Solutions for Whitworth thread tripod mounts [Archive]

Sevo

11-Mar-2013, 06:31

What is your problem? Or rather. are you sure that it is Whitworth related? 1/4, 3/8 and 5/8 UNC (the threads commonly used on modern tripods) dimensions are close enough to the corresponding Whitworth threads to be mutually exchangeable, at least for any screw length you might need on a tripod.

Jac@stafford.net

11-Mar-2013, 07:37

How unusual! Is it a home-made camera?

I would take it to a good hardware store and simply try various bolts to determine its actual dimensions. If it is a Whitworth size, I would change out the socket for a 3/8. For a socket look into 'T' nut fasteners such as this one: http://www.churchfurniturestore.com/tnut.jpg

Best of luck!

Robert Bowring

11-Mar-2013, 07:52

Be careful when trying another bolt. You may find one that may be close but don't force anything or you could bugger it up. If is truly a Whitworth size it will have a different thread per inch and a different thread angle. Never heard of a camera with a Whitworth tripod screw. Was yours made in England? I think the Brits were the only ones who used Whitworth.

Sevo

11-Mar-2013, 08:10

Be careful when trying another bolt. You may find one that may be close but don't force anything or you could bugger it up. If is truly a Whitworth size it will have a different thread per inch and a different thread angle

UNC and Whitworth have exactly the same TPI, and the nominal 5° difference in angle will be smaller than the variations in UNC tripod threads...

Leigh

11-Mar-2013, 08:18

The 55° Whitworth and 60° American threads are intermatable unless the tolerances are very tight.
Tight tolerances are not appropriate for tripod attachments, so you won't encounter this problem.

Just go ahead and use American 1/4"-20 or 3/8"-16 fasteners and they'll work fine.

Some people have claimed that all tripod fasteners use Whitworth threads. That may be true.

- Leigh

Robert Bowring

11-Mar-2013, 08:27

You are probably correct. The tolerances are probably would be OK for a tripod. I was just going on my experiences restoring British motorcycles. I can't remember how many repairs I have made when someone has used a bolt that was "close" to the correct size.

Leigh

11-Mar-2013, 08:32

The tolerances are probably would be OK for a tripod. I was just going on my experiences restoring British motorcycles. I can't remember how many repairs I have made when someone has used a bolt that was "close" to the correct size.
The problem you usually run into are folks trying to stuff metric fasteners into imperial holes. Some of the thread sizes appear to be the same, but really are not. If you engage two or three threads by hand it may seem OK. Then folks try to tighten it down and think that the resistance they encounter is from rust or dirt, when in fact it's due to the threads not fitting.

This problem occurs most often due to the thread pitches being slightly different.

Both Whitworth and Imperial 1/4"-20 and 3/8"-16 fasteners have identical pitches.

- Leigh

Robert Bowring

11-Mar-2013, 08:46

You are correct. The problem I usually run into is when someone turns the wrong steel bolt into something soft like brass or aluminum. They think it is just a little tight so they keep cranking it in until the threads strip out.

Leigh

11-Mar-2013, 08:49

That's why the good Lord invented Helicoils. :D

- Leigh

Robert Bowring

11-Mar-2013, 09:04

I have had to repair Helicoils too. (lots of fun). Tools can become deadly weapons in the wrong hands.

Jac@stafford.net

11-Mar-2013, 09:20

I think the Brits were the only ones who used Whitworth.

When Triumph Motorcycle decided to switch to more common fasteners, they chose American size, while in America there was an attempt to switch to Metrics! Go figure. (I had one of the rare Rickman Brothers' Rickman-Tridents. American fasteners except for a few which were Russian of a size nobody could match.)

Leigh

11-Mar-2013, 09:26

... a few which were Russian of a size nobody could match.)
Of course there are innumerable examples of proprietary threads in industry.

The most obvious one in photography is the Leica thread, which is 39mm with a 26tpi Whitworth thread.

- Leigh

Robert Bowring

11-Mar-2013, 09:38

My 1977 Bonneville has American, Whitworth and some metric. I always have the wrong wrench.

Steve Smith

11-Mar-2013, 12:34

How unusual! Is it a home-made camera?

What's unusual? Cameras traditionally had 1/4" and 3/8" Whitworth threads.

Some people have claimed that all tripod fasteners use Whitworth threads. That may be true.

Yes. I am one of those people! (well, not all... not now anyway).

From that fount of all knowledge, Wikipedia:

Screw thread

Per ISO 1222:2010, the current tripod screw thread standard for attaching the camera calls for a 1/4-20 UNC[2] or 3/8-16 UNC thread. Most consumer cameras are fitted with 1/4-20 UNC threads. Larger, professional cameras and lenses may be fitted with 3/8-16 UNC threads, plus a removable 1/4-20 UNC adapter, allowing them to be mounted on a tripod using either standard.

Historically, the thread standard for attaching older cameras to tripods was 1/4-20 BSW for smaller cameras or 3/8-16 BSW for larger cameras and pan/tilt heads. In this application the BSW and UNC thread profiles are similar enough that one can mount a modern camera on a legacy tripod and vice versa.

I think cameras with 1/4" BSF threads existed before UNC was unified and I don't see why German camera manufacturers would have used an American thread when they could use one in use throughout the whole of the British Empire!

It's very likely that tripod manufacturers use a thread optimised (I mean compromised) to fit both without causing problems. A while ago I found one tripod manufacturer who specified UNC and another using BSW (but I can't remember which manufacturers now).

Steve.

Jac@stafford.net

11-Mar-2013, 12:46

What's unusual? Cameras traditionally had 1/4" and 3/8" Whitworth threads.

You are right. In fact, I think you corrected me on this once before. The 1/4 x 20 and 3/8 x 16 we use on camera tripods are Whitworth standards. And the UNC versions are only 1 tpi different.

Thanks again.
Jac

Steve Smith

11-Mar-2013, 12:47

Steve Smith

11-Mar-2013, 12:50

That's why the good Lord invented Helicoils.

There used to be a very good motor engineering company near me. A few years ago a friend took in his van which needed a helicoil fitted in one of the spark plug threads. When he went back to get it he was told that they didn't have a proper helicoil so they had machined one from a nut which fitted the spark plug (M16 I think). It was a superb piece of machining and worked perfectly.

But because they didn't have a proper helicoil in stock, they refused to take any money for doing the job.

Steve.

E. von Hoegh

11-Mar-2013, 12:50

You are right. In fact, I think you corrected me on this once before. The 1/4 x 20 and 3/8 x 16 we use on camera tripods are Whitworth standards. And the UNC versions are only 1 tpi different.

Thanks again.
Jac

Nope. Same thread pitch, almost the same major and minor diameters, and five degrees difference in thread angle.
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.

Steve Smith

11-Mar-2013, 13:07

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

11-Mar-2013, 13:14

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

11-Mar-2013, 13:36

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

11-Mar-2013, 14:17

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

11-Mar-2013, 14:28

The cutting angle changes the tpi, no?

No, it affects the flange profile and inner diameter.

Steve Smith

11-Mar-2013, 14:38

91077

wombat2go

11-Mar-2013, 15:13

Last weekend
91078
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

11-Mar-2013, 15:15

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.
www.fastenal.com/content/feds/pdf/Article%20-%20Screw%20Threads%20Design.pdf

- Leigh

Leigh

11-Mar-2013, 15:21

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

11-Mar-2013, 20:19

. . . 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.

Leigh

11-Mar-2013, 22:11

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.
As I mentioned previously regarding Class of Fit...

Class 1A is the loosest, and thus most likely to intermate successfully with BSW.

- Leigh

Sevo

11-Mar-2013, 23:44

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.

That might have been a US/British only definition, the Unified thread series was still quite new at that time. I can't locate the German/DIN tripod screw standard of the period, which could then still have been Whitworth (or the DIN metric definition thereof), as it was some thirty years earlier. In more recent years, the above (or something very similar) evidently has been the ISO definition, but that may have been a consequence of harmonization efforts (and UNC being a ISO adopted standard, while Whitworth is not).

pmalsop

12-Mar-2013, 02:12

$5 later, I have found a Whitword 3/8 bolt that fits the base plate, man they are expensive!
I think I have made a work around to attach the camera to a modern tripod
Watch this space! and thanks for replies

E. von Hoegh

12-Mar-2013, 06:46

The cutting angle changes the tpi, no?

No.

Leigh

12-Mar-2013, 06:56

The cutting angle changes the tpi, no?
No. The flank (cutting) angle changes the depth of the thread, not the pitch (turns per inch).

Thread depth affects the strength of the fastener, but has no other significance.

- Leigh

Jac@stafford.net

12-Mar-2013, 07:38

$5 later, I have found a Whitword 3/8 bolt that fits the base plate, man they are expensive!

:( They are dirt cheap here in the USA. Maybe you should have not got a Whitworth named fastener.

To others - thanks for the help with my understanding of the standards. Are you machinists? Engineers?

E. von Hoegh

12-Mar-2013, 07:42

:( They are dirt cheap here in the USA. Maybe you should have not got a Whitworth named fastener.

To others - thanks for the help with my understanding of the standards. Are you machinists? Engineers?

Practitioner of Obsolete Technology, specialising in watchmaking, hollow-state electronics, antique internal combustion devices, etc etc..

Leigh

12-Mar-2013, 07:53

Are you machinists? Engineers?
I'm a machinist (early career) and an engineer later on.

- Leigh

Jim Jones

12-Mar-2013, 07:59

. . . To others - thanks for the help with my understanding of the standards. Are you machinists? Engineers?

Another former hollow state-technician with practice in correcting the mistakes of electrical and mechanical engineers, and 60+ years of wasting hours improvising something that would cost a dollar. Leigh, I respect most engineers, but when they do screw up, WOW!