I don't know the OD, but in the past I have taken a long stainless steel bolt, cut off the threaded section and round off the head on a bench grinder. Henry probably used some weird odd size. Or go to Snyder's Antique Auto Parts. Hinge Pins With the round head authentic for the closed cars. Available in the original size (.233/.236) or in oversize (.247/.250). These fit 1928-31 Closed body styles except Slant Windshield cars.... Part Number Specifics Price A-46335 Standard Size $0.39 / ea. A-46335-OS Oversize $0.39 / ea. A-46335-OS-Q6 Oversize Set of 6 $1.75 / set A-46335-Q6 Standard Size Set of 6 $1.75 / set