Cnau rhybed dur di-staen (countersunk / pen gwastad);Pen countersunk / hoelen tynnu pen fflat;Cnau / bollt hecsagon) - beth yw'r rhif safonol cenedlaethol?

Soced hecsagon pen countersunk: GB70.3 DIN7991

Ewinedd tynnu pen crwn agored: GB12618

Cnau hecsagon: GB6170 DIN934

Bollt edau llawn hecsagon allanol: GB5783 DIN933

Cneuen rhybed: GB17880.1