GMNA D143 PDF

GENERAL

This standard for Metric Flat 90° 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 heads proportions of the trim heads were derived by applying to the respective screw diameters the standard flat head diameters the standard flat head diameters applicable to the next smaller screw size.