Solutions for Whitworth thread tripod mounts

[Steve Smith]

But I find it hard to believe that every camera and tripod maker ordered Whitworth standard tooling, especially when 1/4-20 (stovebolt) and likely 3/16-24 (carriage bolt) both predate the adoption of the Unified standard in this country.

That's because you are thinking from a US perspective. British and German manufacturers would definitely have used Whitworth as it was in worldwide use (except the US probably!).

EDIT: And I would bet that the pre-unified 1/4-20 stove bolt was based on the Whitworth thread.


Steve.

[E. von Hoegh]

That's because you are thinking from a US perspective. British and German manufacturers would definitely have used Whitworth as it was in worldwide use (except the US probably!).


Steve.

But it also means that both of my tripods (New York and New Jersey), and my 8x10 (Chicago) will almost certainly have UNC threads. I agree that British and Continental, perhaps also Japanese manufacturers would have gone with BSW threads, at least during a certain era. I have noticed that the tripod sockets on my '60s and '70s Nikon stuff are specified as 1/4-20 (UNC) according to the original literature.

[Sevo]

That's because you are thinking from a US perspective. British and German manufacturers would definitely have used Whitworth as it was in worldwide use (except the US probably!).

Besides being a British invention, Whitworth actually was a DIN norm and in wide use in Germany. Even though Germany was early at metrication, various "Zoll" units for threads and pipe diameters survived until recent years (and the regional variations eventually were harmonized with the Imperial system). Some relics still are around e.g. in plumbing.

[Jac@stafford.net]

The TPI is the same. 20 for 1/4" and 16 for 3/8. Only the cutting angle differs by five degrees.

The cutting angle changes the tpi, no?

[Sevo]

The cutting angle changes the tpi, no?

No, it affects the flange profile and inner diameter.

[Steve Smith]

[wombat2go]

Last weekend

I made a batch of adaptors for the Slik 700 tripod on the lathe. The adaptors are tapped 1/4 20 UNC and the studs are of all-thread.
I made the studs longer than the original . The studs are bottomed out finger tight in the camera then the adaptor is screwed on.

[Leigh]

The important parameter that has not been mentioned is the "Class of Fit".
This is a measure of the amount of space that exists between the male and female fasteners.

By using one of the looser classes of fit, BSW and UNC will live happily and snugly together for eternity.

Class of Fit is defined for fasteners at nominal dimension. It should not be confused with tolerance.

For those interested, here's a short PDF from Fastenal that explains thread characteristics.
http://www.fastenal.com/content/feds...s%20Design.pdf

- Leigh

[Leigh]

The studs are bottomed out finger tight in the camera then the adaptor is screwed on.

Be very careful about bottoming out fasteners in cameras. Many are not designed for that.

Back when I was repairing Nikons, much of our work was repairing cameras that had been damaged by extended tripod screws breaking through the base fitting and damaging internal parts.

- Leigh

[Jim Jones]

. . . Cameras traditionally had 1/4" and 3/8" Whitworth threads.

Steve.

According to 1952 American Standards Association data sheets, tripod connections for American cameras are 1/4 inch 20 TPI UNC-1A and 3/8 inch 16 TPI UNC-1A. The recommended maximum protrusion of the 1/4 inch screw was 0.175 inch for light cameras and 0.340 inch for heavy cameras. Some cameras, such as some models of Burke & James, needed that long protrusion, and the screws on their tripods protruded too far to be safe on light cameras as Leigh may have encountered. I don't have ASA standards later than 1952, or official specs for other countries.