While we have pretty well covered the size of the Steering Wheel Nut thread, little more has been noted in regard to other Specifications. To try to expand on what has been noted, I decided to do a little "in depth research on Steering Wheel Nuts. In order to document this, I used the following of my resources ; 1967 Mustang Factory Chassis Assembly Manual (my 1957,1959 and 1966 Assembly Manuals do not include Chassis); 1949-59, 1960-64, 1960-68, 1965-72 and 1973-77 Ford Master Parts Catalogs ; single year Ford Parts and Accessories Catalogs (MPC's) from 1955 through 1967 ; and 1954, 1959, 1960, 1961, 1965, 1966, 1969 and 1975 Ford Standard Parts and Utility Catalogs. In order to try to make somewhat logical sense of all of the information, I put it into a spreadsheet (copy attached).
A few comments and items of interest in regard to my findings :
1) All Part Numbers shown are Service Part Numbers. Just happens to be that the
1967 Assembly Manual (Factory) Part Number is the same. Other applications/
years may or may not be the same as the Service Part Numbers.
2) All Steering Wheel Nuts listed have 5/8-18, NF thread.
3) All Steering Wheel Nuts listed require a 15/16" Socket/Wrench.
4) A "Standard" 5/8-18 Hex Nut has a thickness(height) of 35/64" ; a "Standard"
5/8-18 Hex Jam nut has a thickness(height) of 3/8".
5) A "Check Nut" is also known as a "Lock Nut, and/or "Jam Nut", depending on
its use.
6) A "Prevailing Torque Locknut", I believe, is one with "distorted" threads,
similar to what RoyceP described in Reply # 23.
7) Between the mid-sixties and early 90's, I removed around three dozen 1957-59
Steering Wheels ; I do not ever remember any of the Nuts being "Raven" ; only
Plain.
Interestingly, the "Flex-top Locknuts" shown for 1965-66 Mustangs in the
1960-68 and 1965-72 MPC's, do not appear in either the 1965 or 1966 "Single
Year" MPC's. Possibly it was decided after Production that a "Flex-Top Lock-
Nut" would be better ? Since it has been over 35 years since I have had the
Steering Wheel off of my '66, I don't remember, nor did I pay any attention at
the time, as to the type of nut.
Since there is no 1966 Chassis Assembly Manual, and I don't have
a 1965 (which may not help if the change was late), there is no help there.
It would be interesting to see if anyone with a known, or "believed to be"
Original 1965 or 66 has, or has seen one with the Flex-Top Locknut.
9) As Jim noted in his Reply #24, there is no documentation of a "locking nut"
until 1968 (although a "Check Nut" may be considered as one). Like I
mentioned in my Reply #22, on the 1957-59 Fords, I cannot remember ever being able to "spin" a Steering Wheel Nut on like one would with a standard
bolt and nut. I found this to be the case also on my 1967. Makes me wonder ,
since these nuts are listed separately from "Standard Hex Nuts", besides the
thickness, is there also a difference in thread tolerance ; or distorted threads ?
Another possibility, was the threaded end of the Steering Shaft tapered, similar
to that of a pipe thread ? What makes me think of this possibility, is that about
a year ago, I had to move my 1959 Ford Retractable temporarily from its
storage location so that security could be enhanced. I had forgotten that I had
removed its Steering Wheel, and had apparently not left the nut with it. I went
to my local fastener supplier and purchased a 5/8-18 jam nut. After stating the
nut on the shaft for a few threads (to be sure that the threads meshed correctly),
it became hard to turn. I used my 1/2" ratchet with a 15/16 socket, and
eventually was able to get it to tighten against the hub.
It would be very interesting to see the Engineering Drawings for the Steering
Wheel nuts and Shafts.
10) In regard to the locking nuts used from 1968-77, 382412-S, it is interesting
this Part Number does not appear in the 1969 or 1975 Standard and Utility
Parts Catalog. Only the 382412-S100 shows up. Only 382412-S100 (Special)
and 382412-S4 (Raven and Black Paint) are listed. Was the "-S" Assembly
Line only ?
11) Finally, I have attached copies of pages from Standard Parts and Utility
Catalogs that show illustrations and specifications for the four different nuts
noted on the spreadsheet.
I trust that all of this won't drive you "nuts".
Bob