. American engineer . ching a hole in a plate, the total area of shearing isthat of a curved surface—of a cylinder of a length equal to thethickness of the plate (t) and a diameter equal to the diameterof the hole (d). Assuming a plate of 60,000 lbs. tensile strength,the resistance due to shearing is T X t X d X 60,000 1 It has been found, experimentally, that in punching plates. This value multiplied by the number of holes punched aminute and divided by 33,000 gives the horsepower for thepunching alone. To this must be added the friction of themachine and the efficiency of driving. Let S = Te
. American engineer . ching a hole in a plate, the total area of shearing isthat of a curved surface—of a cylinder of a length equal to thethickness of the plate (t) and a diameter equal to the diameterof the hole (d). Assuming a plate of 60,000 lbs. tensile strength,the resistance due to shearing is T X t X d X 60,000 1 It has been found, experimentally, that in punching plates. This value multiplied by the number of holes punched aminute and divided by 33,000 gives the horsepower for thepunching alone. To this must be added the friction of themachine and the efficiency of driving. Let S = Tensile strength of the plate = 60,000 lbs. d =: Diameter of the hole, t =: Thickness of the plate. E = Effective depth of entrance of punch to shear the plate = /i. N = Number of holes punched a minute. C = Efficiency of punch (assumed to be 75 per cent.). Cm = Efficiency of motor or drive (assumed to be 80 per cent.). Combining (1) and (2) and allowing for the efficiency of the machine and drivinp; mechanism we have. Horse Power Required to Punch Holes in a Steel Plate of 60,000 Lbs. Tensile Strength. of the tensile strength gi\en, wiien the punch has passed one-third the distance through, the material is all sheared off. Assuming the resistance to be constant during the process ofpunching, the work in foot pounds necessary to punch onehole equals the resistance in pounds per square inch times 1/3the thickness of the plate, divided by 12, or as given above, ir X t X d X 60,000 X t X N X E33,000 X 12 X .75 X 80Cancelling and reducing, we havet= X d X N formula is the basis on which the accompanying diagramis constructed. 1913. RAILWAY AGE GAZETTE. MECHANICAL EDITION 373 W hen using the diagram the reiiuircd thickness of the plateis taken on the scale at the left, and the line is followed hori-zontally to the right, to its intersection with the diagonal fordiameter of hole; thence vertically downward to the diagonalfor number of holes punched a minute, and then
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectrailroa, bookyear1912
