[rollei_list] Re: ?? True Sizes of Tripod Mounting Holes

RUGers
As usual, Richard is right. The thread form is 60 degrees, NOT the Whitworth 55 degrees.
The word Whitworth makes my skin crawl, thinking of my early days working on my MG TD, Cad-Allard, Jaguar or AC-Bristol. Al those used a mixture of thread und wrench standards. 
I only reached fastener sanity with Porsche and the Metric system.
Unfortunately, my working life is spent in the only industry that still uses the US Inch standard; the commercial aircraft industry. Yes, even the most advanced airplane in the world, the Boeing 
Dreamliner 787 uses inches.

Jerry


Richard Knoppow wrote:
----- Original Message ----- From: "Frank Dernie" <Frank.Dernie@xxxxxxxxxxxxxx> 
To: <rollei_list@xxxxxxxxxxxxx>
Sent: Tuesday, August 28, 2007 2:51 AM
Subject: [rollei_list] Re: ?? True Sizes of Tripod Mounting Holes


This doesn't help but I thought the two standards were both Whitworth
thread form not UNC.
Frank

On 28 Aug, 2007, at 03:14, Laurence Cuffe wrote:
On Monday, August 27, 2007, at 07:50PM, "SandyF." <sbf70@xxxxxxxx> wrote:
According to the Unified Standards, the following applies to UN Coarse Series Threads 

Size      Basic      Threads/inch   Basic
           Major                            Pitch
           Dia. (in)                        Dia. (in)
1/4-20   0.2500           20          0.2175
3/8-16   0.3750           16          0.3344
The above information straight from my Machinery's Handbook, 21st ed.
S. B. Friedman, aka
SandyF  -----  Ö¿Ö¬


----------------------------------------------------------------------
I found a thread standard in a reprint of a book I think originally printed by the National Camera School. For American cameras the thread was covered by ASA standard PH 3.6-1952 This specifies a 1/4-20 UNC-1A thread according to Unified American Screw Threads B1.1-1949. 
   The standard is slightly different than the one given above by Sandy.

Major Diameter (inches) Pitch Diameter (inches) Minor Diameter (inches
Max   0.2489            0.2164                  0.1876
Min   0.2367            0.2108                  ------

Recommended length: Small cameras = 0.175"; Large cameras, 0.340"
The standard also has a recommendation for an oversize thread to account for build up during plating. 

   Screw Socket Dimensions: 1/4-20 UNC-1B
Minor Diameter (inches)  Pitch Diameter (inches)  Major Diameter (inches)
Min    0.1959            0.2175                   0.2500
Max    0.2067            0.2248                   ------
A second ASA standard, ASA PH3.7-1952, applies to heavy duty cameras and European cameras. The thread specified is: 3/8-Inch-16 UNC-1A American Unified Screw Threads ASA B1.1-1949 with the following dimensions: 

Major Diameter (inches  Pitch Diameter (inches) Minor Diameter (inches
Max  0.3737             0.3331                  0.2970
Min  0.3595             0.3266                  ------

Screw Socket Dimensions: 3/8-inch 16 UNC-1B according to PH B1.1-1949

Minor Diameter (inches)  Pitch Diameter (inches)  Major Diameter (inches
Min   0.9373             0.3344                   0.3750
Max   0.3182             0.3429                   ------
This standard also gives recommended dimensions for a thread adaptor to the American size thread. 

------------------

---
Richard Knoppow
Los Angeles, CA, USA
dickburk@xxxxxxxxxxxxx

---
R


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