mulepackin
Well-known member
Just curios if anyone knows the history behind the standard drive sizes. Even European manf. use SAE dr. sizes, never seen a metric drive.
kartracer55 said:No Idea why, but they also had, at one point, a 5/16 drive size. I have one socket. My boss has a small baby wipe box in his box full of super old snap on stuff, some of it going back to the 40's if not earlier. He has a few 5/16 drive tools as well.
Many people don't realize this, but up until a certain point somewhere between the 40s and the 70s... ALL automobiles made EVERYWHERE used fractional fasteners. There were no metric nuts or bolts used in vehicles.mulepackin said:Just curios if anyone knows the history behind the standard drive sizes. Even European manf. use SAE dr. sizes, never seen a metric drive.
goodfellow said:Same with automotive rim sizes. Even though tire tread sizes are now international metric, the rims are still sized in inches. There were a few attempts at metric rims back in the late 80's, (used by Ford and others), but that faded fairly quickly.
TNToy said:Many people don't realize this, but up until a certain point somewhere between the 40s and the 70s... ALL automobiles made EVERYWHERE used fractional fasteners. There were no metric nuts or bolts used in vehicles.
To top that off, the Ratchet & Socket idea was invented here and spread abroad by Snap-On... although they didn't actually invent it. So it started with SAE sizing, and everything has stayed that way to ensure compatibility.
Oh, and 1/2" is NOT 12mm. It actually works out to 12.7mm.![]()
TNToy said:Many people don't realize this, but up until a certain point somewhere between the 40s and the 70s... ALL automobiles made EVERYWHERE used fractional fasteners. There were no metric nuts or bolts used in vehicles.

TNToy said:Mainly I'm referring to the period of time where about 99.7% of the vehicles found in the US were either made in the USA, or they were British.
Jbullfrog said:Ford was the best at randomly combining Metric and Standard fasteners on vehicles. Standard on the engine, metric in the cab, metric on the rear axle, standard on the front axle and hubs.