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Is the hardware (nuts and bolts) on our trucks officially labeled as "UNC" (Unified National Coarse) & "UNF" (Unified National Fine) ?
I was looking for a set of thread checkers and wanted to be sure.
Question about our hardware..
Moderators: Cal_Gary, T. Highway, Monkey Man, robi
Re: Question about our hardware..
ORD 9 refers to "NC" National Coarse and "NF" National Fine. It does mention UNF, as "Uniform National Form".
The history of thread forms is an interesting and convoluted subject, but the basic idea is that the Unified thread is a slightly updated version of the old American National thread form. In practice, the two are basically interchangeable. The differences lie in the tolerances in the various thread classes (if you're not familiar with thread specifications, a single thread, e.g. 1/2-13 NC [1/2" major or outside diameter with 13 threads per inch of length] can have different classes, e.g. "1" which is very loose, that describe how well the threads fit together, and why some fasteners may be feel loose while others of the same size and pitch feel tight).
Since the unified standard was adopted shortly after WWII by the UK, Canada, and the USA, our trucks probably have a mix of the old NC and NF, and the newer UNC and UNF. A lot of the components pre-date the unified standard, and were probably not updated by Chrysler, especially since the old and new were mechanically compatible.
Assuming that you're not trying to match thread fitment classes, a thread checker for the older National or the newer Unified should be good. I think you'd have to look hard to find an old thread gage for a National thread spec.
The history of thread forms is an interesting and convoluted subject, but the basic idea is that the Unified thread is a slightly updated version of the old American National thread form. In practice, the two are basically interchangeable. The differences lie in the tolerances in the various thread classes (if you're not familiar with thread specifications, a single thread, e.g. 1/2-13 NC [1/2" major or outside diameter with 13 threads per inch of length] can have different classes, e.g. "1" which is very loose, that describe how well the threads fit together, and why some fasteners may be feel loose while others of the same size and pitch feel tight).
Since the unified standard was adopted shortly after WWII by the UK, Canada, and the USA, our trucks probably have a mix of the old NC and NF, and the newer UNC and UNF. A lot of the components pre-date the unified standard, and were probably not updated by Chrysler, especially since the old and new were mechanically compatible.
Assuming that you're not trying to match thread fitment classes, a thread checker for the older National or the newer Unified should be good. I think you'd have to look hard to find an old thread gage for a National thread spec.
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Re: Question about our hardware..
You Da' man Elwood! Thanks for the info.