Experiment reseach about involute gear’s tooth form factor and stress correction factor by applying 30o tangent method is carried out. Tooth profile generating experiment to teeth number is carried out

measury tooth root chord at the critical section SFn

bending moment arm for root stress hFa and root fillet radius of tooth ρF are measuried

and diagrams of involute gear’s tooth form factor and stress correction factor are given. Design resourse for involute gear’s strenth design with a small number of teeth is supplied.