GENERAL

This standard for Metric Flat 90^o countersunk Head 6-Lobed Socket Tapping Screws of thread forming Types AB and B and thread cutting Types BF and BT conforms in all essentials, except driving provisions, with the American National Standard covering metric tapping screws. Basically, the smaller head proportions of the trim heads were derived by applying to the respective screw diameters the standard flat head diameters applicable to the next smaller screw size. It should be noted that for the most part, the Type 1A cross recess configuration will serve to identify the screws as being metric.