Design of tools for press-countersinking or dimpling 0.040-inch-thick-24S-T sheet

Templin, R L (Aluminum Company of America) Fogwell, J W (Aluminum Company of America)
naca-tn-854
August 1942


A set of dimpling tools was designed for 0.040-inch 24S-T sheet and flush-type rivets 1/8 inch in diameter with 100 degree countersunk heads. The dimples produced under different conditions of pressure, sheet thickness, and drill diameter are presented as cross-sectional photographs magnified 20 times. The most satisfactory values for the dimpling tools were found to be: maximum punch diameter, 0.231 inch; maximum die diameter, 0.223 inch; maximum mandrel diameter, 0.128 inch; dimple angle, 100 degree; punch springback angle, 1 1/2 degree; and die springback angle, 2 degree.

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http://naca.central.cranfield.ac.uk/reports/1942/naca-tn-854.pdf