use my abrasive wheel a fair amount, so I have some experience.

                          My two cents.

                          Richard

                          Comment


                          • #14
                            Thanks for all the responses....some good advice

                            The "blade" that mad me write this thread is Pferd. made for steel.

                            I have been using this cutter about 20 years. I have already been using many of the methods described here. One I have not tried is setting the materiel on end.

                            I have about 200 (see them on craigslist all the time, I usually pay less than a dollar each) of these abrasive cutoff wheels of various brands. Some deteriorate faster than others but they all seem to "clog" about the same.

                            I agree that is it is a noisy messy not precession cutting device, but for cheep cutting it is the way to go.

                            I also have a Milwaukee 14" dry cut........really NICE cuts, I have cut a 9lb 5" channel where drop could only be measured with a micrometer, but the blades are EXPENSIVE!


                            I would list all my tools but you guys would just cry.

                            Thanks for all the replies!

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