This is kind of a trivia question I don't know the answer to. I am curios about the use of lock washers on Model T's and the rest of the industry of that era. The Model T had very few lock washers and a lot of castellated nuts. When the Model A came out, it had some castellated nuts and used a lot of lock washers.
I can think of only two places lock washers were used on '09-'16 Model T's. (2)9/16" where the rear radius rods meet the drive shaft tube and (2)#20 if the car came with a clamp on style speedometer drive.
After '16 the running board mounting bolts used lock washers and I'm sure more were used in later years.
The wood coilboxes used lockwashers atop the 10 porcelains.
There are lock washers on the screws for the windshield hinge to glass frames on my '13 touring.
Lock washers in lieu of cotter pins on the crankcase pan to block bolts. Factory made the change about early 1924.
Are they all split washers (be careful how you accent that) or other types, too?
FEB 2 Acc. 94, "Bolts, Nuts, etc." folder, Ford Archives
Letter from W.C. Klann to Martin and Howard:
"On Dec. 2nd, 1924 Mr. Martin and Mr.. Galamb O.K.'d building motors with no cotter keys in the bolts but using lock washers instead in the crankcase, transmission cover and cylinder block assembly only. Why not put this on the blue print? Please advise."
From http://www.mtfca.com/encyclo/doc25.htm
Some folks have analoculosis and can not stand to have modern things on their cars while insisting they be period correct. If you have a cotter pin on your crank case engine pan bolt it will be difficult to stop an oil leak. If you want a trailer queen then by all means do it right. If you want a driver then make it easy on yourself.
I agree with Frank Harris. When working on a T there are some nuts and bolts that are fairly hard to get to.
I can remember when I was in my 20's trying to get the gas tank off my 24 Coupe.
Man I cussed those original bolts that hadent moved in 50+ years and trying to wrestle the cotter pins out of the bolt so I could remove the nut.
These days in the hard to reach places I install lock washers, and its so much easier. I say fooey on trying to be 150% correct since all of my cars are 95% original decent looking drivers.
BUT to each their own.