Lower surface 62 offlange 44 is tapered from the lower edge of undercut 60 to shank 46 of collet 42.After the button is in place on material 14 of an article, such as a garment, it becomes necessary to occasionally wash the garment in warm or hot water, after which it is subjected to high temperature heat in the drying cycle.As shown in FIGS. 2, 3, and 4, because of the larger mass and greater coe