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Amperage & square inches

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  • Amperage & square inches

    Is the right amperage 1/10 or 1 amp per square inch for annodizing and what is the right way to figure square inches.I have a block of aluminum 2 x 3 x4 inches, some of the face has been machined away but not enough to really make a drastic difference in the square inches. Thanks. vesatr

  • #2
    0.1 amps per square inch.

    To calculate the area of a part, break it down into individual rectangles. The area of a rectangle is Length x Width. Calculate the area for all the rectangles, then add them together.

    Your 2 x 3 x 4 block has 6 rectangles.

    2 with dimensions 2 x 3 = 12 sq in
    2 with dimensions 2 x 4 = 16 sq in
    2 with dimensions 3 x 4 = 24 sq in

    Total Area = 52 sq in
    Mike Caswell
    Caswell Inc
    Need Support? Visit our online support section at


    • #3
      Glad I read this one

      I was about to figure cubic inches and screw something up

      2x3x4=24. 00ps!


      • #4
        I did the same thing and came up with 24square inches.What about a solid 4 inch round 14 inches long ?I have 2 steering cylinders off an oliver tractor that I am going to use the copy chrome set up on . New cylinder rods are 600.00 dollars apiece,I cant afford to make a mistake on them!! Thanks , vesatr


        • #5
          Figuring square inch area for solid round parts:

          (Part diameter in inches x 3.1416) x length = square inches.
          in your case:
          (4 x 3.1416) x 14 = 175.929 square inches

          If the ends are solid and they will also be plated:
          3.1416 x (radius squared) = square inches on each end of round parts.
          in your case:
          3.1416 x (2 squared) = 12.566 square inches (for (1) end)
          12.566 x 2 = 25.132 square inches (for (2) ends)

          175.929 (the "shaft")
          + 25.132 (the shaft "ends")
          201.061 total square inches

          George W.


          • #6
            another quick way to calculate area on flat circles is to remember that the area within a circle is very close to 3/4 of the area of a square or .75 so a 1" circle would be 3/4 sq. inch or .75 sq. inch likewise a 4" circle roughly = 3 square inches ....its so close its easier to calculate it this way unless you have to be absolutely dead on.


            • #7
              correction a 4" circle would be roughly 3/4 of 16 square inches or 12 square inches as:

              4x4 = 16
              16 x .75 = 12


              • #8
                likewise if we round off the 3.142 to just remembering 3 in our area of a tube equation you would come to within aprox tolerances in calculating your amps a 4" solid round @ 14 inches long would be very simple to calculate it this way

                (4 x 3) x 14 = 168 and then add the two flat ends or
                ( area of 4 x 4) x .75 = 12 x 2 two ends = 24
                (add 1st line to second line) = 192 square inches and if each square inch = 1/10 of 1 amp then a total of 19.2 amps using this method which is off by aprox 1 amp or roughly 5% in this example which if I am not mistaken here, would be within tolerances for plating purposes. If so then this breaks the equation and figuring down to a minimum as all you have to do is remember a few easy numbers you can calculate in the noggen or a quick scribble without the use of a calculator.